python/api2/py2ApiMeshShape.py

#-
# ===========================================================================
# Copyright 2020 Autodesk, Inc.  All rights reserved.
#
# Use of this software is subject to the terms of the Autodesk license
# agreement provided at the time of installation or download, or which
# otherwise accompanies this software in either electronic or hard copy form.
# ===========================================================================
#+

from builtins import object
from builtins import next
from builtins import range
import sys, math, ctypes, collections
import maya.api.OpenMaya as om
import maya.api.OpenMayaUI as omui
import maya.api.OpenMayaRender as omr

def maya_useNewAPI():
    """
    The presence of this function tells Maya that the plugin produces, and
    expects to be passed, objects created using the Maya Python API 2.0.
    """
    pass

## helper function
def useSelectHighlight(selectedList, path):
    
    displayStatus = omr.MGeometryUtilities.displayStatus(path)
    if displayStatus == omr.MGeometryUtilities.kHilite or displayStatus == omr.MGeometryUtilities.kActiveComponent:
        return True
    
    pathCopy = om.MDagPath(path)

    while pathCopy.length() > 0:
        if selectedList.hasItem(pathCopy):
            return True
        pathCopy.pop()

    return False

def floatApproxEqual(left, right):
    return abs(left - right) < 0.0001

################################################################################
##
## This class holds the underlying geometry for the shape or data.
## This is where geometry specific data and methods should go.
##
################################################################################
class apiMeshGeomUV(object):
    def __init__(self, other=None):
        if other:
            self.copy(other)
        else:
            self.reset()

    def uvId(self, fvi):
        return self.faceVertexIndex[fvi]

    def getUV(self, uvId):
        return [ self.ucoord[uvId], self.vcoord[uvId] ]

    def u(self, uvId):
        return self.ucoord[uvId]

    def v(self, uvId):
        return self.vcoord[uvId]

    def uvcount(self):
        return len(self.ucoord)

    def append_uv(self, u, v):
        self.ucoord.append( u ) 
        self.vcoord.append( v ) 

    def reset(self):
        self.ucoord = om.MFloatArray()
        self.vcoord = om.MFloatArray()
        self.faceVertexIndex = om.MIntArray()

    def copy(self, other):
        self.ucoord = om.MFloatArray(other.ucoord)
        self.vcoord = om.MFloatArray(other.vcoord)
        self.faceVertexIndex = om.MIntArray(other.faceVertexIndex)

class apiMeshGeom(object):
    def __init__(self):
        self.vertices = om.MPointArray()
        self.face_counts = om.MIntArray()
        self.face_connects = om.MIntArray()
        self.normals = om.MVectorArray()
        self.uvcoords = apiMeshGeomUV()
        self.faceCount = 0

    def copy(self, other):
        self.vertices = om.MPointArray(other.vertices)
        self.face_counts = om.MIntArray(other.face_counts)
        self.face_connects = om.MIntArray(other.face_connects)
        self.normals = om.MVectorArray(other.normals)
        self.uvcoords = apiMeshGeomUV(other.uvcoords)
        self.faceCount = other.faceCount

################################################################################
##
## Provides a data type for some arbitrary user geometry.
## 
## A users geometry class can exist in the DAG by creating an
## MPxSurfaceShape (and UI) class for it and can also be passed through
## DG connections by creating an MPxGeometryData class for it.
## 
## MPxGeometryData is the same as MPxData except it provides 
## additional methods to modify the geometry data via an iterator.
##
################################################################################
## Ascii file IO defines
##
kDblQteChar     = "\""
kSpaceChar      = " "
kWrapString     = "\n\t\t"
kVertexKeyword  = "v"
kNormalKeyword  = "vn"
kTextureKeyword = "vt"
kFaceKeyword    = "face"
kUVKeyword      = "uv" 

class apiMeshGeomIterator(om.MPxGeometryIterator):
    def __init__(self, userGeometry, components):
        om.MPxGeometryIterator.__init__(self, userGeometry, components)
        self.geometry = userGeometry
        self.reset()

    def reset(self):
        ## Resets the iterator to the start of the components so that another
        ## pass over them may be made.
        ##
        om.MPxGeometryIterator.reset(self)
        self.currentPoint = 0
        if self.geometry:
            maxVertex = len(self.geometry.vertices)
            self.maxPoints = maxVertex

    def point(self):
        ## Returns the point for the current element in the iteration.
        ## This is used by the transform tools for positioning the
        ## manipulator in component mode. It is also used by deformers.
        ##
        pnt = om.MPoint()
        if self.geometry:
            pnt = self.geometry.vertices[ self.index() ]
        return pnt

    def setPoint(self, pnt):
        ## Set the point for the current element in the iteration.
        ## This is used by deformers.
        ##
        if self.geometry:
            self.geometry.vertices[ self.index() ] = pnt

    def iteratorCount(self):
        ## Return the number of vertices in the iteration.
        ## This is used by deformers such as smooth skinning
        ##
        if self.geometry:
            return len(self.geometry.vertices)
        return 0

    def hasPoints(self):
        ## Returns true since the shape data has points.
        ##
        return True

class apiMeshData(om.MPxGeometryData):
    typeName = "apiMeshData"
    id = om.MTypeId(0x80778)

    @staticmethod
    def creator():
        return apiMeshData()

    def __init__(self):
        om.MPxGeometryData.__init__(self)
        self.fGeometry = apiMeshGeom()

    def __del__(self):
        self.fGeometry = None

    def readASCII(self, argList, idx):
        idx = self.readVerticesASCII(argList, idx)
        idx = self.readNormalsASCII(argList, idx)
        idx = self.readFacesASCII(argList, idx)
        idx = self.readUVASCII(argList, idx)
        return idx

    def readBinary(self, inputData, length):
        ## not implemented
        return 0

    def writeASCII(self):
        data  = self.writeVerticesASCII()
        data += self.writeNormalsASCII()
        data += self.writeFacesASCII()
        data += self.writeUVASCII()
        return data

    def writeBinary(self):
        ## not implemented
        return bytearray()

    def copy(self, src):
        self.fGeometry.copy(src.fGeometry)
    
    def typeId(self):
        return apiMeshData.id

    def name(self):
        return apiMeshData.typeName

    ##################################################################
    ##
    ## Overrides from MPxGeometryData
    ##
    ##################################################################

    def iterator(self, componentList, component, useComponents, world=None):
        if useComponents:
            return apiMeshGeomIterator(self.fGeometry, componentList)

        return apiMeshGeomIterator(self.fGeometry, component)
    
    ##################################################################
    ##
    ## Helper methods
    ##
    ##################################################################

    def readVerticesASCII(self, argList, idx):
        geomStr = ""
        try:
            geomStr = argList.asString(idx)
        except:
            geomStr = ""
            pass

        if geomStr == kVertexKeyword:
            idx = argList.lastArgUsed()+1
            vertexCount = argList.asInt(idx)
            idx = argList.lastArgUsed()+1
            for i in range(vertexCount):
                vertex = argList.asPoint(idx)
                idx = argList.lastArgUsed()+1
                self.fGeometry.vertices.append(vertex)

        return idx

    def readNormalsASCII(self, argList, idx):
        geomStr = ""
        try:
            geomStr = argList.asString(idx)
        except:
            geomStr = ""
            pass

        if geomStr == kNormalKeyword:
            idx = argList.lastArgUsed()+1
            normalCount = argList.asInt(idx)
            idx = argList.lastArgUsed()+1
            for i in range(normalCount):
                normal = argList.asVector(idx)
                idx = argList.lastArgUsed()+1
                self.fGeometry.normals.append(normal)

        return idx

    def readFacesASCII(self, argList, idx):
        geomStr = ""
        try:
            geomStr = argList.asString(idx)
        except:
            geomStr = ""
            pass

        while geomStr == kFaceKeyword:
            idx = argList.lastArgUsed()+1
            faceCount = argList.asInt(idx)
            idx = argList.lastArgUsed()+1
            self.fGeometry.face_counts.append(faceCount)
            for i in range(faceCount):
                vid = argList.asInt(idx)
                idx = argList.lastArgUsed()+1
                self.fGeometry.face_connects.append(vid)

            try:
                geomStr = argList.asString(idx)
            except:
                geomStr = ""
                pass

        self.fGeometry.faceCount = len(self.fGeometry.face_counts)
        return idx

    def readUVASCII(self, argList, idx):
        self.fGeometry.uvcoords.reset()

        geomStr = ""
        try:
            geomStr = argList.asString(idx)
        except:
            geomStr = ""
            pass

        if geomStr == kUVKeyword:
            idx = argList.lastArgUsed()+1
            uvCount = argList.asInt(idx)
            idx = argList.lastArgUsed()+1
            faceVertexListCount = argList.asInt(idx)
            idx = argList.lastArgUsed()+1
            for i in range(uvCount):
                u = argList.asDouble(idx)
                idx = argList.lastArgUsed()+1
                v = argList.asDouble(idx)
                idx = argList.lastArgUsed()+1
                self.fGeometry.uvcoords.append_uv(u, v)

            for i in range(faceVertexListCount):
                fvi = argList.asInt(idx)
                idx = argList.lastArgUsed()+1
                self.fGeometry.uvcoords.faceVertexIndex.append( fvi )

        return idx

    def writeVerticesASCII(self):
        vertexCount = len(self.fGeometry.vertices)

        data  = "\n"
        data += kWrapString
        data += kDblQteChar + kVertexKeyword + kDblQteChar + kSpaceChar + str(vertexCount)

        for i in range(vertexCount):
            vertex = self.fGeometry.vertices[i]

            data += kWrapString
            data += str(vertex[0]) + kSpaceChar + str(vertex[1]) + kSpaceChar + str(vertex[2])

        return data

    def writeNormalsASCII(self):
        normalCount = len(self.fGeometry.normals)

        data  = "\n"
        data += kWrapString
        data += kDblQteChar + kNormalKeyword + kDblQteChar + kSpaceChar + str(normalCount)

        for i in range(normalCount):
            normal = self.fGeometry.normals[i]

            data += kWrapString
            data += str(normal[0]) + kSpaceChar + str(normal[1]) + kSpaceChar + str(normal[2])

        return data

    def writeFacesASCII(self):
        numFaces = len(self.fGeometry.face_counts)

        data = ""
        vid = 0

        for i in range(numFaces):
            faceVertexCount = self.fGeometry.face_counts[i]

            data += "\n"
            data += kWrapString
            data += kDblQteChar + kFaceKeyword + kDblQteChar + kSpaceChar + str(faceVertexCount)

            data += kWrapString

            for v in range(faceVertexCount):
                value = self.fGeometry.face_connects[vid]

                data += str(value) + kSpaceChar
                vid += 1

        return data

    def writeUVASCII(self):
        uvCount = self.fGeometry.uvcoords.uvcount()
        faceVertexCount = len(self.fGeometry.uvcoords.faceVertexIndex)

        data = ""

        if uvCount > 0:
            data  = "\n"
            data += kWrapString
            data += kDblQteChar + kUVKeyword + kDblQteChar + kSpaceChar + str(uvCount) + kSpaceChar + str(faceVertexCount)

            for i in range(uvCount):
                uv = self.fGeometry.uvcoords.getUV(i)

                data += kWrapString
                data += str(uv[0]) + kSpaceChar + str(uv[1]) + kSpaceChar

            for i in range(faceVertexCount):
                value = self.fGeometry.uvcoords.faceVertexIndex[i]

                data += kWrapString
                data += str(value) + kSpaceChar

        return data


################################################################################
##
## apiMeshShape
##
## Implements a new type of shape node in maya called apiMesh.
##
## INPUTS
##     inputSurface    - input apiMeshData
##     outputSurface   - output apiMeshData
##     worldSurface    - array of world space apiMeshData, each element
##                       represents an istance of the shape
## OUTPUTS
##     mControlPoints  - inherited control vertices for the mesh. These values
##                       are tweaks (offsets) that will be applied to the
##                       vertices of the input shape.
##     bboxCorner1     - bounding box upper left corner
##     bboxCorner2     - bounding box lower right corner
##
################################################################################
class apiMesh(om.MPxSurfaceShape):
    sNodeName = "apiMesh_py"
    sDrawRegistrantId = "apiMeshPlugin_py"

    ##########################################################
    ##
    ## Attributes
    ##
    ##########################################################
    inputSurface = None
    outputSurface = None
    worldSurface = None

    useWeightedTransformUsingFunction = None
    useWeightedTweakUsingFunction = None

    ## used to support tweaking of points, the inputSurface attribute data is
    ## transferred into the cached surface when it is dirty. The control points
    ## tweaks are added into it there.
    ##
    cachedSurface = None

    bboxCorner1 = None
    bboxCorner2 = None

    enableNumericDisplay = None

    @staticmethod
    def creator():
        return apiMesh()

    @staticmethod
    def initialize():
        typedAttr = om.MFnTypedAttribute()
        numericAttr = om.MFnNumericAttribute()

        ## ----------------------- INPUTS --------------------------
        apiMesh.inputSurface = typedAttr.create( "inputSurface", "is", apiMeshData.id, om.MObject.kNullObj )
        typedAttr.storable = False
        om.MPxNode.addAttribute( apiMesh.inputSurface )

        apiMesh.useWeightedTransformUsingFunction = numericAttr.create( "useWeightedTransformUsingFunction", "utru", om.MFnNumericData.kBoolean, True )
        numericAttr.keyable = True
        om.MPxNode.addAttribute( apiMesh.useWeightedTransformUsingFunction )

        apiMesh.useWeightedTweakUsingFunction = numericAttr.create( "useWeightedTweakUsingFunction", "utwu", om.MFnNumericData.kBoolean, True )
        numericAttr.keyable = True
        om.MPxNode.addAttribute( apiMesh.useWeightedTweakUsingFunction )

        enableNumericDisplay = numericAttr.create( "enableNumericDisplay", "end", om.MFnNumericData.kBoolean, True )
        numericAttr.keyable = True
        om.MPxNode.addAttribute( enableNumericDisplay )

        ## ----------------------- OUTPUTS -------------------------

        ## bbox attributes
        ##
        apiMesh.bboxCorner1 = numericAttr.create( "bboxCorner1", "bb1", om.MFnNumericData.k3Double, 0 )
        numericAttr.array = False
        numericAttr.usesArrayDataBuilder = False
        numericAttr.hidden = False
        numericAttr.keyable = False
        om.MPxNode.addAttribute( apiMesh.bboxCorner1 )

        apiMesh.bboxCorner2 = numericAttr.create( "bboxCorner2", "bb2", om.MFnNumericData.k3Double, 0 )
        numericAttr.array = False
        numericAttr.usesArrayDataBuilder = False
        numericAttr.hidden = False
        numericAttr.keyable = False
        om.MPxNode.addAttribute( apiMesh.bboxCorner2 )

        ## local/world output surface attributes
        ##
        apiMesh.outputSurface = typedAttr.create( "outputSurface", "os", apiMeshData.id, om.MObject.kNullObj )
        typedAttr.writable = False
        om.MPxNode.addAttribute( apiMesh.outputSurface )

        apiMesh.worldSurface = typedAttr.create( "worldSurface", "ws", apiMeshData.id, om.MObject.kNullObj )
        typedAttr.cached = False
        typedAttr.writable = False
        typedAttr.array = True
        typedAttr.usesArrayDataBuilder = True
        typedAttr.disconnectBehavior = om.MFnAttribute.kDelete
        typedAttr.worldSpace = True
        om.MPxNode.addAttribute( apiMesh.worldSurface )

        ## Cached surface used for file IO
        ##
        apiMesh.cachedSurface = typedAttr.create( "cachedSurface", "cs", apiMeshData.id, om.MObject.kNullObj )
        typedAttr.readable = True
        typedAttr.writable = True
        typedAttr.storable = True
        om.MPxNode.addAttribute( apiMesh.cachedSurface )

        ## ---------- Specify what inputs affect the outputs ----------
        ##
        om.MPxNode.attributeAffects( apiMesh.inputSurface, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( apiMesh.inputSurface, apiMesh.worldSurface )
        om.MPxNode.attributeAffects( apiMesh.outputSurface, apiMesh.worldSurface )
        om.MPxNode.attributeAffects( apiMesh.inputSurface, apiMesh.bboxCorner1 )
        om.MPxNode.attributeAffects( apiMesh.inputSurface, apiMesh.bboxCorner2 )
        om.MPxNode.attributeAffects( apiMesh.cachedSurface, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( apiMesh.cachedSurface, apiMesh.worldSurface )

        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlPoints, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueX, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueY, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueZ, apiMesh.outputSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlPoints, apiMesh.cachedSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueX, apiMesh.cachedSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueY, apiMesh.cachedSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueZ, apiMesh.cachedSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlPoints, apiMesh.worldSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueX, apiMesh.worldSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueY, apiMesh.worldSurface )
        om.MPxNode.attributeAffects( om.MPxSurfaceShape.mControlValueZ, apiMesh.worldSurface )

    def __init__(self):
        om.MPxSurfaceShape.__init__(self)

    ##########################################################
    ##
    ## Overrides
    ##
    ##########################################################

    ## From MPxNode
    ##
    def postConstructor(self):
        ##
        ## Description
        ##
        ##    When instances of this node are created internally, the MObject associated
        ##    with the instance is not created until after the constructor of this class
        ##    is called. This means that no member functions of MPxSurfaceShape can
        ##    be called in the constructor.
        ##    The postConstructor solves this problem. Maya will call this function
        ##    after the internal object has been created.
        ##    As a general rule do all of your initialization in the postConstructor.
        ##

        ## This call allows the shape to have shading groups assigned
        ##
        self.isRenderable = True

        ## Is there input history to this node
        ##
        self.fHasHistoryOnCreate = False

        ## Is the shape dirty? Used by VP2.0 sub-scene evaluator
        ##
        self.fShapeDirty = True
        self.fMaterialDirty = True

    def compute(self, plug, datablock):
        ##
        ## Description
        ##
        ##    When input attributes are dirty this method will be called to
        ##    recompute the output attributes.
        ##
        ## Arguments
        ##
        ##    plug      - the attribute that triggered the compute
        ##    datablock - the nodes data
        ##

        if plug == apiMesh.outputSurface:
            return self.computeOutputSurface( plug, datablock )

        elif plug == apiMesh.cachedSurface:
            return self.computeOutputSurface( plug, datablock )

        elif plug == apiMesh.worldSurface:
            return self.computeWorldSurface( plug, datablock )

        else:
            # Let the Maya parent class compute the plug
            return None

    def preEvaluation(self, context, evaluationNode):
        ##
        ## Description
        ##
        ##    Pre evaluate will mark the shape as dirty
        ##    PreEvaluate will be called before each evaluation of this node 
        ##
        ## Arguments
        ##
        ##    context        - Evaluation context in which the compute happen
        ##    evaluationNode - contains information about the dirtyness of plugs
        ##
        if context.isNormal():
            if evaluationNode.dirtyPlugExists(apiMesh.inputSurface) or evaluationNode.dirtyPlugExists(apiMesh.mControlPoints):
                self.setShapeDirty()

    def postEvaluation(self, context, evaluationNode, evalType):
        ##
        ## Description
        ##
        ##    Post evaluate will signal viewport dirty so that renderer can pick it up
        ##    PostEvaluate will be called before each evaluation of this node 
        ##
        ## Arguments
        ##
        ##    context        - Evaluation context in which the compute happen
        ##    evaluationNode - contains information about the dirtyness of plugs
        ##    evalType       - type of evaluation that was performed
        ##
        if context.isNormal():
            if evaluationNode.dirtyPlugExists(apiMesh.inputSurface) or evaluationNode.dirtyPlugExists(apiMesh.mControlPoints):
                self.notifyViewport()

    def setDependentsDirty(self, plug, plugArray):
        ##
        ## Description
        ##
        ##  Horribly abuse the purpose of this method to notify the Viewport 2.0
        ##  renderer that something about this shape has changed and that it should
        ##  be retranslated.
        ##

        ## if the dirty attribute is the output mesh then we need to signal the
        ## the renderer that it needs to update the object

        if plug == apiMesh.inputSurface or plug == om.MPxSurfaceShape.mControlPoints or plug == om.MPxSurfaceShape.mControlValueX or plug == om.MPxSurfaceShape.mControlValueY or plug == om.MPxSurfaceShape.mControlValueZ:
            self.signalDirtyToViewport()

    def getInternalValue(self, plug, handle):
        ##
        ## Description
        ##
        ##    Handle internal attributes.
        ##
        ##    Attributes that require special storage, bounds checking,
        ##    or other non-standard behavior can be marked as "Internal" by
        ##    using the "MFnAttribute.setInternal" method.
        ##
        ##    The get/setInternalValue methods will get called for internal
        ##    attributes whenever the attribute values are stored or retrieved
        ##    using getAttr/setAttr or MPlug getValue/setValue.
        ##
        ##    The inherited attribute mControlPoints is internal and we want
        ##    its values to get stored only if there is input history. Otherwise
        ##    any changes to the vertices are stored in the cachedMesh and outputMesh
        ##    directly.
        ##
        ##    If values are retrieved then we want the controlPoints value
        ##    returned if there is history, this will be the offset or tweak.
        ##    In the case of no history, the vertex position of the cached mesh
        ##    is returned.
        ##
        isOk = True

        if plug == om.MPxSurfaceShape.mControlPoints or plug == om.MPxSurfaceShape.mControlValueX or plug == om.MPxSurfaceShape.mControlValueY or plug == om.MPxSurfaceShape.mControlValueZ:
            ## If there is input history then the control point value is
            ## directly returned. This is the tweak or offset that
            ## was applied to the vertex.
            ##
            ## If there is no input history then return the actual vertex
            ## position and ignore the controlPoints attribute.
            ##
            if self.hasHistory():
                return om.MPxNode.getInternalValue(self, plug, handle)

            else:
                if plug == om.MPxSurfaceShape.mControlPoints and not plug.isArray():
                    index = plug.logicalIndex()
                    pnt = self.getPointValue(index)
                    handle.set3Double( pnt[0], pnt[1], pnt[2] )

                elif plug == om.MPxSurfaceShape.mControlValueX:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    val = self.getChannelValue( index, 0 )
                    handle.setDouble( val )

                elif plug == om.MPxSurfaceShape.mControlValueY:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    val = self.getChannelValue( index, 1 )
                    handle.setDouble( val )

                elif plug == om.MPxSurfaceShape.mControlValueZ:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    val = self.getChannelValue( index, 2 )
                    handle.setDouble( val )

        ## This inherited attribute is used to specify whether or
        ## not this shape has history. During a file read, the shape
        ## is created before any input history can get connected.
        ## This attribute, also called "tweaks", provides a way to
        ## for the shape to determine if there is input history
        ## during file reads.
        ##
        elif plug == om.MPxSurfaceShape.mHasHistoryOnCreate:
            handle.setBool( self.fHasHistoryOnCreate )

        else:
            isOk = om.MPxSurfaceShape.getInternalValue(self, plug, handle)

        return isOk

    def setInternalValue(self, plug, handle):
        ##
        ## Description
        ##
        ##    Handle internal attributes.
        ##
        ##    Attributes that require special storage, bounds checking,
        ##    or other non-standard behavior can be marked as "Internal" by
        ##    using the "MFnAttribute.setInternal" method.
        ##
        ##    The get/setInternalValue methods will get called for internal
        ##    attributes whenever the attribute values are stored or retrieved
        ##    using getAttr/setAttr or MPlug getValue/setValue.
        ##
        ##    The inherited attribute mControlPoints is internal and we want
        ##    its values to get stored only if there is input history. Otherwise
        ##    any changes to the vertices are stored in the cachedMesh and outputMesh
        ##    directly.
        ##
        ##    If values are retrieved then we want the controlPoints value
        ##    returned if there is history, this will be the offset or tweak.
        ##    In the case of no history, the vertex position of the cached mesh
        ##    is returned.
        ##
        isOk = True

        if plug == om.MPxSurfaceShape.mControlPoints or plug == om.MPxSurfaceShape.mControlValueX or plug == om.MPxSurfaceShape.mControlValueY or plug == om.MPxSurfaceShape.mControlValueZ:
            ## If there is input history then set the control points value
            ## using the normal mechanism. In this case we are setting
            ## the tweak or offset that will get applied to the input
            ## history.
            ##
            ## If there is no input history then ignore the controlPoints
            ## attribute and set the vertex position directly in the
            ## cachedMesh.
            ##
            if self.hasHistory():
                self.verticesUpdated()
                return om.MPxNode.setInternalValue(self, plug, handle)

            else:
                if plug == om.MPxSurfaceShape.mControlPoints and not plug.isArray():
                    index = plug.logicalIndex()
                    self.setPointValue( index, handle.asDouble3() )

                elif plug == om.MPxSurfaceShape.mControlValueX:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    self.setChannelValue( index, 0, handle.asDouble() )

                elif plug == om.MPxSurfaceShape.mControlValueY:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    self.setChannelValue( index, 1, handle.asDouble() )

                elif plug == om.MPxSurfaceShape.mControlValueZ:
                    parentPlug = plug.parent()
                    index = parentPlug.logicalIndex()
                    self.setChannelValue( index, 2, handle.asDouble() )

        ## This inherited attribute is used to specify whether or
        ## not this shape has history. During a file read, the shape
        ## is created before any input history can get connected.
        ## This attribute, also called "tweaks", provides a way to
        ## for the shape to determine if there is input history
        ## during file reads.
        ##
        elif plug == om.MPxSurfaceShape.mHasHistoryOnCreate:
            self.fHasHistoryOnCreate = handle.asBool()

        else:
            isOk = om.MPxSurfaceShape.setInternalValue(self, plug, handle)

        return isOk

    def connectionMade(self, plug, otherPlug, asSrc):
        ##
        ## Description
        ##
        ##    Whenever a connection is made to this node, this method
        ##    will get called.
        ##

        if plug == apiMesh.inputSurface:
            thisObj = self.thisMObject()
            historyPlug = om.MPlug( thisObj, om.MPxSurfaceShape.mHasHistoryOnCreate )
            historyPlug.setBool( True )
        else:
            thisObj = self.thisMObject()
            dgNode = om.MFnDependencyNode( thisObj )
            instObjGroups = dgNode.findPlug("instObjGroups", True)
            if plug == instObjGroups:
                self.setMaterialDirty(True)

        return om.MPxNode.connectionMade(self, plug, otherPlug, asSrc )

    def connectionBroken(self, plug, otherPlug, asSrc):
        ##
        ## Description
        ##
        ##    Whenever a connection to this node is broken, this method
        ##    will get called.
        ##

        if plug == apiMesh.inputSurface:
            thisObj = self.thisMObject()
            historyPlug = om.MPlug( thisObj, om.MPxSurfaceShape.mHasHistoryOnCreate )
            historyPlug.setBool( False )
        else:
            thisObj = self.thisMObject()
            dgNode = om.MFnDependencyNode( thisObj )
            instObjGroups = dgNode.findPlug("instObjGroups", True)
            if plug == instObjGroups:
                self.setMaterialDirty(True)

        return om.MPxNode.connectionBroken(self, plug, otherPlug, asSrc )

    def shouldSave(self, plug):
        ##
        ## Description
        ##
        ##    During file save this method is called to determine which
        ##    attributes of this node should get written. The default behavior
        ##    is to only save attributes whose values differ from the default.
        ##

        result = True

        if plug == om.MPxSurfaceShape.mControlPoints or plug == om.MPxSurfaceShape.mControlValueX or plug == om.MPxSurfaceShape.mControlValueY or plug == om.MPxSurfaceShape.mControlValueZ:
            if self.hasHistory():
                ## Calling this will only write tweaks if they are
                ## different than the default value.
                ##
                result = om.MPxNode.shouldSave(self, plug)

            else:
                result = False

        elif plug == apiMesh.cachedSurface:
            if self.hasHistory():
                result = False

            else:
                data = plug.asMObject()
                result = not data.isNull()

        else:
            result = om.MPxNode.shouldSave(self, plug)

        return result

    ## Attribute to component (components)
    ##
    def componentToPlugs(self, component, list):
        ##
        ## Description
        ##
        ##    Converts the given component values into a selection list of plugs.
        ##    This method is used to map components to attributes.
        ##
        ## Arguments
        ##
        ##    component - the component to be translated to a plug/attribute
        ##    list      - a list of plugs representing the passed in component
        ##

        if component.hasFn(om.MFn.kSingleIndexedComponent):
            fnVtxComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(component) )
            thisNode = self.thisMObject()
            plug = om.MPlug( thisNode, om.MPxSurfaceShape.mControlPoints )
            ## If this node is connected to a tweak node, reset the
            ## plug to point at the tweak node.
            ##
            self.convertToTweakNodePlug(plug)

            for i in range(fnVtxComp.elementCount):
                plug.selectAncestorLogicalIndex(fnVtxComp.element(i), plug.attribute())
                list.add(plug)

    def matchComponent(self, item, spec, list):
        ##
        ## Description:
        ##
        ##    Component/attribute matching method.
        ##    This method validates component names and indices which are
        ##    specified as a string and adds the corresponding component
        ##    to the passed in selection list.
        ##
        ##    For instance, select commands such as "select shape1.vtx[0:7]"
        ##    or "select shape1.f[2]" are validated with this method and the
        ##    corresponding component is added to the selection list.
        ##
        ## Arguments
        ##
        ##    item - DAG selection item for the object being matched
        ##    spec - attribute specification object
        ##    list - list to add components to
        ##
        ## Returns
        ##
        ##    the result of the match
        ##

        result = om.MPxSurfaceShape.kMatchOk
        attrSpec = spec[0]
        dim = attrSpec.dimensions
        name = attrSpec.name

        ## Look for attributes specifications of the form :
        ##     vtx[ index ]
        ##     vtx[ lower:upper ]
        ##     f[ index ]
        ##     f[ lower:upper ]
        ##
        if ( (1 == len(spec))and (dim > 0) and ((name == "vtx") or (name == "f")) ):
            
            attrIndex = attrSpec[0]
            
            if (name == "f"):
                numComp  = self.meshGeom().faceCount
                typeComp = om.MFn.kMeshPolygonComponent
            else:
                numComp  = len(self.meshGeom().vertices)
                typeComp = om.MFn.kMeshVertComponent
            
            
            upper = 0
            lower = 0
            if attrIndex.hasLowerBound():
                lower = attrIndex.getLower()
            if attrIndex.hasUpperBound():
                upper = attrIndex.getUpper()

            ## Check the attribute index xrange is valid
            ##
            if lower > upper or upper >= numComp:
                result = om.MPxSurfaceShape.kMatchInvalidAttributeRange

            else:
                path = item.getDagPath(0)
                fnComp = om.MFnSingleIndexedComponent()
                objComp = fnComp.create( typeComp )

                for i in range(lower, upper+1):
                    fnComp.addElement( i )
                
                list.add( (path, objComp), False )

        else:
            ## Pass this to the parent class
            result = om.MPxSurfaceShape.matchComponent(self, item, spec, list )

        return result

    def match(self, mask, componentList):
        ##
        ## Description:
        ##
        ##      Check for matches between selection type / component list, and
        ##      the type of this shape / or it's components
        ##
        ##      This is used by sets and deformers to make sure that the selected
        ##      components fall into the "vertex only" category.
        ##
        ## Arguments
        ##
        ##      mask          - selection type mask
        ##      componentList - possible component list
        ##
        ## Returns
        ##      True if matched any
        ##

        result = False

        if len(componentList) == 0:
            result = mask.intersects( om.MSelectionMask.kSelectMeshes )

        else:
            for comp in componentList:
                if comp.apiType() == om.MFn.kMeshVertComponent and mask.intersects(om.MSelectionMask.kSelectMeshVerts):
                    result = True
                    break

        return result

    ## Support deformers (components)
    ##
    def createFullVertexGroup(self):
        ##
        ## Description
        ##     This method is used by maya when it needs to create a component
        ##     containing every vertex (or control point) in the shape.
        ##     This will get called if you apply some deformer to the whole
        ##     shape, i.e. select the shape in object mode and add a deformer to it.
        ##
        ## Returns
        ##
        ##    A "complete" component representing all vertices in the shape.
        ##

        ## Create a vertex component
        ##
        fnComponent = om.MFnSingleIndexedComponent()
        fullComponent = fnComponent.create( om.MFn.kMeshVertComponent )

        ## Set the component to be complete, i.e. the elements in
        ## the component will be [0:numVertices-1]
        ##
        numVertices = len(self.meshGeom().vertices)
        fnComponent.setCompleteData( numVertices )

        return fullComponent

    def getShapeSelectionMask(self):
        ##
        ## Description
        ##     This method is overriden to support interactive object selection in Viewport 2.0
        ##
        ## Returns
        ##
        ##    The selection mask of the shape
        ##

        selType = om.MSelectionMask.kSelectMeshes
        return om.MSelectionMask( selType )

    def getComponentSelectionMask(self):
        ##
        ## Description
        ##     This method is overriden to support interactive component selection in Viewport 2.0
        ##
        ## Returns
        ##
        ##    The mask of the selectable components of the shape
        ##

        selMask = om.MSelectionMask(om.MSelectionMask.kSelectMeshVerts)
        selMask.addMask(om.MSelectionMask.kSelectMeshEdges)
        selMask.addMask(om.MSelectionMask.kSelectMeshFaces)
        return selMask

    def localShapeInAttr(self):
        ##
        ## Description
        ##
        ##    Returns the input attribute of the shape. This is used by
        ##    maya to establish input connections for deformers etc.
        ##    This attribute must be data of type kGeometryData.
        ##
        ## Returns
        ##
        ##    input attribute for the shape
        ##

        return apiMesh.inputSurface

    def localShapeOutAttr(self):
        ##
        ## Description
        ##
        ##    Returns the output attribute of the shape. This is used by
        ##    maya to establish out connections for deformers etc.
        ##    This attribute must be data of type kGeometryData.
        ##
        ## Returns
        ##
        ##    output attribute for the shape
        ##
        ##

        return apiMesh.outputSurface

    def worldShapeOutAttr(self):
        ##
        ## Description
        ##
        ##    Returns the output attribute of the shape. This is used by
        ##    maya to establish out connections for deformers etc.
        ##    This attribute must be data of type kGeometryData.
        ##
        ## Returns
        ##
        ##    output attribute for the shape
        ##
        ##

        return apiMesh.outputSurface

    def cachedShapeAttr(self):
        ##
        ## Description
        ##
        ##    Returns the cached shape attribute of the shape.
        ##    This attribute must be data of type kGeometryData.
        ##
        ## Returns
        ##
        ##    cached shape attribute
        ##

        return apiMesh.cachedSurface


    def geometryData(self):
        ##
        ## Description
        ##
        ##    Returns the data object for the surface. This gets
        ##    called internally for grouping (set) information.
        ##

        datablock = self.forceCache()
        handle = datablock.inputValue( apiMesh.inputSurface )
        return handle.data()

    def closestPoint(self, toThisPoint, theClosestPoint, tolerance):
        ##
        ## Description
        ##
        ##      Returns the closest point to the given point in space.
        ##      Used for rigid bind of skin.  Currently returns wrong results;
        ##      override it by implementing a closest point calculation.

        ## Iterate through the geometry to find the closest point within
        ## the given tolerance.
        ##
        geometry = self.meshGeom()
        numVertices = len(geometry.vertices)
        for i in range(numVertices):
            tryThisOne = geometry.vertices[i]

        ## Set the output point to the result (hardcode for debug just now)
        ##
        theClosestPoint = geometry.vertices[0]

    ## Support the translate/rotate/scale tool (components)
    ##
    def transformUsing(self, mat, componentList, cachingMode=om.MPxSurfaceShape.kNoPointCaching, pointCache=None):
        ##
        ## Description
        ##
        ##    Transforms the given components. This method is used by
        ##    the move, rotate, and scale tools in component mode.
        ##    The bounding box has to be updated here, so do the normals and
        ##    any other attributes that depend on vertex positions.
        ##
        ## Arguments
        ##    mat           - matrix to tranform the components by
        ##    componentList - list of components to be transformed,
        ##                    or an empty list to indicate the whole surface
        ##    cachingMode   - how to use the supplied pointCache (kSavePoints, kRestorePoints)
        ##    pointCache    - if non-None, save or restore points from this list base
        ##                    on the cachingMode
        ##

        geometry = self.meshGeom()

        ## Create cachingMode boolean values for clearer reading of conditional code below
        ##
        savePoints    = (cachingMode == om.MPxSurfaceShape.kSavePoints and pointCache is not None)
        restorePoints = (cachingMode == om.MPxSurfaceShape.kRestorePoints and pointCache is not None)

        cacheIndex = 0
        cacheLen = 0
        if pointCache:
            cacheLen = len(pointCache)

        if restorePoints:
            ## restore the points based on the data provided in the pointCache attribute
            ##
            if len(componentList) > 0:
                ## traverse the component list
                ##
                for comp in componentList:
                    fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                    elemCount = fnComp.elementCount

                    for idx in range(elementCount):
                        elemIndex = fnComp.element(idx)
                        geometry.vertices[elemIndex] = pointCache[cacheIndex]
                        cacheIndex += 1
                        if cacheIndex >= cacheLen:
                            break

                    if cacheIndex >= cacheLen:
                        break

            else:
                ## if the component list is of zero-length, it indicates that we
                ## should transform the entire surface
                ##
                vertLen = len(geometry.vertices)
                for idx in range(vertLen):
                    geometry.vertices[idx] = pointCache[cacheIndex]
                    cacheIndex += 1
                    if cacheIndex >= cacheLen:
                        break

        else:
            ## Transform the surface vertices with the matrix.
            ## If savePoints is True, save the points to the pointCache.
            ##
            if len(componentList) > 0:
                ## Traverse the componentList
                ##
                setSizeIncrement = True
                for comp in componentList:
                    fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                    elemCount = fnComp.elementCount

                    if savePoints and setSizeIncrement:
                        pointCache.sizeIncrement = elemCount
                        setSizeIncrement = False

                    for idx in range(elemCount):
                        elemIndex = fnComp.element(idx)
                        if savePoints:
                            pointCache.append(geometry.vertices[elemIndex])

                        geometry.vertices[elemIndex] *= mat
                        geometry.normals[idx] = geometry.normals[idx].transformAsNormal( mat )

            else:
                ## If the component list is of zero-length, it indicates that we
                ## should transform the entire surface
                ##
                vertLen = len(geometry.vertices)
                if savePoints:
                    pointCache.sizeIncrement = vertLen

                for idx in range(vertLen):
                    if savePoints:
                        pointCache.append(geometry.vertices[idx])

                    geometry.vertices[idx] *= mat
                    geometry.normals[idx] = geometry.normals[idx].transformAsNormal( mat )

        ## Update the surface
        self.updateCachedSurface( geometry, componentList )

    def tweakUsing(self, mat, componentList, cachingMode, pointCache, handle):
        ##
        ## Description
        ##
        ##    Transforms the given components. This method is used by
        ##    the move, rotate, and scale tools in component mode when the
        ##    tweaks for the shape are stored on a separate tweak node.
        ##    The bounding box has to be updated here, so do the normals and
        ##    any other attributes that depend on vertex positions.
        ##
        ## Arguments
        ##    mat           - matrix to tranform the components by
        ##    componentList - list of components to be transformed,
        ##                    or an empty list to indicate the whole surface
        ##    cachingMode   - how to use the supplied pointCache (kSavePoints, kRestorePoints, kUpdatePoints)
        ##    pointCache    - if non-null, save or restore points from this list base
        ##                    on the cachingMode
        ##    handle        - handle to the attribute on the tweak node where the
        ##                    tweaks should be stored
        ##

        geometry = self.meshGeom()

        ## Create cachingMode boolean values for clearer reading of conditional code below
        ##
        savePoints    = (cachingMode == om.MPxSurfaceShape.kSavePoints and pointCache is not None)
        updatePoints  = (cachingMode == om.MPxSurfaceShape.kUpdatePoints and pointCache is not None)
        restorePoints = (cachingMode == om.MPxSurfaceShape.kRestorePoints and pointCache is not None)

        builder = handle.builder()

        cacheIndex = 0
        cacheLen = 0
        if pointCache:
            cacheLen = len(pointCache)

        if restorePoints:
            ## restore points from the pointCache
            ##
            if len(componentList) > 0:
                ## traverse the component list
                ##
                for comp in componentList:
                    fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                    elemCount = fnComp.elementCount

                    for idx in range(elementCount):
                        elemIndex = fnComp.element(idx)
                        cachePt = pointCache[cacheIndex]
                        elem = builder.addElement( elemIndex )
                        elem.set3Double(cachePt.x, cachePt.y, cachePt.z)
                        cacheIndex += 1
                        if cacheIndex >= cacheLen:
                            break

                    if cacheIndex >= cacheLen:
                        break

            else:
                ## if the component list is of zero-length, it indicates that we
                ## should transform the entire surface
                ##
                vertLen = len(geometry.vertices)
                for idx in range(vertLen):
                    cachePt = pointCache[cacheIndex]
                    elem = builder.addElement( idx )
                    elem.set3Double(cachePt.x, cachePt.y, cachePt.z)
                    cacheIndex += 1
                    if cacheIndex >= cacheLen:
                        break

        else:
            ## Tweak the points. If savePoints is True, also save the tweaks in the
            ## pointCache. If updatePoints is True, add the new tweaks to the existing
            ## data in the pointCache.
            ##
            if len(componentList) > 0:
                setSizeIncrement = True
                for comp in componentList:
                    fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                    elemCount = fnComp.elementCount

                    if savePoints and setSizeIncrement:
                        pointCache.sizeIncrement = elemCount
                        setSizeIncrement = False

                    for idx in range(elementCount):
                        elemIndex = fnComp.element(idx)
                        currPt = newPt = geometry.vertices[elemIndex]
                        newPt *= mat
                        delta = newPt - currPt
                        elem = builder.addElement( elemIndex )
                        elem.set3Double(delta.x, delta.y, delta.z)

                        if savePoints:
                            ## store the points in the pointCache for undo
                            ##
                            pointCache.append(delta*(-1.0))

                        elif updatePoints and cacheIndex < cacheLen:
                            pointCache[cacheIndex] = pointCache[cacheIndex] - delta
                            cacheIndex += 1

            else:
                ## if the component list is of zero-length, it indicates that we
                ## should transform the entire surface
                ##
                vertLen = len(geometry.vertices)
                if savePoints:
                    pointCache.sizeIncrement = vertLen

                for idx in range(vertLen):
                    currPt = newPt = geometry.vertices[idx]
                    newPt *= mat
                    delta = newPt - currPt
                    elem = builder.addElement( idx )
                    elem.set3Double(delta.x, delta.y, delta.z)

                    if savePoints:
                        ## store the points in the pointCache for undo
                        ##
                        pointCache.append(delta*(-1.0))

                    elif updatePoints and idx < cacheLen:
                        pointCache[cacheIndex] = pointCache[cacheIndex] - delta
                        cacheIndex += 1

        ## Set the builder into the handle.
        ##
        handle.set(builder)

        ## Tell maya the bounding box for this object has changed
        ## and thus "boundingBox()" needs to be called.
        ##
        self.childChanged( om.MPxSurfaceShape.kBoundingBoxChanged )

        ## Signal to the viewport that it needs to update the object
        self.signalDirtyToViewport()

    ## Support the soft-select translate/rotate/scale tool (components)
    ##
    def weightedTransformUsing(self, xform, space, componentList, cachingMode, pointCache, freezePlane):
        ##
        ## Description
        ##
        ##    Transforms the given soft-selected components interpolated using the specified weights.
        ##    This method is used by the move, rotate, and scale tools in component mode.
        ##    The bounding box has to be updated here, so do the normals and
        ##    any other attributes that depend on vertex positions.
        ##    It is similar to the transformUsing() virtual function.
        ##
        ## Arguments
        ##
        ##    xform           the matrix representing the transformation that is to be applied to the components
        ##    space           the matrix representing the transformation space to perform the interpolated transformation.
        ##                    A value of None indicates it should be ignored.
        ##    componentList   a list of components to be transformed and their weights.  This list will not be empty.
        ##    cachingMode     whether the points should be added/updated in the pointCache, or restored from
        ##                    the pointCache, or transform using the original values in the pointCache.
        ##    pointCache      used to store for undo and restore points during undo
        ##    freezePlane     used for symmetric transformation of components.  A value of None indicates
        ##                    it is not used and there is no symmetric transformation.
        ##

        ## For example purposes only, use the default MPxSurfaceShape.weightedTransformUsing() if the
        ## useWeightedTransformUsingFunction is False
        ##
        plg_useWeightedTransformUsingFunction = om.MPlug( self.thisMObject(), apiMesh.useWeightedTransformUsingFunction )
        val_useWeightedTransformUsingFunction = plg_useWeightedTransformUsingFunction.asBool()
        if not val_useWeightedTransformUsingFunction:
            om.MPxSurfaceShape.weightedTransformUsing(self, xform, space, componentList, cachingMode, pointCache, freezePlane)
            self.signalDirtyToViewport()
            return

        ## Create cachingMode boolean values for clearer reading of conditional code below
        ##
        savePoints          = (cachingMode == om.MPxSurfaceShape.kSavePoints and pointCache is not None)
        updatePoints        = (cachingMode == om.MPxSurfaceShape.kUpdatePoints and pointCache is not None)
        restorePoints       = (cachingMode == om.MPxSurfaceShape.kRestorePoints and pointCache is not None)
        transformOrigPoints = (cachingMode == om.MPxSurfaceShape.kTransformOriginalPoints and pointCache is not None)

        ## Pre-calculate parameters
        spaceInv = om.MMatrix()
        if space:
            spaceInv = space.inverse()

        ## Traverse the componentList and modify the control points
        ##
        geometry = self.meshGeom()
        almostZero = 1.0e-5 ## Hardcoded tolerance
        pointCacheIndex = 0
        setSizeIncrement = True

        for comp in componentList:
            fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
            elemCount = fnComp.elementCount
            hasWeights = fnComp.hasWeights
            hasSeam = (freezePlane is not None)

            if savePoints and setSizeIncrement:
                pointCache.sizeIncrement = elemCount
                setSizeIncrement = False

            for idx in range(elementCount):
                elemIndex = fnComp.element( idx )
                perc = 1.0
                if hasWeights:
                    perc = fnComp.weight(idx).influence()   ## get the weight for the component

                ## Only act upon points (store in pointCache, transform, etc) that have a non-zero weight
                if perc > almostZero:   ## if the point has enough weight to be transformed
                    if restorePoints:
                        ## restore the original point from the point cache
                        geometry.vertices[elemIndex] = om.MVector( pointCache[pointCacheIndex] )
                        pointCacheIndex += 1

                    else:   ## perform point transformation
                        ## Update the pointCache with the original value
                        if savePoints:
                            pointCache.append( geometry.vertices[elemIndex] )

                        elif transformOrigPoints:   ## start by reverting points back to their original values stored in the pointCache for the transformation
                            geometry.vertices[elemIndex] = om.MVector( pointCache[pointCacheIndex] )

                        elif updatePoints:  ## update the pointCache with the current values
                            pointCache[pointCacheIndex] = geometry.vertices[elemIndex]

                        ## Compute interpolated transformation matrix
                        mat = om.MMatrix()
                        if perc == 1.0:
                            mat = xform.asMatrix()
                        elif space:
                            mat = space * xform.asMatrix(perc) * spaceInv
                        else:
                            mat = xform.asMatrix(perc)

                        ## transform to new position
                        currPt = newPt = geometry.vertices[elemIndex]
                        newPt *= mat

                        ## handle symmetry and reflection
                        if hasSeam and fnComp.weight(idx).seam() > 0.0:
                            newPt += freezePlane.normal() * (fnComp.weight(idx).seam() * (freezePlane.directedDistance(currPt) - freezePlane.directedDistance(newPt)))

                        ## Update the geometry with the new point
                        geometry.vertices[elemIndex] = newPt
                        pointCacheIndex += 1

        ## Update the surface
        self.updateCachedSurface( geometry, componentList )

    def weightedTweakUsing(self, xform, space, componentList, cachingMode, pointCache, freezePlane, handle):
        ##
        ## Description
        ##
        ##    Transforms the given soft-selected components interpolated using the specified weights.
        ##    This method is used by the move, rotate, and scale tools in component mode when the
        ##    tweaks for the shape are stored on a separate tweak node.
        ##    The bounding box has to be updated here, so do the normals and
        ##    any other attributes that depend on vertex positions.
        ##
        ##    It is similar to the tweakUsing() virtual function and is based on apiMesh.tweakUsing().
        ##
        ##
        ## Arguments
        ##
        ##    xform           the matrix representing the transformation that is to be applied to the components
        ##    space           the matrix representing the transformation space to perform the interpolated transformation.
        ##                    A value of None indicates it should be ignored.
        ##    componentList   a list of components to be transformed and their weights.  This list will not be empty.
        ##    cachingMode     whether the points should be added/updated in the pointCache, or restored from
        ##                    the pointCache, or transform using use the original values in the pointCache.
        ##    pointCache      used to store for undo and restore points during undo
        ##    freezePlane     used for symmetric transformation of components.  A value of None indicates
        ##                    it is not used and there is no symmetric transformation.
        ##    handle          handle to the attribute on the tweak node where the
        ##                    tweaks should be stored
        ##
    
        ## For example purposes only, use the default MPxSurfaceShape.weightedTweakUsing() if the
        ## useWeightedTweakUsingFunction is False
        ##
        plg_useWeightedTweakUsingFunction = om.MPlug( self.thisMObject(), apiMesh.useWeightedTweakUsingFunction )
        val_useWeightedTweakUsingFunction = plg_useWeightedTweakUsingFunction.asBool()
        if not val_useWeightedTweakUsingFunction:
            om.MPxSurfaceShape.weightedTweakUsing(self, xform, space, componentList, cachingMode, pointCache, freezePlane, handle)
            return

        geometry = self.meshGeom()

        ## Create cachingMode boolean values for clearer reading of conditional code below
        ##
        savePoints          = (cachingMode == om.MPxSurfaceShape.kSavePoints and pointCache is not None)
        updatePoints        = (cachingMode == om.MPxSurfaceShape.kUpdatePoints and pointCache is not None)
        restorePoints       = (cachingMode == om.MPxSurfaceShape.kRestorePoints and pointCache is not None)
        transformOrigPoints = (cachingMode == om.MPxSurfaceShape.kTransformOriginalPoints and pointCache is not None)

        builder = handle.builder()

        cacheIndex = 0
        cacheLen = 0
        if pointCache:
            cacheLen = len(pointCache)

        if restorePoints:
            ## restore points from the pointCache
            ##
            ## traverse the component list
            ##
            for comp in componentList:
                fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                elemCount = fnComp.elementCount

                for idx in range(elementCount):
                    elemIndex = fnComp.element( idx )
                    cachePt = pointCache[cacheIndex]
                    elem = builder.addElement( elemIndex )
                    elem.set3Double(cachePt.x, cachePt.y, cachePt.z)
                    cacheIndex += 1
                    if cacheIndex >= cacheLen:
                        break

        else:
            ## Tweak the points. If savePoints is True, also save the tweaks in the
            ## pointCache. If updatePoints is True, add the new tweaks to the existing
            ## data in the pointCache.
            ##

            ## Specify a few parameters (for weighted transformation)
            almostZero = 1.0e-5 ## Hardcoded tolerance
            setSizeIncrement = True
            spaceInv = om.MMatrix()
            if space:
                spaceInv = space.inverse()

            for comp in componentList:
                fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                elemCount = fnComp.elementCount
                hasWeights = fnComp.hasWeights ## (for weighted transformation)
                hasSeam = (freezePlane is not None)  ## (for weighted transformation)

                if savePoints and setSizeIncrement:
                    pointCache.sizeIncrement = elemCount
                    setSizeIncrement = False

                for idx in range(elementCount):
                    elemIndex = fnComp.element( idx )
                    perc = 1.0
                    if hasWeights:
                        perc = fnComp.weight(idx).influence()   ## get the weight for the component

                    ## Only act upon points (store in pointCache, transform, etc) that have a non-zero weight
                    if perc > almostZero:   ## if the point has enough weight to be transformed (for weighted transformation)

                        ## Compute interpolated transformation matrix (for weighted transformation)
                        ##
                        mat = om.MMatrix()
                        if perc == 1.0:
                            mat = xform.asMatrix()
                        elif space:
                            mat = space * xform.asMatrix(perc) * spaceInv
                        else:
                            mat = xform.asMatrix(perc)

                        ## Start by reverting points back to their original values stored in
                        ## the pointCache for the transformation
                        ##
                        if transformOrigPoints:
                            geometry.vertices[elemIndex] = om.MVector( pointCache[cacheIndex] )

                        ## Perform transformation of the point
                        ##
                        currPt = newPt = geometry.vertices[elemIndex]
                        newPt *= mat

                        ## Handle symmetry and reflection (for weighted transformation)
                        ##
                        if hasSeam and fnComp.weight(idx).seam() > 0.0:
                            newPt += freezePlane.normal() * (fnComp.weight(idx).seam() * (freezePlane.directedDistance(currPt) - freezePlane.directedDistance(newPt)))

                        ## Calculate deltas and final positions
                        delta = newPt - currPt

                        elem = builder.addElement( elemIndex )
                        elem.set3Double(delta.x, delta.y, delta.z)

                        if savePoints:
                            ## store the points in the pointCache for undo
                            ##
                            pointCache.append(delta*(-1.0))
                        elif updatePoints and cacheIndex < cacheLen:
                            pointCache[cacheIndex] = pointCache[cacheIndex] - delta
                            cacheIndex += 1

        ## Set the builder into the handle.
        ##
        handle.set(builder)

        ## Tell maya the bounding box for this object has changed
        ## and thus "boundingBox()" needs to be called.
        ##
        self.childChanged( om.MPxSurfaceShape.kBoundingBoxChanged )

    ## Support the move tools normal/u/v mode (components)
    ##
    def vertexOffsetDirection(self, component, direction, mode, normalize):
        ##
        ## Description
        ##
        ##    Returns offsets for the given components to be used my the
        ##    move tool in normal/u/v mode.
        ##
        ## Arguments
        ##
        ##    component - components to calculate offsets for
        ##    direction - array of offsets to be filled
        ##    mode      - the type of offset to be calculated
        ##    normalize - specifies whether the offsets should be normalized
        ##
        ## Returns
        ##
        ##    True if the offsets could be calculated, False otherwise
        ##

        fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(component) )
        if component.apiType() != om.MFn.kMeshVertComponent:
            return False

        geometry = self.meshGeom()
        if not geometry:
            return False

        ## For each vertex add the appropriate offset
        ##
        for idx in fnComp:
            normal = geometry.normals[ idx ]

            if mode == om.MPxSurfaceShape.kNormal:
                if normalize:
                    normal.normalize()
                direction.append( normal )

            else:
                ## Construct an orthonormal basis from the normal
                ## uAxis, and vAxis are the new vectors.
                ##
                normal.normalize()

                i = 0
                a = math.abs(normal[0])

                if a < math.abs(normal[1]):
                    i = 1
                    a = fabs(normal[1])

                if a < math.abs(normal[2]):
                    i = 2

                j = (i+1)%3
                k = (j+1)%3

                a = math.sqrt(normal[i]*normal[i] + normal[j]*normal[j])
                uAxis[i] = -normal[j]/a
                uAxis[j] =  normal[i]/a
                uAxis[k] = 0.0
                vAxis = normal^uAxis

                if mode == om.MPxSurfaceShape.kUTangent or mode == om.MPxSurfaceShape.kUVNTriad:
                    if normalize:
                        uAxis.normalize()
                    direction.append( uAxis )

                if mode == om.MPxSurfaceShape.kVTangent or mode == om.MPxSurfaceShape.kUVNTriad:
                    if normalize:
                        vAxis.normalize()
                    direction.append( vAxis )

                if mode == om.MPxSurfaceShape.kUVNTriad:
                    if normalize:
                        normal.normalize()
                    direction.append( normal )

        return True

    ## Bounding box methods
    ##
    def isBounded(self):
        ##
        ## Description
        ##
        ##    Specifies that this object has a boundingBox.
        ##

        return True

    def boundingBox(self):
        ##
        ## Description
        ##
        ##    Returns the bounding box for this object.
        ##    It is a good idea not to recompute here as this funcion is called often.
        ##
        if self.fShapeDirty:
            # Update:
            self.meshObject()

        thisNode = self.thisMObject()
        c1Plug = om.MPlug( thisNode, apiMesh.bboxCorner1 )
        c2Plug = om.MPlug( thisNode, apiMesh.bboxCorner2 )
        corner1Object = c1Plug.asMObject()
        corner2Object = c2Plug.asMObject()

        fnData = om.MFnNumericData()
        fnData.setObject( corner1Object )
        corner1 = fnData.getData()

        fnData.setObject( corner2Object )
        corner2 = fnData.getData()

        corner1Point = om.MPoint( corner1[0], corner1[1], corner1[2] )
        corner2Point = om.MPoint( corner2[0], corner2[1], corner2[2] )

        return om.MBoundingBox( corner1Point, corner2Point )

    ## Associates a user defined iterator with the shape (components)
    ##
    def geometryIteratorSetup(self, componentList, components, forReadOnly=False):
        ##
        ## Description
        ##
        ##    Creates a geometry iterator compatible with his shape.
        ##
        ## Arguments
        ##
        ##    componentList - list of components to be iterated
        ##    components    - component to be iterator
        ##    forReadOnly   -
        ##
        ## Returns
        ##
        ##    An iterator for the components
        ##

        if components.isNull():
            vtxComponents = om.MObjectArray([self.convertToVertexComponent(c) for c in componentList])
            return apiMeshGeomIterator( self.meshGeom(), vtxComponents )

        return apiMeshGeomIterator( self.meshGeom(), self.convertToVertexComponent(components) )

    def acceptsGeometryIterator(self, arg0, arg1=None, arg2=None):
        ##
        ## Description
        ##
        ##    Specifies that this shape can provide an iterator for getting/setting
        ##    control point values.
        ##
        ## Arguments
        ##
        ##    writable   - maya asks for an iterator that can set points if this is True
        ##
        ## OR
        ##
        ##    component   - the component
        ##    writable    - maya asks for an iterator that can set points if this is True
        ##    forReadOnly - maya asking for an iterator for querying only
        ##

        return True

    ##########################################################
    ##
    ## Helper methods
    ##
    ##########################################################

    def hasHistory(self):
        ##
        ## Description
        ##
        ##    Returns True if the shape has input history, False otherwise.
        ##
        return self.fHasHistoryOnCreate

    def shapeDirty(self):
        ##
        ## Description
        ##
        ##    Returns True if the input surface of the shape has been dirtied since
        ##    the last reset of the flag
        ##
        return self.fShapeDirty

    def resetShapeDirty(self):
        ##
        ## Description
        ##
        ##    Reset the shape dirty state of the node
        ##
        self.fShapeDirty = False

    def materialDirty(self):
        ##
        ## Description
        ##
        ##    Returns true if the shading group of the shape has been changed since
        ##    the last reset of the flag
        ##
        return self.fMaterialDirty

    def setMaterialDirty(self, dirty):
        ##
        ## Description
        ##
        ##    Reset the material dirty state of the node
        ##
        self.fMaterialDirty = dirty

    def computeInputSurface(self, plug, datablock):
        ##
        ## Description
        ##
        ##    If there is input history, evaluate the input attribute
        ##

        ## Get the input surface if there is history
        ##
        if self.hasHistory():
            inputHandle = datablock.inputValue( apiMesh.inputSurface )

            surf = inputHandle.asPluginData()
            if not isinstance(surf, apiMeshData):
                raise RuntimeError("computeInputSurface : invalid inputSurface data found")

            ## Create the cachedSurface and copy the input surface into it
            ##
            fnDataCreator = om.MFnPluginData()
            fnDataCreator.create( apiMeshData.id )

            newCachedData = fnDataCreator.data()
            if not isinstance(newCachedData, apiMeshData):
                raise RuntimeError("computeInputSurface : invalid proxy cached apiMeshData object")

            newCachedData.fGeometry.copy(surf.fGeometry)

            cachedHandle = datablock.outputValue( apiMesh.cachedSurface )
            if not isinstance(cachedHandle, om.MDataHandle):
                raise RuntimeError("computeInputSurface : invalid cachedSurface")

            cachedHandle.setMPxData( newCachedData )

    def computeOutputSurface(self, plug, datablock):
        ##
        ## Description
        ##
        ##    Compute the outputSurface attribute.
        ##
        ##    If there is no history, use cachedSurface as the
        ##    input surface. All tweaks will get written directly
        ##    to it. Output is just a copy of the cached surface
        ##    that can be connected etc.
        ##

        ## Check for an input surface. The input surface, if it
        ## exists, is copied to the cached surface.
        ##
        self.computeInputSurface( plug, datablock )

        ## Get a handle to the cached data
        ##
        cachedHandle = datablock.outputValue( apiMesh.cachedSurface )
        if not isinstance(cachedHandle, om.MDataHandle):
            raise RuntimeError("computeOutputSurface : invalid cachedSurface")

        cached = cachedHandle.asPluginData()
        if not isinstance(cached, apiMeshData):
            raise RuntimeError("computeOutputSurface : invalid cachedSurface data found")

        datablock.setClean( plug )

        ## Apply any vertex offsets.
        ##
        if self.hasHistory():
            self.applyTweaks( datablock, cached.fGeometry )

        else:
            cpHandle = datablock.inputArrayValue( om.MPxSurfaceShape.mControlPoints )
            cpHandle.setAllClean()

        ## Create some output data
        ##
        fnDataCreator = om.MFnPluginData()
        fnDataCreator.create( apiMeshData.id )

        newData = fnDataCreator.data()
        if not isinstance(newData, apiMeshData):
            raise RuntimeError("computeOutputSurface : invalid proxy cached apiMeshData object")

        ## Copy the data
        ##
        newData.fGeometry.copy(cached.fGeometry)

        ## Assign the new data to the outputSurface handle
        ##
        outHandle = datablock.outputValue( apiMesh.outputSurface )
        outHandle.setMPxData( newData )

        ## Update the bounding box attributes
        ##
        self.computeBoundingBox( datablock )

        # The plug was computed successfully
        return self

    def computeWorldSurface(self, plug, datablock):
        ##
        ## Description
        ##
        ##    Compute the worldSurface attribute.
        ##

        self.computeOutputSurface( plug, datablock )
        inHandle = datablock.outputValue( apiMesh.outputSurface )
        outSurf = inHandle.asPluginData()
        if not isinstance(outSurf, apiMeshData):
            raise RuntimeError("computeWorldSurface : invalid outSurf")

        ## Create some output data
        ##
        fnDataCreator = om.MFnPluginData()
        fnDataCreator.create( apiMeshData.id )

        newData = fnDataCreator.data()
        if not isinstance(newData, apiMeshData):
            raise RuntimeError("computeWorldSurface : invalid proxy cached apiMeshData object")

        ## Get worldMatrix from MPxSurfaceShape and set it to MPxGeometryData
        worldMat = self.getWorldMatrix(datablock, 0)
        newData.matrix = worldMat

        ## Copy the data
        ##
        newData.fGeometry.copy( outSurf.fGeometry )

        ## Assign the new data to the outputSurface handle
        ##
        arrayIndex = plug.logicalIndex()

        worldHandle = datablock.outputArrayValue( apiMesh.worldSurface )
        builder = worldHandle.builder()
        outHandle = builder.addElement( arrayIndex )

        outHandle.setMPxData( newData )

        # The plug was computed successfully
        return self

    def computeBoundingBox(self, datablock):
        ##
        ## Description
        ##
        ##    Use the larges/smallest vertex positions to set the corners
        ##    of the bounding box.
        ##

        ## Update bounding box
        ##
        lowerHandle = datablock.outputValue( apiMesh.bboxCorner1 )
        upperHandle = datablock.outputValue( apiMesh.bboxCorner2 )

        geometry = self.meshGeom()
        cnt = len(geometry.vertices)
        if cnt == 0:
            return

        ## This clears any old bbox values
        ##
        tmppnt = geometry.vertices[0]
        lower = [ tmppnt[0], tmppnt[1], tmppnt[2] ]
        upper = [ tmppnt[0], tmppnt[1], tmppnt[2] ]

        for i in range(cnt):
            pnt = geometry.vertices[i]

            if pnt[0] < lower[0]:   lower[0] = pnt[0]
            if pnt[1] < lower[1]:   lower[1] = pnt[1]
            if pnt[2] < lower[2]:   lower[2] = pnt[2]

            if pnt[0] > upper[0]:   upper[0] = pnt[0]
            if pnt[1] > upper[1]:   upper[1] = pnt[1]
            if pnt[2] > upper[2]:   upper[2] = pnt[2]

        lowerHandle.set3Double(lower[0], lower[1], lower[2])
        upperHandle.set3Double(upper[0], upper[1], upper[2])

        lowerHandle.setClean()
        upperHandle.setClean()

        ## Signal that the bounding box has changed.
        ##
        self.childChanged( om.MPxSurfaceShape.kBoundingBoxChanged )
        
    def convertToVertexComponent(self, components):
        """
            Converts edge and face components into vertex components. This
            allows applying transform offsets to the vertex when edge or faces
            are selected.
        """
        retVal = components

        try:
            srcComponent = om.MFnSingleIndexedComponent(components)
            srcComponentType = srcComponent.componentType
        except:
            return components
        
        if srcComponentType != om.MFn.kMeshVertComponent:
            srcIndices = set(srcComponent.getElements())
            retVal = srcComponent.create(om.MFn.kMeshVertComponent)
            vtxComponent = om.MFnSingleIndexedComponent(retVal)
            
            geomPtr = self.meshGeom()
            
            base = 0
            edgeId = 0
            for faceIdx in range(0, geomPtr.faceCount):
                # ignore degenerate faces
                numVerts = geomPtr.face_counts[faceIdx]
                if numVerts > 2:
                    for v in range(0, numVerts):
                        if srcComponentType == om.MFn.kMeshEdgeComponent:
                            if edgeId in srcIndices:
                                vindex1 = base + (v % numVerts)
                                vindex2 = base + ((v+1) % numVerts)

                                vertexId1 = geomPtr.face_connects[vindex1]
                                vertexId2 = geomPtr.face_connects[vindex2]

                                vtxComponent.addElement(vertexId1)
                                vtxComponent.addElement(vertexId2)

                            edgeId += 1
                        else:
                            # Face component:
                            if faceIdx in srcIndices:
                                vindex = base + (v % numVerts)
                                vertexId = geomPtr.face_connects[vindex]
                                vtxComponent.addElement(vertexId)

                    base += numVerts

        return retVal

    def applyTweaks(self, datablock, geometry):
        ##
        ## Description
        ##
        ##    If the shape has history, apply any tweaks (offsets) made
        ##    to the control points.
        ##

        cpHandle = datablock.inputArrayValue( om.MPxSurfaceShape.mControlPoints )

        ## Loop through the component list and transform each vertex.
        ##
        while not cpHandle.isDone():
            elemIndex = cpHandle.elementLogicalIndex()
            pntHandle = cpHandle.outputValue()

            offset = pntHandle.asDouble3()

            ## Apply the tweaks to the output surface
            ##
            geometry.vertices[elemIndex] += om.MPoint(offset[0],offset[1],offset[2])

            next(cpHandle)


    def updateCachedSurface(self, geometry, componentList):
        ##
        ## Description
        ##
        ##    Update the cached surface attribute, handle the tweak history as appropriate,
        ##    and trigger a bounding box change calculation.
        ##
        ## Arguments
        ##    geometry       - the modified geometry to apply to the cached surface attribute
        ##

        ## Retrieve the value of the cached surface attribute.
        ## We will set the new geometry data into the cached surface attribute
        ##
        ## Access the datablock directly. This code has to be efficient
        ## and so we bypass the compute mechanism completely.
        ## NOTE: In general we should always go though compute for getting
        ## and setting attributes.
        ##
        datablock = self.forceCache()

        cachedHandle = datablock.outputValue( apiMesh.cachedSurface )
        cached = cachedHandle.asPluginData()

        dHandle = datablock.outputValue( om.MPxSurfaceShape.mControlPoints )

        ## If there is history then calculate the tweaks necessary for
        ## setting the final positions of the vertices.
        ##
        if self.hasHistory() and cached:
            ## Since the shape has history, we need to store the tweaks (deltas)
            ## between the input shape and the tweaked shape in the control points
            ## attribute.
            ##
            self.buildControlPoints( datablock, len(geometry.vertices) )

            cpHandle = om.MArrayDataHandle( dHandle )

            ## Loop through the component list and transform each vertex.
            ##
            for comp in componentList:
                fnComp = om.MFnSingleIndexedComponent( self.convertToVertexComponent(comp) )
                for elemIndex in fnComp.getElements():
                    cpHandle.jumpToLogicalElement( elemIndex )
                    pntHandle = cpHandle.outputValue()

                    pnt = pntHandle.asDouble3()

                    oldPnt = cached.fGeometry.vertices[elemIndex]
                    newPnt = geometry.vertices[elemIndex]
                    offset = newPnt - oldPnt

                    pnt[0] += offset[0]
                    pnt[1] += offset[1]
                    pnt[2] += offset[2]

                    pntHandle.set3Double(pnt[0], pnt[1], pnt[2])

        ## Copy outputSurface to cachedSurface
        ##
        if cached:
            cached.fGeometry.copy(geometry)

        pCPs = om.MPlug( self.thisMObject(), om.MPxSurfaceShape.mControlPoints)
        pCPs.setMDataHandle(dHandle)

        ## Moving vertices will likely change the bounding box.
        ##
        self.computeBoundingBox( datablock )

        ## Tell maya the bounding box for this object has changed
        ## and thus "boundingBox()" needs to be called.
        ##
        self.childChanged( om.MPxSurfaceShape.kBoundingBoxChanged )

        ## Signal to the viewport that it needs to update the object
        self.signalDirtyToViewport()

    def getPointValue(self, pntInd):
        ##
        ## Description
        ##
        ##    Helper function to return the value of a given vertex
        ##    from the cachedMesh.
        ##
        geometry = self.cachedGeom()
        if geometry:
            return geometry.vertices[ pntInd ]

        return om.MPoint()

    def getChannelValue(self, pntInd, vlInd):
        ##
        ## Description
        ##
        ##    Helper function to return the value of a given vertex
        ##    from the cachedMesh.
        ##
        geometry = self.cachedGeom()
        if geometry:
            return geometry.vertices[ pntInd ][ vlInd ]

        return 0

    def setPointValue(self, pntInd, val):
        ##
        ## Description
        ##
        ##    Helper function to set the value of a given vertex
        ##    in the cachedMesh.
        ##
        geometry = self.cachedGeom()
        if geometry:
            geometry.vertices[ pntInd ] = om.MPoint(val)
    
        self.verticesUpdated()

    def setChannelValue(self, pntInd, vlInd, val):
        ##
        ## Description
        ##
        ##    Helper function to set the value of a given vertex
        ##    in the cachedMesh.
        ##
        geometry = self.cachedGeom()
        if geometry:
            geometry.vertices[ pntInd ][ vlInd ] = val
    
        self.verticesUpdated()

    def meshObject(self):
        ##
        ## Description
        ##
        ##    Get a reference to the mesh data (outputSurface)
        ##    from the datablock. If dirty then an evaluation is
        ##    triggered.
        ##

        ## Get the datablock for this node
        ##
        datablock = self.forceCache()

        ## Calling inputValue will force a recompute if the
        ## connection is dirty. This means the most up-to-date
        ## mesh data will be returned by this method.
        ##
        handle = datablock.inputValue( apiMesh.outputSurface )
        return handle.data()

    def meshGeom(self):
        ##
        ## Description
        ##
        ##    Returns the apiMeshGeom of the outputSurface.
        ##
        meshObj = self.meshObject()

        fnData = om.MFnPluginData( meshObj )
        data = fnData.data()
        if not isinstance(data, apiMeshData):
            raise RuntimeError("meshGeom : failed to get apiMeshData")
        return data.fGeometry

    def cachedObject(self):
        ##
        ## Description
        ##
        ##    Get a reference to the mesh data (cachedSurface)
        ##    from the datablock. No evaluation is triggered.
        ##

        ## Get the datablock for this node
        ##
        datablock = self.forceCache()
        handle = datablock.outputValue( apiMesh.cachedSurface )
        return handle.data()

    def cachedGeom(self):
        ##
        ## Description
        ##
        ##    Returns the apiMeshGeom of the cachedSurface.
        ##

        fnData = om.MFnPluginData( self.cachedObject() )
        data = fnData.data()
        if not isinstance(data, apiMeshData):
            raise RuntimeError("cachedGeom : failed to get apiMeshData")

        return data.fGeometry

    def buildControlPoints(self, datablock, count):
        ##
        ## Description
        ##
        ##    Check the controlPoints array. If there is input history
        ##    then we will use this array to store tweaks (vertex movements).
        ##

        cpH = datablock.outputArrayValue( om.MPxSurfaceShape.mControlPoints )

        oldBuilder = cpH.builder()
        if count != len(oldBuilder):
            ## Make and set the new builder based on the
            ## info from the old builder.
            builder = om.MArrayDataBuilder( oldBuilder )

            for vtx in range(count):
                builder.addElement( vtx )

            cpH.set( builder )

        cpH.setAllClean()

    def verticesUpdated(self):
        ##
        ## Description
        ##
        ##    Helper function to tell maya that this shape's
        ##    vertices have updated and that the bbox needs
        ##    to be recalculated and the shape redrawn.
        ##
        self.childChanged( om.MPxSurfaceShape.kBoundingBoxChanged )
        self.childChanged( om.MPxSurfaceShape.kObjectChanged )

    def setShapeDirty(self):
        self.fShapeDirty = True

    def notifyViewport(self):
        omr.MRenderer.setGeometryDrawDirty(self.thisMObject())

    def signalDirtyToViewport(self):
        self.setShapeDirty()
        self.notifyViewport()

class apiMeshGeometryShape(apiMesh):
    sDrawDbClassification = "drawdb/geometry/apiMesh_py"

    id = om.MTypeId(0x8009B)

    def __init__(self):
        super(apiMeshGeometryShape, self).__init__()
    
    @staticmethod
    def creator():
        return apiMeshGeometryShape()
    
    @staticmethod
    def initialize():
        return apiMesh.initialize()
    
class apiMeshSubsceneShape(apiMesh):
    sDrawDbClassification = "drawdb/subscene/apiMesh_py"

    id = om.MTypeId(0x8009C)
    
    def __init__(self):
        super(apiMeshSubsceneShape, self).__init__()
    
    @staticmethod
    def creator():
        return apiMeshSubsceneShape()
    
    @staticmethod
    def initialize():
        om.MPxNode.inheritAttributesFrom(apiMesh.sNodeName)
        return True


################################################################################
##
## apiMeshShapeUI
##
## Encapsulates the UI portion of a user defined shape. All of the
## drawing and selection code goes here.
##
################################################################################
class apiMeshUI(omui.MPxSurfaceShapeUI):

    @staticmethod
    def creator():
        return apiMeshUI()

    def __init__(self):
        omui.MPxSurfaceShapeUI.__init__(self)

    #####################################################################
    ##
    ## Overrides
    ##
    #####################################################################

    ## Main draw routine for UV editor. This is called by maya when the 
    ## shape is selected and the UV texture window is visible. 
    ## 
    def drawUV(self, view, info):
        ## 
        ## Description: 
        ##   Main entry point for UV drawing. This method is called by the UV 
        ##   texture editor when the shape is 'active'. 
        ## 
        ## Input: 
        ##   A 3dView. 
        ##

        meshNode = self.surfaceShape()
        geom = meshNode.meshGeom()

        if geom.uvcoords.uvcount() > 0:
            view.setDrawColor( om.MColor( (1.0, 0.0, 0.0) ) )
        
            if info.drawingFunction == omui.MTextureEditorDrawInfo.kDrawWireframe: 
                self.drawUVWireframe( geom, view, info )

            elif info.drawingFunction == omui.MTextureEditorDrawInfo.kDrawEverything or info.drawingFunction == omui.MTextureEditorDrawInfo.kDrawUVForSelect:
                self.drawUVWireframe( geom, view, info ) 
                self.drawUVMapCoordNum( geom, view, info, True )

            else:
                self.drawUVWireframe( geom, view, info )

    def canDrawUV(self):
        ##
        ## Description: 
        ##  Tells Maya that this surface shape supports uv drawing. 
        ##

        meshNode = self.surfaceShape()
        geom = meshNode.meshGeom()
        return (geom.uvcoords.uvcount() > 0)

    ## Main selection routine
    ##
    def select(self, selectInfo, selectionList, worldSpaceSelectPts):
        ##
        ## Description:
        ##
        ##     Main selection routine
        ##
        ## Arguments:
        ##
        ##     selectInfo           - the selection state information
        ##     selectionList        - the list of selected items to add to
        ##     worldSpaceSelectPts  -
        ##

        selected = False
        componentSelected = False
        hilited = False

        hilited = (selectInfo.displayStatus() == omui.M3dView.kHilite)
        if hilited:
            componentSelected = self.selectVertices( selectInfo, selectionList, worldSpaceSelectPts )
            selected = selected or componentSelected

        if not selected:
            meshNode = self.surfaceShape()

            ## NOTE: If the geometry has an intersect routine it should
            ## be called here with the selection ray to determine if the
            ## the object was selected.

            selected = True
            priorityMask = om.MSelectionMask( om.MSelectionMask.kSelectNurbsSurfaces )

            item = om.MSelectionList()
            item.add( selectInfo.selectPath() )

            xformedPt = om.MPoint()
            if selectInfo.singleSelection():
                center = meshNode.boundingBox().center
                xformedPt = center
                xformedPt *= selectInfo.selectPath().inclusiveMatrix()

            selectInfo.addSelection( item, xformedPt, selectionList, worldSpaceSelectPts, priorityMask, False )

        return selected

    #####################################################################
    ##
    ## Helper routines
    ##
    #####################################################################

    def selectVertices(self, selectInfo, selectionList, worldSpaceSelectPts):
        ##
        ## Description:
        ##
        ##     Vertex selection.
        ##
        ## Arguments:
        ##
        ##     selectInfo           - the selection state information
        ##     selectionList        - the list of selected items to add to
        ##     worldSpaceSelectPts  -
        ##

        selected = False
        view = selectInfo.view()
        path = selectInfo.multiPath()
        singleSelection = selectInfo.singleSelection()

        ## Create a component that will store the selected vertices
        ##
        fnComponent = om.MFnSingleIndexedComponent()
        surfaceComponent = fnComponent.create( om.MFn.kMeshVertComponent )

        ## if the user did a single mouse click and we find > 1 selection
        ## we will use the alignmentMatrix to find out which is the closest
        ##
        alignmentMatrix = om.MMatrix()
        if singleSelection:
            alignmentMatrix = selectInfo.getAlignmentMatrix()

        singlePoint = om.MPoint()
        selectionPoint = om.MPoint()
        closestPointVertexIndex = -1
        previousZ = 0

        ## Get the geometry information
        ##
        meshNode = self.surfaceShape()
        geom = meshNode.meshGeom()

        ## Loop through all vertices of the mesh and
        ## see if they lie withing the selection area
        ##
        for currentPoint in geom.vertices:
            ## Sets OpenGL's render mode to select and stores
            ## selected items in a pick buffer
            ##
            view.beginSelect()

            glBegin( GL_POINTS )
            glVertex3f( currentPoint[0], currentPoint[1], currentPoint[2] )
            glEnd()

            if view.endSelect() > 0: ## Hit count > 0
                selected = True

                if singleSelection:
                    xformedPoint = currentPoint
                    xformedPoint.homogenize()
                    xformedPoint *= alignmentMatrix
                    z = xformedPoint.z
                    if closestPointVertexIndex < 0 or z > previousZ:
                        closestPointVertexIndex = vertexIndex
                        singlePoint = currentPoint
                        previousZ = z

                else:
                    ## multiple selection, store all elements
                    ##
                    fnComponent.addElement( vertexIndex )

        ## If single selection, insert the closest point into the array
        ##
        if selected and singleSelection:
            fnComponent.addElement(closestPointVertexIndex)

            ## need to get world space position for this vertex
            ##
            selectionPoint = singlePoint
            selectionPoint *= path.inclusiveMatrix()

        ## Add the selected component to the selection list
        ##
        if selected:
            selectionItem = om.MSelectionList()
            selectionItem.add( path, surfaceComponent )

            mask = om.MSelectionMask( om.MSelectionMask.kSelectComponentsMask )
            selectInfo.addSelection( selectionItem, selectionPoint, selectionList, worldSpaceSelectPts, mask, True )

        return selected

    def drawUVWireframe(self, geom, view, info):
        ##
        ## Description: 
        ##  Draws the UV layout in wireframe mode. 
        ## 

        view.beginGL()
        
        ## Draw the polygons
        ##
        vid = 0
        vid_start = vid
        for i in range(geom.faceCount):
            glBegin( GL_LINES )

            vid_start = vid 
            for v in range(geom.face_counts[i]-1):
                uvId1 = geom.uvcoords.uvId(vid)
                uvId2 = geom.uvcoords.uvId(vid+1)

                uv1 = geom.uvcoords.getUV(uvId1)
                uv2 = geom.uvcoords.getUV(uvId2)

                glVertex3f( uv1[0], uv1[1], 0.0 ) 
                glVertex3f( uv2[0], uv2[1], 0.0 ) 
                vid += 1
            
            uvId1 = geom.uvcoords.uvId(vid)
            uvId2 = geom.uvcoords.uvId(vid_start)

            uv1 = geom.uvcoords.getUV(uvId1)
            uv2 = geom.uvcoords.getUV(uvId2)

            glVertex3f( uv1[0], uv1[1], 0.0 ) 
            glVertex3f( uv2[0], uv2[1], 0.0 ) 
            vid += 1

            glEnd()
        
        view.endGL()

    def drawUVMapCoord(self, view, uvId, uv, drawNumbers):
        ##
        ## Description: 
        ##  Draw the specified uv value into the port view. If drawNumbers is True 
        ##  It will also draw the UV id for the the UV.  
        ##

        if drawNumbers:
            view.drawText( str(uvId), om.MPoint( uv[0], uv[1], 0 ), omui.M3dView.kCenter )

        glVertex3f( uv[0], uv[1], 0.0 )

    def drawUVMapCoordNum(self, geom, view, info, drawNumbers):
        ##
        ## Description: 
        ##  Draw the UV points for all uvs on this surface shape. 
        ##

        view.beginGL() 

        ptSize = glGetFloatv( GL_POINT_SIZE )
        glPointSize( 4.0 )

        for uvId in range(geom.uvcoords.uvcount()):
            uv = geom.uvcoords.getUV( uvId )
            self.drawUVMapCoord( view, uvId, uv, drawNumbers )

        glPointSize( ptSize )

        view.endGL() 
        
################################################################################
##
## apiMeshCreator
##
## A DG node that takes a maya mesh as input and outputs apiMeshData.
## If there is no input then the node creates a cube or sphere
## depending on what the shapeType attribute is set to.
##
################################################################################
class apiMeshCreator(om.MPxNode):
    id = om.MTypeId(0x8008A)

    ##########################################################
    ##
    ## Attributes
    ##
    ##########################################################
    size = None
    shapeType = None
    inputMesh = None
    outputSurface = None

    @staticmethod
    def creator():
        return apiMeshCreator()

    @staticmethod
    def initialize():
        typedAttr = om.MFnTypedAttribute()
        numericAttr = om.MFnNumericAttribute()
        enumAttr = om.MFnEnumAttribute()

        ## ----------------------- INPUTS -------------------------
        apiMeshCreator.size = numericAttr.create( "size", "sz", om.MFnNumericData.kDouble, 1 )
        numericAttr.array = False
        numericAttr.usesArrayDataBuilder = False
        numericAttr.hidden = False
        numericAttr.keyable = True
        om.MPxNode.addAttribute( apiMeshCreator.size )

        apiMeshCreator.shapeType = enumAttr.create( "shapeType", "st", 0 )
        enumAttr.addField( "cube", 0 )
        enumAttr.addField( "sphere", 1 )
        enumAttr.hidden = False
        enumAttr.keyable = True
        om.MPxNode.addAttribute( apiMeshCreator.shapeType )
        
        apiMeshCreator.inputMesh = typedAttr.create( "inputMesh", "im", om.MFnData.kMesh, om.MObject.kNullObj )
        typedAttr.hidden = True
        om.MPxNode.addAttribute( apiMeshCreator.inputMesh )

        ## ----------------------- OUTPUTS -------------------------
        apiMeshCreator.outputSurface = typedAttr.create( "outputSurface", "os", apiMeshData.id, om.MObject.kNullObj )
        typedAttr.writable = False
        om.MPxNode.addAttribute( apiMeshCreator.outputSurface )

        ## ---------- Specify what inputs affect the outputs ----------
        ##
        om.MPxNode.attributeAffects( apiMeshCreator.inputMesh, apiMeshCreator.outputSurface )
        om.MPxNode.attributeAffects( apiMeshCreator.size, apiMeshCreator.outputSurface )
        om.MPxNode.attributeAffects( apiMeshCreator.shapeType, apiMeshCreator.outputSurface )

    def __init__(self):
        om.MPxNode.__init__(self)

    ##########################################################
    ##
    ## Overrides
    ##
    ##########################################################

    def compute(self, plug, datablock):
        ##
        ## Description
        ##
        ##    When input attributes are dirty this method will be called to
        ##    recompute the output attributes.
        ##

        if plug == apiMeshCreator.outputSurface:
            ## Create some user defined geometry data and access the
            ## geometry so we can set it
            ##
            fnDataCreator = om.MFnPluginData()
            fnDataCreator.create( apiMeshData.id )

            newData = fnDataCreator.data()
            if not isinstance(newData, apiMeshData):
                raise RuntimeError("compute : invalid proxy cached apiMeshData object")

            geometry = newData.fGeometry

            ## If there is an input mesh then copy it's values
            ## and construct some apiMeshGeom for it.
            ##
            hasHistory = self.computeInputMesh( plug, datablock, geometry )
                                                
            ## There is no input mesh so check the shapeType attribute
            ## and create either a cube or a sphere.
            ##
            if not hasHistory:
                sizeHandle = datablock.inputValue( apiMeshCreator.size )
                shape_size = sizeHandle.asDouble()
                typeHandle = datablock.inputValue( apiMeshCreator.shapeType )
                shape_type = typeHandle.asShort()

                if shape_type == 0: ## build a cube
                    self.buildCube( shape_size, geometry )
                elif shape_type == 1: ## build a sphere
                    self.buildSphere( shape_size, 32, geometry )

            geometry.faceCount = len(geometry.face_counts)

            ## Assign the new data to the outputSurface handle
            ##
            outHandle = datablock.outputValue( apiMeshCreator.outputSurface )
            outHandle.setMPxData( newData )
            datablock.setClean( plug )

            # The plug was computed successfully
            return self

        # Let the Maya parent class compute the plug
        return None

    ##########################################################
    ##
    ## Helper methods
    ##
    ##########################################################

    def computeInputMesh(self, plug, datablock, geometry):
        ##
        ## Description
        ##
        ##     This function takes an input surface of type kMeshData and converts
        ##     the geometry into this nodes attributes.
        ##     Returns kFailure if nothing is connected.
        ##

        ## Get the input subdiv
        ##        
        inputData = datablock.inputValue( apiMeshCreator.inputMesh )
        surf = inputData.asMesh()

        ## Check if anything is connected
        ##
        thisObj = self.thisMObject()
        surfPlug = om.MPlug( thisObj, apiMeshCreator.inputMesh )
        if not surfPlug.isConnected:
            datablock.setClean( plug )
            return False

        ## Extract the mesh data
        ##
        surfFn = om.MFnMesh(surf)
        geometry.vertices = surfFn.getPoints(om.MSpace.kObject)

        ## Check to see if we have UVs to copy. 
        ##
        hasUVs = surfFn.numUVs() > 0
        uvs = surfFn.getUVs()
        geometry.uvcoords.ucoord = uvs[0]
        geometry.uvcoords.vcoord = uvs[1]

        for i in range(surfFn.numPolygons()):
            polyVerts = surfFn.getPolygonVertices(i)

            pvc = len(polyVerts)
            geometry.face_counts.append( pvc )

            for v in range(pvc):
                if hasUVs:
                    uvId = surfFn.getPolygonUVid(i, v)
                    geometry.uvcoords.faceVertexIndex.append( uvId )
                geometry.face_connects.append( polyVerts[v] )

        for n in range(len(geometry.vertices)):
            normal = surfFn.getVertexNormal(n)
            geometry.normals.append( normal )

        return True

    def buildCube(self, cube_size, geometry):
        ##
        ## Description
        ##
        ##    Constructs a cube
        ##

        geometry.vertices.clear()
        geometry.normals.clear()
        geometry.face_counts.clear()
        geometry.face_connects.clear()
        geometry.uvcoords.reset()

        geometry.vertices.append( om.MPoint( -cube_size, -cube_size, -cube_size ) )
        geometry.vertices.append( om.MPoint(  cube_size, -cube_size, -cube_size ) )
        geometry.vertices.append( om.MPoint(  cube_size, -cube_size, cube_size ) )
        geometry.vertices.append( om.MPoint( -cube_size, -cube_size, cube_size ) )
        geometry.vertices.append( om.MPoint( -cube_size, cube_size, -cube_size ) )
        geometry.vertices.append( om.MPoint( -cube_size, cube_size, cube_size ) )
        geometry.vertices.append( om.MPoint(  cube_size, cube_size, cube_size ) )
        geometry.vertices.append( om.MPoint(  cube_size, cube_size, -cube_size ) )

        normal_value = 0.5775
        geometry.normals.append( om.MVector( -normal_value, -normal_value, -normal_value ) )
        geometry.normals.append( om.MVector(  normal_value, -normal_value, -normal_value ) )
        geometry.normals.append( om.MVector(  normal_value, -normal_value, normal_value ) )
        geometry.normals.append( om.MVector( -normal_value, -normal_value, normal_value ) )
        geometry.normals.append( om.MVector( -normal_value, normal_value, -normal_value ) )
        geometry.normals.append( om.MVector( -normal_value, normal_value, normal_value ) )
        geometry.normals.append( om.MVector(  normal_value, normal_value, normal_value ) )
        geometry.normals.append( om.MVector(  normal_value, normal_value, -normal_value ) )

        ## Define the UVs for the cube. 
        ##
        uv_count = 14
        uv_pts = [  [ 0.375, 0.0  ],
                    [ 0.625, 0.0  ],
                    [ 0.625, 0.25 ],
                    [ 0.375, 0.25 ],
                    [ 0.625, 0.5  ],
                    [ 0.375, 0.5  ],
                    [ 0.625, 0.75 ],
                    [ 0.375, 0.75 ],
                    [ 0.625, 1.0  ],
                    [ 0.375, 1.0  ],
                    [ 0.875, 0.0  ],
                    [ 0.875, 0.25 ],
                    [ 0.125, 0.0  ],
                    [ 0.125, 0.25 ] ]
        
        ## UV Face Vertex Id. 
        ##
        num_face_connects = 24
        uv_fvid = [ 0, 1, 2, 3, 
                    3, 2, 4, 5, 
                    5, 4, 6, 7, 
                    7, 6, 8, 9, 
                    1, 10, 11, 2, 
                    12, 0, 3, 13 ]

        for i in range(uv_count):
            geometry.uvcoords.append_uv( uv_pts[i][0], uv_pts[i][1] )
        
        for i in range(num_face_connects):
            geometry.uvcoords.faceVertexIndex.append( uv_fvid[i] ) 

        ## Set up an array containing the number of vertices
        ## for each of the 6 cube faces (4 verticies per face)
        ##
        num_faces = 6
        face_counts = [ 4, 4, 4, 4, 4, 4 ]

        for i in range(num_faces):
            geometry.face_counts.append( face_counts[i] )

        ## Set up and array to assign vertices from vertices to each face 
        ##
        face_connects =   [ 0, 1, 2, 3,
                            4, 5, 6, 7,
                            3, 2, 6, 5,
                            0, 3, 5, 4,
                            0, 4, 7, 1,
                            1, 7, 6, 2 ]

        for i in range(num_face_connects):
            geometry.face_connects.append( face_connects[i] )

    def buildSphere(self, radius, divisions, geometry):
        ##
        ## Description
        ##
        ##    Create circles of vertices starting with 
        ##    the top pole ending with the botton pole
        ##

        geometry.vertices.clear()
        geometry.normals.clear()
        geometry.face_counts.clear()
        geometry.face_connects.clear()
        geometry.uvcoords.reset()

        u = -math.pi / 2.
        v = -math.pi
        u_delta = math.pi / divisions
        v_delta = 2 * math.pi / divisions

        topPole = om.MPoint( 0.0, radius, 0.0 )
        botPole = om.MPoint( 0.0, -radius, 0.0 )

        ## Build the vertex and normal table
        ##
        geometry.vertices.append( botPole )
        geometry.normals.append( botPole - om.MPoint.kOrigin )

        for i in range(divisions-1):
            u += u_delta
            v = -math.pi

            for j in range(divisions):
                x = radius * math.cos(u) * math.cos(v)
                y = radius * math.sin(u)
                z = radius * math.cos(u) * math.sin(v)

                pnt = om.MPoint( x, y, z )
                geometry.vertices.append( pnt )
                geometry.normals.append( pnt - om.MPoint.kOrigin )
                v += v_delta

        geometry.vertices.append( topPole )
        geometry.normals.append( topPole - om.MPoint.kOrigin )

        ## Create the connectivity lists
        ##
        vid = 1
        numV = 0
        for i in range(divisions):
            for j in range(divisions):
                if i == 0:
                    geometry.face_counts.append( 3 )

                    geometry.face_connects.append( 0 )
                    geometry.face_connects.append( j + vid )
                    if j == divisions-1:
                        geometry.face_connects.append( vid )
                    else:
                        geometry.face_connects.append( j + vid + 1 )

                elif i == divisions-1:
                    geometry.face_counts.append( 3 )

                    geometry.face_connects.append( j + vid + 1 - divisions )
                    geometry.face_connects.append( vid + 1 )
                    if j == divisions-1:
                        geometry.face_connects.append( vid + 1 - divisions )
                    else:
                        geometry.face_connects.append( j + vid + 2 - divisions )

                else:
                    geometry.face_counts.append( 4 )

                    geometry.face_connects.append( j + vid + 1 - divisions )
                    geometry.face_connects.append( j + vid + 1 )
                    if j == divisions-1:
                        geometry.face_connects.append( vid + 1 )
                        geometry.face_connects.append( vid + 1 - divisions )
                    else:
                        geometry.face_connects.append( j + vid + 2 )
                        geometry.face_connects.append( j + vid + 2 - divisions )

                numV += 1

            vid = numV

## Helper class for link lost callback
class ShadedItemUserData(om.MUserData):
    def __init__(self, override):
        om.MUserData.__init__(self, legacy=False)
        self.fOverride = override

## Custom user data class to attach to face selection render item
## to help with viewport 2.0 selection
class apiMeshHWSelectionUserData(om.MUserData):
    def __init__(self):
        om.MUserData.__init__(self, legacy=False)   ## let Maya clean up
        self.fMeshGeom = None
        self.fInstanceIndex = 0
        self.fFaceViewSelectedStates = None

        
sViewSelectedInstanceMark = -1      
sViewSelectedFaceSelectionNames = set()
        
# Gather the view-selected face indices of each instance. Use -1 to mark a  
# view-selected instance (but not any of its faces) for easier processing
# later in shouldDrawInstance().
def gatherViewSelectedFaceInfo(frameContext, instances, meshGeom):
    viewSelectedFaceInfo = collections.defaultdict(list)
    
    if (not meshGeom or meshGeom.faceCount <= 0):
        return False, viewSelectedFaceInfo

    renderingDestinationResult = frameContext.renderingDestination()
    
    if (renderingDestinationResult[0] != omr.MFrameContext.k3dViewport):
        return False, viewSelectedFaceInfo

    view = omui.M3dView.getM3dViewFromModelPanel(renderingDestinationResult[1])

    if(not view or not view.viewIsFiltered()):
        return False, viewSelectedFaceInfo
    
        
    viewSelectedList = view.filteredObjectList()
    if(viewSelectedList):
        
        for instIdx in range(len(instances)):
            intersectionList = om.MSelectionList()
            
            intersectionList.add(instances[instIdx])
            intersectionList.intersect(viewSelectedList, True)
            
            selectionIt = om.MItSelectionList(intersectionList)
            while not selectionIt.isDone():
                comp = selectionIt.getComponent()[1]
                
                if(comp.isNull()):
                    viewSelectedFaceInfo[instIdx].append(sViewSelectedInstanceMark)
                    
                else:
                    fnComp = om.MFnSingleIndexedComponent(comp)     
                    
                    if (fnComp.componentType == om.MFn.kMeshPolygonComponent):
                        faceIds = fnComp.getElements()
                        
                        for i in range(len(faceIds)):
                            faceId = faceIds[i]
                            if (faceId >= 0 and faceId < meshGeom.faceCount):
                                viewSelectedFaceInfo[instIdx].append(faceId)
                
                next(selectionIt)
                
    return True, viewSelectedFaceInfo

# If an instance has only -1 stored in its ViewSelectedFaceInfo map, it is
# view-selected but none of its faces is, so the instance should be drawn.
def shouldDrawInstance(viewSelectedFaceInfo, instIdx):
    found = False
    
    if instIdx in viewSelectedFaceInfo:
        faceIds = viewSelectedFaceInfo[instIdx]
        
        for id in faceIds:
            if id != sViewSelectedInstanceMark:
                return False
            found = True
    
    return found
    
################################################################################
##
## apiMeshSubSceneOverride
##
## Handles vertex data preparation for drawing the user defined shape in
## Viewport 2.0.
##
################################################################################
## Custom component converter to select components
## Attached to the vertex, edge and face selection render items
## respectively apiMeshSubSceneOverride.sVertexSelectionName, apiMeshSubSceneOverride.sEdgeSelectionName
## and apiMeshSubSceneOverride.sFaceSelectionName
class simpleComponentConverterSubsceneOverride(omr.MPxComponentConverter):
    def __init__(self, componentType, selectionType):
        omr.MPxComponentConverter.__init__(self)

        self.fComponentType = componentType
        self.fSelectionType = selectionType

        self.fComponent = om.MFnSingleIndexedComponent()
        self.fComponentObject = om.MObject.kNullObj
        self.fLookupTable = []

    def initialize(self, renderItem):
        ## Create the component selection object
        self.fComponentObject = self.fComponent.create( self.fComponentType )

        ## For face selection, 
        ## create a lookup table to match triangle intersection with face id :
        ## One face may contains more than one triangle
        if self.fComponentType == om.MFn.kMeshPolygonComponent:
            selectionData = renderItem.getCustomData()
            if isinstance(selectionData, apiMeshHWSelectionUserData):
                meshGeom = selectionData.fMeshGeom
                faceStates = selectionData.fFaceViewSelectedStates

                ## Allocate faces lookup table
                numTriangles = 0
                for i in range(meshGeom.faceCount):
                    numVerts = meshGeom.face_counts[i]
                    if numVerts > 2:
                        if(not faceStates or faceStates[i]):
                            numTriangles += numVerts - 2
                
                self.fLookupTable = [0]*numTriangles

                ## Fill faces lookup table
                triId = 0
                for faceId in range(meshGeom.faceCount):
                    ## ignore degenerate faces
                    numVerts = meshGeom.face_counts[faceId]
                    if numVerts > 2:
                        if(not faceStates or faceStates[faceId]):
                            for v in range(1, numVerts-1):
                                self.fLookupTable[triId] = faceId
                                triId += 1

    def addIntersection(self, intersection):
        ## Convert the intersection index, which represent the primitive position in the
        ## index buffer, to the correct component id

        ## For vertex and edge: the primitive index value is the same as the component id
        ## For face: get the face id that matches the triangle index from the lookup table

        if self.fComponentType == om.MFn.kMeshEdgeComponent:
            # Only accept edge selection intersection on draw instance #2 -- scaled by 2
            # and instance #-1 (when useDrawInstancingOnEdgeSelectionItem is False)
            if intersection.instanceID == 1 or intersection.instanceID == 3:
                return

        idx = intersection.index

        if self.fComponentType == om.MFn.kMeshPolygonComponent:
            if idx >= 0 and idx < len(self.fLookupTable):
                idx = self.fLookupTable[idx]

        self.fComponent.addElement(idx)

    def component(self):
        ## Return the component object that contains the ids of the selected components
        return self.fComponentObject

    def selectionMask(self):
        ## This converter is only valid for specified selection type
        return self.fSelectionType

    ## creator function to instanciate a component converter for vertex selection
    @staticmethod
    def creatorVertexSelection():
        mask = om.MSelectionMask(om.MSelectionMask.kSelectMeshVerts)
        mask.addMask(om.MSelectionMask.kSelectPointsForGravity)
        return simpleComponentConverterSubsceneOverride(om.MFn.kMeshVertComponent, mask)

    ## creator function to instanciate a component converter for edge selection
    @staticmethod
    def creatorEdgeSelection():
        return simpleComponentConverterSubsceneOverride(om.MFn.kMeshEdgeComponent, om.MSelectionMask.kSelectMeshEdges)

    ## creator function to instanciate a component converter for face selection
    @staticmethod
    def creatorFaceSelection():
        return simpleComponentConverterSubsceneOverride(om.MFn.kMeshPolygonComponent, om.MSelectionMask.kSelectMeshFaces)

class apiMeshSubSceneOverride(omr.MPxSubSceneOverride):
    sWireName        = "apiMeshWire_subscene_py"
    sSelectName      = "apiMeshSelection_subscene_py"
    sBoxName         = "apiMeshBox_subscene_py"
    sSelectedBoxName = "apiMeshBoxSelection_subscene_py"
    sShadedName      = "apiMeshShaded_subscene_py"
    sTexturedName    = "apiMeshTextured_subscene_py"

    sVertexSelectionName = "apiMeshVertexSelection_subscene_py"
    sEdgeSelectionName   = "apiMeshEdgeSelection_subscene_py"
    sFaceSelectionName   = "apiMeshFaceSelection_subscene_py"

    sActiveVertexName = "apiMeshActiveVertex_subscene_py"
    sActiveEdgeName   = "apiMeshActiveEdge_subscene_py"
    sActiveFaceName   = "apiMeshActiveFace_subscene_py"
    
    sNameSeparator    = "_"
    
    class InstanceInfo(object):
        def __init__(self, transform, isSelected):
            self.fTransform = transform
            self.fIsSelected = isSelected

    @staticmethod
    def creator(obj):
        return apiMeshSubSceneOverride(obj)

    @staticmethod
    def shadedItemLinkLost(userData):
        if not userData is None and not userData.fOverride is None:
            if not userData.fOverride.fMesh is None:
                userData.fOverride.fMesh.setMaterialDirty(True)
            userData.fOverride = None
        userData = None

    def __init__(self, obj):
        omr.MPxSubSceneOverride.__init__(self, obj)
        
        node = om.MFnDependencyNode(obj)
        self.fMesh = node.userNode()
        self.fObject = om.MObject(obj)
        self.fWireShader = None
        self.fThickWireShader = None
        self.fSelectShader = None
        self.fThickSelectShader = None
        self.fShadedShader = None
        self.fVertexComponentShader = None
        self.fEdgeComponentShader = None
        self.fFaceComponentShader = None
        self.fPositionBuffer = None
        self.fNormalBuffer = None
        self.fBoxPositionBuffer = None
        self.fWireIndexBuffer = None
        self.fBoxIndexBuffer = None
        self.fShadedIndexBuffer = None
        self.fActiveVerticesIndexBuffer = None
        self.fActiveEdgesIndexBuffer = None
        self.fActiveFacesIndexBuffer = None
        self.fThickLineWidth = -1.0
        self.fQueuedLineWidth = -1.0
        self.fNumInstances = 0
        self.fIsInstanceMode = False
        self.fQueueUpdate = False
        self.fUseQueuedLineUpdate = False ## Set to True to run sample line width update code

        self.fInstanceInfoCache = collections.defaultdict(set)

        self.fActiveVerticesSet = set()
        self.fActiveEdgesSet = set()
        self.fActiveFacesSet = set()
        
        self.fViewSelectedFaceInfoCache = collections.defaultdict(list)
        self.fLinkLostCallbackData      = []

    def __del__(self):
        self.fMesh = None

        shaderMgr = omr.MRenderer.getShaderManager()
        if shaderMgr:
            if self.fWireShader:
                shaderMgr.releaseShader(self.fWireShader)
                self.fWireShader = None

            if self.fThickWireShader:
                shaderMgr.releaseShader(self.fThickWireShader)
                self.fThickWireShader = None

            if self.fSelectShader:
                shaderMgr.releaseShader(self.fSelectShader)
                self.fSelectShader = None

            if self.fThickSelectShader:
                shaderMgr.releaseShader(self.fThickSelectShader)
                self.fThickSelectShader = None

            if self.fShadedShader:
                shaderMgr.releaseShader(self.fShadedShader)
                self.fShadedShader = None

            if self.fVertexComponentShader:
                shaderMgr.releaseShader(self.fVertexComponentShader)
                self.fVertexComponentShader = None

            if self.fEdgeComponentShader:
                shaderMgr.releaseShader(self.fEdgeComponentShader)
                self.fEdgeComponentShader = None

            if self.fFaceComponentShader:
                shaderMgr.releaseShader(self.fFaceComponentShader)
                self.fFaceComponentShader = None

        self.clearBuffers()

    def supportedDrawAPIs(self):
        ## this plugin supports both GL and DX
        return omr.MRenderer.kOpenGL | omr.MRenderer.kDirectX11 | omr.MRenderer.kOpenGLCoreProfile

    def requiresUpdate(self, container, frameContext):
        # Nothing in the container, definitely need to update
        if len(container) == 0:
            return True

        # Update always. This could be optimized to only update when the
        # actual shape node detects a change.
        return True

    def update(self, container, frameContext):
        # Update render items based on current set of instances
        self.manageRenderItems(container, frameContext, self.fMesh.shapeDirty() or len(container) == 0)

        # Always reset shape dirty flag
        self.fMesh.resetShapeDirty()

    def furtherUpdateRequired(self, frameContext):
        if self.fUseQueuedLineUpdate:
            if not frameContext.inUserInteraction() and not frameContext.userChangingViewContext():
                return self.fQueueUpdate

        return False

    def manageRenderItems(self, container, frameContext, updateGeometry):
        ## Preamble
        if not self.fMesh or self.fObject.isNull():
            return

        shaderMgr = omr.MRenderer.getShaderManager()
        if not shaderMgr:
            return

        node = om.MFnDagNode(self.fObject)
        instances = node.getAllPaths()
        if len(instances) == 0:
            return

        ## Constants
        sRed     = [1.0, 0.0, 0.0, 1.0]
        sGreen   = [0.0, 1.0, 0.0, 1.0]
        sWhite   = [1.0, 1.0, 1.0, 1.0]

        ## Set up shared shaders if needed
        if not self.fWireShader:
            self.fWireShader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader)
            self.fWireShader.setParameter("solidColor", sRed)

        if not self.fThickWireShader:
            self.fThickWireShader = shaderMgr.getStockShader(omr.MShaderManager.k3dThickLineShader)
            self.fThickWireShader.setParameter("solidColor", sRed)

        if not self.fSelectShader:
            self.fSelectShader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader)
            self.fSelectShader.setParameter("solidColor", sGreen)

        if not self.fThickSelectShader:
            self.fThickSelectShader = shaderMgr.getStockShader(omr.MShaderManager.k3dThickLineShader)
            self.fThickSelectShader.setParameter("solidColor", sGreen)

        if not self.fVertexComponentShader:
            self.fVertexComponentShader = shaderMgr.getStockShader(omr.MShaderManager.k3dFatPointShader)
            self.fVertexComponentShader.setParameter("solidColor", sWhite)
            self.fVertexComponentShader.setParameter("pointSize", [5.0, 5.0])

        if not self.fEdgeComponentShader:
            self.fEdgeComponentShader = shaderMgr.getStockShader(omr.MShaderManager.k3dThickLineShader)
            self.fEdgeComponentShader.setParameter("solidColor", sWhite)
            self.fEdgeComponentShader.setParameter("lineWidth", [2.0, 2.0])

        if not self.fFaceComponentShader:
            self.fFaceComponentShader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader)
            self.fFaceComponentShader.setParameter("solidColor", sWhite)

        if not self.fShadedShader:
            self.fShadedShader = shaderMgr.getStockShader(omr.MShaderManager.k3dBlinnShader)

        ## Set up shared geometry if necessary
        if updateGeometry:
            self.rebuildGeometryBuffers()

        if not all((self.fPositionBuffer, self.fNormalBuffer, self.fBoxPositionBuffer, self.fWireIndexBuffer, self.fBoxIndexBuffer, self.fShadedIndexBuffer)):
            return
        
        isActiveViewFiltered, viewSelectedFaceInfo = gatherViewSelectedFaceInfo(frameContext, instances, self.fMesh.meshGeom()) 
        
        selectedList = om.MGlobal.getActiveSelectionList()

        anyMatrixChanged = False
        itemsChanged = False
        instanceArrayLength = len(instances)
        numInstanceSelected = 0
        numInstanceUnselected = 0
        numInstances = 0

        instanceMatrixArray = om.MMatrixArray(instanceArrayLength)
        selectedInstanceMatrixArray = om.MMatrixArray(instanceArrayLength)
        unselectedInstanceMatrixArray = om.MMatrixArray(instanceArrayLength)

        for instIdx in range(instanceArrayLength):
            ## If expecting large numbers of instances, then walking through the whole
            ## list of instances every time to look for changes is not efficient
            ## enough.  Watching for change events and changing only the required
            ## instances should be done instead.  This method of checking for selection
            ## status is also not fast.
            instance = instances[instIdx]
            instanceNum = instance.instanceNumber()

            if (instance.isValid and instance.isVisible and (not isActiveViewFiltered or shouldDrawInstance(viewSelectedFaceInfo, instIdx))):
                instanceInfo = apiMeshSubSceneOverride.InstanceInfo(instance.inclusiveMatrix(), useSelectHighlight(selectedList, instance))

                if( instanceNum not in self.fInstanceInfoCache or 
                    self.fInstanceInfoCache[instanceNum].fIsSelected != instanceInfo.fIsSelected or 
                    not self.fInstanceInfoCache[instanceNum].fTransform.isEquivalent(instanceInfo.fTransform)):
                    
                    self.fInstanceInfoCache[instanceNum] = instanceInfo
                    anyMatrixChanged = True
                
                instanceMatrixArray[numInstances] = instanceInfo.fTransform
                numInstances += 1
                
                if instanceInfo.fIsSelected:
                    selectedInstanceMatrixArray[numInstanceSelected] = instanceInfo.fTransform
                    numInstanceSelected += 1
                else:
                    unselectedInstanceMatrixArray[numInstanceUnselected] = instanceInfo.fTransform
                    numInstanceUnselected += 1
            else:
                if (instanceNum in self.fInstanceInfoCache):
                    
                    del self.fInstanceInfoCache[instanceNum]
                    
                    anyMatrixChanged = True

        instanceMatrixArray.setLength(numInstances)  ## collapse to correct length
        selectedInstanceMatrixArray.setLength(numInstanceSelected)
        unselectedInstanceMatrixArray.setLength(numInstanceUnselected)
        if self.fNumInstances != numInstances:
            anyMatrixChanged = True
            self.fNumInstances = numInstances

        anyInstanceSelected = numInstanceSelected > 0
        anyInstanceUnselected = numInstanceUnselected > 0

        activeVerticesSet = set()
        activeEdgesSet = set()
        activeFacesSet = set()

        meshGeom = self.fMesh.meshGeom()
        if meshGeom and self.fMesh.hasActiveComponents():
            activeComponents = self.fMesh.activeComponents()
            if len(activeComponents) > 0:
                fnComponent = om.MFnSingleIndexedComponent( activeComponents[0] )
                if fnComponent.elementCount > 0:
                    activeIds = fnComponent.getElements()

                    if fnComponent.componentType == om.MFn.kMeshVertComponent:
                        activeVerticesSet = set(activeIds)

                    elif fnComponent.componentType == om.MFn.kMeshEdgeComponent:
                        activeEdgesSet = set(activeIds)

                    elif fnComponent.componentType == om.MFn.kMeshPolygonComponent:
                        activeFacesSet = set(activeIds)

        ## Update index buffer of active items if necessary
        updateActiveItems = updateGeometry or self.fActiveVerticesSet != activeVerticesSet or self.fActiveEdgesSet != activeEdgesSet or self.fActiveFacesSet != activeFacesSet
        self.fActiveVerticesSet = activeVerticesSet
        self.fActiveEdgesSet = activeEdgesSet
        self.fActiveFacesSet = activeFacesSet

        if updateActiveItems:
            self.rebuildActiveComponentIndexBuffers()

        anyVertexSelected = bool(self.fActiveVerticesSet)
        anyEdgeSelected = bool(self.fActiveEdgesSet)
        anyFaceSelected = bool(self.fActiveFacesSet)

        if (anyVertexSelected and not self.fActiveVerticesIndexBuffer) or (anyEdgeSelected and not self.fActiveEdgesIndexBuffer) or (anyFaceSelected and not self.fActiveFacesIndexBuffer):
            return

        ## Add render items if necessary.  Remove any pre-existing render items
        ## that are no longer needed.
        wireItem = container.find(self.sWireName)
        if not wireItem and anyInstanceUnselected:
            wireItem = omr.MRenderItem.create( self.sWireName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            wireItem.setDrawMode(omr.MGeometry.kWireframe)
            wireItem.setDepthPriority(omr.MRenderItem.sActiveWireDepthPriority)
            wireItem.setShader(self.fWireShader)
            container.add(wireItem)
            itemsChanged = True

        elif wireItem and not anyInstanceUnselected:
            container.remove(self.sWireName)
            wireItem = None
            itemsChanged = True

        selectItem = container.find(self.sSelectName)
        if not selectItem and anyInstanceSelected:
            selectItem = omr.MRenderItem.create( self.sSelectName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            selectItem.setDrawMode(omr.MGeometry.kWireframe | omr.MGeometry.kShaded | omr.MGeometry.kTextured)
            selectItem.setDepthPriority(omr.MRenderItem.sActiveWireDepthPriority)
            selectItem.setShader(self.fSelectShader)
            container.add(selectItem)
            itemsChanged = True

        elif selectItem and not anyInstanceSelected:
            container.remove(self.sSelectName)
            selectItem = None
            itemsChanged = True

        boxItem = container.find(self.sBoxName)
        if not boxItem and anyInstanceUnselected:
            boxItem = omr.MRenderItem.create( self.sBoxName, omr.MRenderItem.NonMaterialSceneItem, omr.MGeometry.kLines)
            boxItem.setDrawMode(omr.MGeometry.kBoundingBox)
            boxItem.setShader(self.fWireShader)
            container.add(boxItem)
            itemsChanged = True

        elif boxItem and not anyInstanceUnselected:
            container.remove(self.sBoxName)
            boxItem = None
            itemsChanged = True

        selectedBoxItem = container.find(self.sSelectedBoxName)
        if not selectedBoxItem and anyInstanceSelected:
            selectedBoxItem = omr.MRenderItem.create( self.sSelectedBoxName, omr.MRenderItem.NonMaterialSceneItem, omr.MGeometry.kLines)
            selectedBoxItem.setDrawMode(omr.MGeometry.kBoundingBox)
            selectedBoxItem.setShader(self.fSelectShader)
            container.add(selectedBoxItem)
            itemsChanged = True

        elif selectedBoxItem and not anyInstanceSelected:
            container.remove(self.sSelectedBoxName)
            selectedBoxItem = None
            itemsChanged = True

        shadedItem = container.find(self.sShadedName)
        if not shadedItem:
            ## We always want a shaded item
            shadedItem = omr.MRenderItem.create( self.sShadedName, omr.MRenderItem.MaterialSceneItem, omr.MGeometry.kTriangles)
            shadedItem.setDrawMode(omr.MGeometry.kShaded)
            shadedItem.setExcludedFromPostEffects(False)
            shadedItem.setCastsShadows(True)
            shadedItem.setReceivesShadows(True)
            container.add(shadedItem)
            itemsChanged = True

        texturedItem = container.find(self.sTexturedName)
        if not texturedItem:
            ## We always want a textured item
            texturedItem = omr.MRenderItem.create( self.sTexturedName, omr.MRenderItem.MaterialSceneItem, omr.MGeometry.kTriangles)
            texturedItem.setDrawMode(omr.MGeometry.kTextured)
            texturedItem.setExcludedFromPostEffects(False)
            texturedItem.setCastsShadows(True)
            texturedItem.setReceivesShadows(True)
            container.add(texturedItem)
            itemsChanged = True

        ## Grab shading node from first component of first instance of the
        ## object and use it to get an MShaderInstance. This could be expanded
        ## to support full instancing and components if necessary.
        try:
            shader = None
        
            connectedPlugs = om.MPlugArray()
            (sets, comps) = node.getConnectedSetsAndMembers(0, True)
            for obj in sets:
                dn = om.MFnDependencyNode(obj)
                shaderPlug = dn.findPlug("surfaceShader", True)
                connectedPlugs = shaderPlug.connectedTo(True, False)
                if len(connectedPlugs) > 0:
                    shader = connectedPlugs[0].node()
                    if(shader):
                        break
            
            ## Check the dirty flag and make necessary update for shader assignment.
            updateMaterial =  self.fMesh.materialDirty()
            self.fMesh.setMaterialDirty(False)
            
            ## Update shader for shaded item
            if updateMaterial or not shadedItem.isShaderFromNode():
                if not shader or \
                    not shadedItem.setShaderFromNode(shader, 
                                                    instances[0], 
                                                    apiMeshSubSceneOverride.shadedItemLinkLost, 
                                                    ShadedItemUserData(self), 
                                                    True):
                    shadedItem.setShader(self.fShadedShader)

            ## Update shader for textured item
            if updateMaterial or not texturedItem.isShaderFromNode():
                if not shader or \
                    not texturedItem.setShaderFromNode(shader,
                                                    instances[0],
                                                    apiMeshSubSceneOverride.shadedItemLinkLost,
                                                    ShadedItemUserData(self),
                                                    False):
                    texturedItem.setShader(self.fShadedShader)
        except:
            print("Unexpected error:", sys.exc_info()[0])
            pass

        # render item for vertex selection
        vertexSelectionItem = container.find(self.sVertexSelectionName)
        if not vertexSelectionItem:
            vertexSelectionItem = omr.MRenderItem.create( self.sVertexSelectionName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            # use for selection only : not visible in viewport
            vertexSelectionItem.setDrawMode(omr.MGeometry.kSelectionOnly)
            # set the selection mask to kSelectMeshVerts : we want the render item to be used for Vertex Components selection
            mask = om.MSelectionMask(om.MSelectionMask.kSelectMeshVerts)
            mask.addMask(om.MSelectionMask.kSelectPointsForGravity)
            vertexSelectionItem.setSelectionMask( mask )
            # set selection priority : on top
            vertexSelectionItem.setDepthPriority(omr.MRenderItem.sSelectionDepthPriority)
            vertexSelectionItem.setShader(self.fVertexComponentShader)
            container.add(vertexSelectionItem)
            itemsChanged = True

        # change this value to enable item instancing : same item will be rendered multiple times
        # the edge selection item will be visible in the viewport and rendered 3 times (with different scaling)
        # only the second instance (scale 1.5) will be selectable (see simpleComponentConverterSubsceneOverride)
        useDrawInstancingOnEdgeSelectionItem = False

        # render item for edge selection
        edgeSelectionItem = container.find(self.sEdgeSelectionName)
        if not edgeSelectionItem:
            # use for selection only : not visible in viewport
            drawMode = omr.MGeometry.kSelectionOnly
            depthPriority = omr.MRenderItem.sSelectionDepthPriority
            if useDrawInstancingOnEdgeSelectionItem:
                # display in viewport and in selection
                drawMode = omr.MGeometry.kAll
                # reduce priority so we can see the active item
                depthPriority = omr.MRenderItem.sActiveWireDepthPriority-1

            edgeSelectionItem = omr.MRenderItem.create( self.sEdgeSelectionName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            edgeSelectionItem.setDrawMode(drawMode)
            # set selection priority : on top
            edgeSelectionItem.setDepthPriority(depthPriority)
            # set the selection mask to kSelectMeshEdges : we want the render item to be used for Edge Components selection
            edgeSelectionItem.setSelectionMask( om.MSelectionMask.kSelectMeshEdges )
            edgeSelectionItem.setShader(self.fWireShader)
            container.add(edgeSelectionItem)
            itemsChanged = True

        # render item for face selection - not visible in viewport
        faceSelectionItem = container.find(self.sFaceSelectionName)
        if not faceSelectionItem:
            faceSelectionItem = omr.MRenderItem.create( self.sFaceSelectionName, omr.MRenderItem.DecorationItem, omr.MGeometry.kTriangles)
            # use for selection only : not visible in viewport
            faceSelectionItem.setDrawMode(omr.MGeometry.kSelectionOnly)
            # set the selection mask to kSelectMeshFaces : we want the render item to be used for Face Components selection
            faceSelectionItem.setSelectionMask( om.MSelectionMask.kSelectMeshFaces )
            # set selection priority : on top
            faceSelectionItem.setDepthPriority(omr.MRenderItem.sSelectionDepthPriority)
            faceSelectionItem.setShader(self.fFaceComponentShader)
            container.add(faceSelectionItem)
            itemsChanged = True

        ## create and add a custom data to help the face component converter
        if updateGeometry:
            mySelectionData = apiMeshHWSelectionUserData()
            mySelectionData.fMeshGeom = self.fMesh.meshGeom()
            faceSelectionItem.setCustomData(mySelectionData)

        # render item to display active (selected) vertices
        activeVertexItem = container.find(self.sActiveVertexName)
        if not activeVertexItem and anyVertexSelected:
            activeVertexItem = omr.MRenderItem.create( self.sActiveVertexName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            activeVertexItem.setDrawMode(omr.MGeometry.kAll)
            activeVertexItem.setDepthPriority(omr.MRenderItem.sActivePointDepthPriority)
            activeVertexItem.setShader(self.fVertexComponentShader)
            container.add(activeVertexItem)
            itemsChanged = True

        elif activeVertexItem and not anyVertexSelected:
            container.remove(self.sActiveVertexName)
            activeVertexItem = None
            itemsChanged = True

        # render item to display active (selected) edges
        activeEdgeItem = container.find(self.sActiveEdgeName)
        if not activeEdgeItem and anyEdgeSelected:
            activeEdgeItem = omr.MRenderItem.create( self.sActiveEdgeName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            activeEdgeItem.setDrawMode(omr.MGeometry.kAll)
            activeEdgeItem.setDepthPriority(omr.MRenderItem.sActiveLineDepthPriority)
            activeEdgeItem.setShader(self.fEdgeComponentShader)
            container.add(activeEdgeItem)
            itemsChanged = True

        elif activeEdgeItem and not anyEdgeSelected:
            container.remove(self.sActiveEdgeName)
            activeEdgeItem = None
            itemsChanged = True

        # render item to display active (selected) faces
        activeFaceItem = container.find(self.sActiveFaceName)
        if not activeFaceItem and anyFaceSelected:
            activeFaceItem = omr.MRenderItem.create( self.sActiveFaceName, omr.MRenderItem.DecorationItem, omr.MGeometry.kTriangles)
            activeFaceItem.setDrawMode(omr.MGeometry.kAll)
            activeFaceItem.setDepthPriority(omr.MRenderItem.sActiveLineDepthPriority)
            activeFaceItem.setShader(self.fFaceComponentShader)
            container.add(activeFaceItem)
            itemsChanged = True

        elif activeFaceItem and not anyFaceSelected:
            container.remove(self.sActiveFaceName)
            activeFaceItem = None
            itemsChanged = True

        ## update the line width on the shader for our wire items if it changed
        lineWidth = frameContext.getGlobalLineWidth()
        userWidthChange = not floatApproxEqual(lineWidth, self.fThickLineWidth)

        doUpdate = False
        targetRefinedLineWidth = 50.0
        if userWidthChange:
            self.fThickLineWidth = lineWidth
            doUpdate = True

            ## First user change will trigger an update requirement
            if self.fUseQueuedLineUpdate:
                self.fQueuedLineWidth = lineWidth
                if self.fQueuedLineWidth < targetRefinedLineWidth:
                    self.fQueueUpdate = True

        else:
            ## Increment by 1 until we reach the target width.
            ## If we haven't reached it yet then queue another update
            ## so we can increment and retest against the target width.
            if self.fUseQueuedLineUpdate and self.fQueueUpdate:
                if self.fQueuedLineWidth < targetRefinedLineWidth:
                    lineWidth = self.fQueuedLineWidth
                    self.fQueuedLineWidth += 1
                    self.fQueueUpdate = True
                    doUpdate = True

                else:
                    ## Reached target. Stop asking for more refinement
                    self.fQueueUpdate = False
        
        if doUpdate:
            if not floatApproxEqual(lineWidth, 1.0):
                ## Only set the shader if the line width changes (or the first time)
                lineWidthArray = [ lineWidth, lineWidth ]
                self.fThickWireShader.setParameter("lineWidth", lineWidthArray)
                self.fThickSelectShader.setParameter("lineWidth", lineWidthArray)
                if wireItem:
                    wireItem.setShader(self.fThickWireShader)
                if selectItem:
                    selectItem.setShader(self.fThickSelectShader)

            else:
                if wireItem:
                    wireItem.setShader(self.fWireShader)
                if selectItem:
                    selectItem.setShader(self.fSelectShader)

        ## Update geometry if required
        if itemsChanged or updateGeometry:
            bounds = self.fMesh.boundingBox()

            wireBuffers = omr.MVertexBufferArray()
            wireBuffers.append(self.fPositionBuffer, "positions")
            if wireItem:
                self.setGeometryForRenderItem(wireItem, wireBuffers, self.fWireIndexBuffer, bounds)
            if selectItem:
                self.setGeometryForRenderItem(selectItem, wireBuffers, self.fWireIndexBuffer, bounds)

            boxBuffers = omr.MVertexBufferArray()
            boxBuffers.append(self.fBoxPositionBuffer, "positions")
            if boxItem:
                self.setGeometryForRenderItem(boxItem, boxBuffers, self.fBoxIndexBuffer, bounds)
            if selectedBoxItem:
                self.setGeometryForRenderItem(selectedBoxItem, boxBuffers, self.fBoxIndexBuffer, bounds)

            shadedBuffers = omr.MVertexBufferArray()
            shadedBuffers.append(self.fPositionBuffer, "positions")
            shadedBuffers.append(self.fNormalBuffer, "normals")
            self.setGeometryForRenderItem(shadedItem, shadedBuffers, self.fShadedIndexBuffer, bounds)
            self.setGeometryForRenderItem(texturedItem, shadedBuffers, self.fShadedIndexBuffer, bounds)

            # The vertexSelectionItem has a sequential index buffer, use non-indexed draw:
            self.setGeometryForRenderItem(vertexSelectionItem, wireBuffers, objectBox = bounds)
            self.setGeometryForRenderItem(edgeSelectionItem, wireBuffers, self.fWireIndexBuffer, bounds)
            self.setGeometryForRenderItem(faceSelectionItem, wireBuffers, self.fShadedIndexBuffer, bounds)

        ## Update active component items if required
        if itemsChanged or updateActiveItems:
            bounds = self.fMesh.boundingBox()

            vertexBuffer = omr.MVertexBufferArray()
            vertexBuffer.append(self.fPositionBuffer, "positions")

            if activeVertexItem:
                self.setGeometryForRenderItem(activeVertexItem, vertexBuffer, self.fActiveVerticesIndexBuffer, bounds)
            if activeEdgeItem:
                self.setGeometryForRenderItem(activeEdgeItem, vertexBuffer, self.fActiveEdgesIndexBuffer, bounds)
            if activeFaceItem:
                self.setGeometryForRenderItem(activeFaceItem, vertexBuffer, self.fActiveFacesIndexBuffer, bounds)

        ## Update render item matrices if necessary
        if itemsChanged or anyMatrixChanged:
            if not self.fIsInstanceMode and numInstances == 1:
                ## When not dealing with multiple instances, don't convert the render items into instanced
                ## mode.  Set the matrices on them directly.
                objToWorld = instanceMatrixArray[0]

                if wireItem:
                    wireItem.setMatrix(objToWorld)
                if selectItem:
                    selectItem.setMatrix(objToWorld)
                if boxItem:
                    boxItem.setMatrix(objToWorld)
                if selectedBoxItem:
                    selectedBoxItem.setMatrix(objToWorld)
                shadedItem.setMatrix(objToWorld)
                texturedItem.setMatrix(objToWorld)

                vertexSelectionItem.setMatrix(objToWorld)
                edgeSelectionItem.setMatrix(objToWorld)
                faceSelectionItem.setMatrix(objToWorld)

                if useDrawInstancingOnEdgeSelectionItem:
                    ## create/update draw instances
                    ## first instance : no scaling - won't be selectable see simpleComponentConverterSubsceneOverride.addIntersection
                    transform1 = objToWorld
                    transform1[15] = 1  # make sure we don't scale the w
                    ## second instance : scaled by 2
                    transform2 = objToWorld * 2
                    transform2[15] = 1  # make sure we don't scale the w
                    ## third instance : scaled by 3 - won't be selectable see simpleComponentConverterSubsceneOverride.addIntersection
                    transform3 = objToWorld * 3
                    transform3[15] = 1  # make sure we don't scale the w

                    if True:
                        transforms = om.MMatrixArray((transform1, transform2, transform3))
                        self.setInstanceTransformArray(edgeSelectionItem, transforms)
                    else:
                        ## another way to set up the instances
                        ## useful to get the instance ID
                        try:
                            self.removeAllInstances(edgeSelectionItem)
                        except:
                            # removeAllInstances raise an error if the item is not set up for instancing
                            pass
                        newInstanceId = self.addInstanceTransform(edgeSelectionItem, transform1)
                        print("newInstanceId " + str(newInstanceId))
                        newInstanceId = self.addInstanceTransform(edgeSelectionItem, transform2)
                        print("newInstanceId " + str(newInstanceId))
                        newInstanceId = self.addInstanceTransform(edgeSelectionItem, transform3)
                        print("newInstanceId " + str(newInstanceId))

                if activeVertexItem:
                    activeVertexItem.setMatrix(objToWorld)
                if activeEdgeItem:
                    activeEdgeItem.setMatrix(objToWorld)
                if activeFaceItem:
                    activeFaceItem.setMatrix(objToWorld)

            else:
                ## If we have DAG instances of this shape then use the MPxSubSceneOverride instance
                ## transform API to set up instance copies of the render items.  This will be faster
                ## to render than creating render items for each instance, especially for large numbers
                ## of instances.
                ## Note: for simplicity, this code is not tracking the actual shaded material binding
                ## of the shape.  MPxSubSceneOverride render item instances require that the shader
                ## and other properties of the instances all match.  So if we were to bind a shader based
                ## on the DAG shape material binding, then we would need one render item per material. We
                ## could then group up the instance transforms based matching materials.

                ## Note this has to happen after the geometry and shaders are set, otherwise it will fail.
                if wireItem:
                    self.setInstanceTransformArray(wireItem, unselectedInstanceMatrixArray)
                if selectItem:
                    self.setInstanceTransformArray(selectItem, selectedInstanceMatrixArray)
                if boxItem:
                    self.setInstanceTransformArray(boxItem, unselectedInstanceMatrixArray)
                if selectedBoxItem:
                    self.setInstanceTransformArray(selectedBoxItem, selectedInstanceMatrixArray)
                self.setInstanceTransformArray(shadedItem, instanceMatrixArray)
                self.setInstanceTransformArray(texturedItem, instanceMatrixArray)

                self.setInstanceTransformArray(vertexSelectionItem, instanceMatrixArray)
                self.setInstanceTransformArray(edgeSelectionItem, instanceMatrixArray)
                self.setInstanceTransformArray(faceSelectionItem, instanceMatrixArray)

                if activeVertexItem:
                    self.setInstanceTransformArray(activeVertexItem, instanceMatrixArray)
                if activeEdgeItem:
                    self.setInstanceTransformArray(activeEdgeItem, instanceMatrixArray)
                if activeFaceItem:
                    self.setInstanceTransformArray(activeFaceItem, instanceMatrixArray)

                ## Once we change the render items into instance rendering they can't be changed back without
                ## being deleted and re-created.  So if instances are deleted to leave only one remaining,
                ## just keep treating them the instance way.
                self.fIsInstanceMode = True
        
        self.manageIsolateSelectRenderItems(container, frameContext, instances, viewSelectedFaceInfo, shader, updateMaterial, updateGeometry)
        
        if itemsChanged or anyMatrixChanged or updateGeometry:
            ## On transform or geometry change, force recalculation of shadow maps
            omr.MRenderer.setLightsAndShadowsDirty()
    
    def manageIsolateSelectRenderItems(self, container, frameContext, instances, viewSelectedFaceInfo, shader, updateMaterial, updateGeometry):
        if (not self.fMesh):
            return
        
        meshGeom = self.fMesh.meshGeom()
        
        if (not meshGeom):
            return
        
        destination = frameContext.renderingDestination()
        if (destination[0] != omr.MFrameContext.k3dViewport):
            return
        
        ## Check whether the view-selected faces of the DAG instances changed for the current view
        activeViewName = destination[1]

        updateViewSelectedFaces = False

        if(activeViewName not in self.fViewSelectedFaceInfoCache):
            
            if(len(viewSelectedFaceInfo) != 0):
                updateViewSelectedFaces = True
                
        elif(self.fViewSelectedFaceInfoCache[activeViewName] != viewSelectedFaceInfo):
            updateViewSelectedFaces = True
        
        ##
        ##  Create/remove render items for the current view
        ##
        if updateViewSelectedFaces:
            
            ## Gather previous instances which own view-selected faces
            prevInstIdxArray = set()
            if (activeViewName in self.fViewSelectedFaceInfoCache):
                prevInfo = self.fViewSelectedFaceInfoCache[activeViewName]
                for instIdx, faceIdxList in list(prevInfo.items()):
                    for faceIdx in faceIdxList:
                        if faceIdx != sViewSelectedInstanceMark:
                            prevInstIdxArray.add(instIdx)
            
            ## Gather current instances which own view-selected faces
            currInstIdxArray = set()
            for instIdx, faceIdxList in list(viewSelectedFaceInfo.items()):
                for faceIdx in faceIdxList:
                    if (faceIdx != sViewSelectedInstanceMark):
                        currInstIdxArray.add(instIdx)
                        
            ## Update the cache now that we've gathered the previous data
            self.fViewSelectedFaceInfoCache[activeViewName] = viewSelectedFaceInfo
            
            ## For the DAG instances which don't own view-selected faces any more,
            ## their isolate select render items are removed to reduce the number of
            ## render items. Plug-ins can also choose to disable the render items if
            ## frequent reuse of the render items is expected.
            diffInstIdxArray = prevInstIdxArray - currInstIdxArray
            
            for instIdx in diffInstIdxArray:
                namePostfix = self.sNameSeparator + str(instIdx) + self.sNameSeparator + activeViewName
                
                shadedName = self.sShadedName + namePostfix
                container.remove(shadedName)
                
                texturedName = self.sTexturedName + namePostfix
                container.remove(texturedName)
                
                faceSelectionName = self.sFaceSelectionName + namePostfix
                container.remove(faceSelectionName)
                
            ## Create render items for new DAG instances which own view-selected
            ## faces since the last update
            for instIdx in currInstIdxArray:
                namePostfix = self.sNameSeparator + str(instIdx) + self.sNameSeparator + activeViewName
                
                shadedName = self.sShadedName + namePostfix
                viewSelectedShadedItem = container.find(shadedName)
                if not viewSelectedShadedItem:
                    
                    viewSelectedShadedItem = omr.MRenderItem.create(shadedName, omr.MRenderItem.MaterialSceneItem, omr.MGeometry.kTriangles)
                    viewSelectedShadedItem.setDrawMode(omr.MGeometry.kShaded)
                    viewSelectedShadedItem.setExcludedFromPostEffects(False)
                    viewSelectedShadedItem.setCastsShadows(True)
                    viewSelectedShadedItem.setReceivesShadows(True)
                    
                    container.add(viewSelectedShadedItem)

                    userData = apiMeshHWSelectionUserData()
                    userData.fMeshGeom = meshGeom
                    userData.fInstanceIndex = instIdx
                    viewSelectedShadedItem.setCustomData(userData)
                
                texturedName = self.sTexturedName + namePostfix
                viewSelectedTexturedItem = container.find(texturedName)
                if not viewSelectedTexturedItem:
                    
                    viewSelectedTexturedItem = omr.MRenderItem.create(texturedName, omr.MRenderItem.MaterialSceneItem, omr.MGeometry.kTriangles)

                    viewSelectedTexturedItem.setDrawMode(omr.MGeometry.kTextured)
                    viewSelectedTexturedItem.setExcludedFromPostEffects(False)
                    viewSelectedTexturedItem.setCastsShadows(True)
                    viewSelectedTexturedItem.setReceivesShadows(True)
                    container.add(viewSelectedTexturedItem)

                    userData = apiMeshHWSelectionUserData()
                    userData.fMeshGeom = meshGeom
                    userData.fInstanceIndex = instIdx
                    viewSelectedTexturedItem.setCustomData(userData)
                    
                faceSelectionName = self.sFaceSelectionName + namePostfix
                viewSelectedFaceSelectionItem = container.find(faceSelectionName)
                if not viewSelectedFaceSelectionItem:
                    
                    viewSelectedFaceSelectionItem = omr.MRenderItem.create(faceSelectionName, omr.MRenderItem.DecorationItem, omr.MGeometry.kTriangles)
                    
                    ## use for selection only : not visible in viewport
                    viewSelectedFaceSelectionItem.setDrawMode(omr.MGeometry.kSelectionOnly)
                    ## set the selection mask to kSelectMeshFaces : we want the render item to be used for Face Components selection
                    viewSelectedFaceSelectionItem.setSelectionMask(om.MSelectionMask.kSelectMeshFaces)
                    ## set selection priority : on top
                    viewSelectedFaceSelectionItem.setDepthPriority(omr.MRenderItem.sSelectionDepthPriority)
                    viewSelectedFaceSelectionItem.setShader(self.fFaceComponentShader)
                    container.add(viewSelectedFaceSelectionItem)
                
                    userData = apiMeshHWSelectionUserData()
                    userData.fMeshGeom = meshGeom
                    userData.fInstanceIndex = instIdx
                    viewSelectedFaceSelectionItem.setCustomData(userData)
                    
                    ## Register component converter for isolate select render items
                    if (faceSelectionName not in sViewSelectedFaceSelectionNames):
                        omr.MDrawRegistry.registerComponentConverter(faceSelectionName, simpleComponentConverterSubsceneOverride.creatorFaceSelection)
                        sViewSelectedFaceSelectionNames.add(faceSelectionName)
                
        ##
        ##  Update render items for all views as required
        ##
        for key in self.fViewSelectedFaceInfoCache:
            viewName = key
            faceInfo = self.fViewSelectedFaceInfoCache[key]
            isActiveView = viewName == activeViewName
            
            instIdxArray = set()
            for instIdx in faceInfo:
                faceIdx = faceInfo[instIdx]
                if (faceIdx != sViewSelectedInstanceMark):
                    instIdxArray.add(instIdx)
            
            for instIdx in instIdxArray:
                namePostfix = self.sNameSeparator + str(instIdx) + self.sNameSeparator + viewName
                
                viewSelectedShadedItem = container.find(self.sShadedName + namePostfix)
                viewSelectedTexturedItem = container.find(self.sTexturedName + namePostfix)
                viewSelectedFaceSelectionItem = container.find(self.sFaceSelectionName + namePostfix)
                if (not viewSelectedShadedItem or not viewSelectedTexturedItem or not viewSelectedFaceSelectionItem):
                    continue
                    
                ## Enable isolate select render items for the active view and disable those for other views
                viewSelectedShadedItem.enable(isActiveView)
                viewSelectedTexturedItem.enable(isActiveView)
                viewSelectedFaceSelectionItem.enable(isActiveView)
                
                ## Update matrix
                instance = instances[instIdx]
                objToWorld = instance.inclusiveMatrix()
                viewSelectedShadedItem.setMatrix(objToWorld)
                viewSelectedTexturedItem.setMatrix(objToWorld)
                viewSelectedFaceSelectionItem.setMatrix(objToWorld)
                
                ## Perform necessary update for shader, geometry, bounding box
                if (updateViewSelectedFaces or updateMaterial or updateGeometry):

                    if (updateMaterial or not viewSelectedShadedItem.isShaderFromNode()):
                        
                        userData = ShadedItemUserData(self)
                        
                        if shader and viewSelectedShadedItem.setShaderFromNode(shader, instance, apiMeshSubSceneOverride.shadedItemLinkLost, userData, True):
                            self.fLinkLostCallbackData.append(userData)
                        else:
                            viewSelectedShadedItem.setShader(self.fShadedShader)
                    
                    if (updateMaterial or not viewSelectedTexturedItem.isShaderFromNode()):
                        userData = ShadedItemUserData(self)
                        
                        if shader and viewSelectedTexturedItem.setShaderFromNode(shader, instance, apiMeshSubSceneOverride.shadedItemLinkLost, userData, True):
                            self.fLinkLostCallbackData.append(userData)
                        else:
                            viewSelectedTexturedItem.setShader(self.fShadedShader)
    
                    shadedBuffers = omr.MVertexBufferArray()
                    shadedBuffers.append(self.fPositionBuffer, "positions")
                    shadedBuffers.append(self.fNormalBuffer, "normals")
                    
                    selectionBuffers = omr.MVertexBufferArray()
                    selectionBuffers.append(self.fPositionBuffer, "positions")
                    
                    faceStates = []
                    for faceIdx in range(meshGeom.faceCount):
                        faceStates.append(False)
                    
                    faceIds = faceInfo[instIdx]
                    for faceIdx in faceIds:
                        if (faceIdx != sViewSelectedInstanceMark):
                            faceStates[faceIdx] = True
                    
                    numTriangles = 0
                    for faceIdx in range(meshGeom.faceCount):
                        numVerts = meshGeom.face_counts[faceIdx]
                        if (numVerts > 2):
                            if faceStates[faceIdx]:
                                numTriangles += numVerts - 2
                    
                    indexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
                    bufferSize = numTriangles * 3

                    dataAddress = indexBuffer.acquire(bufferSize, True)
                    if dataAddress:
                        data = (ctypes.c_uint * bufferSize).from_address(dataAddress)

                        base = 0
                        idx = 0
                        for faceIdx in range(meshGeom.faceCount):
                            ## Ignore degenerate faces
                            numVerts = meshGeom.face_counts[faceIdx]
                            if (numVerts > 2):
                                if (faceStates[faceIdx]):
                                    for v in range(1, numVerts - 1):
                                        data[idx] = meshGeom.face_connects[base]
                                        idx += 1
                                        data[idx] = meshGeom.face_connects[base + v]
                                        idx += 1
                                        data[idx] = meshGeom.face_connects[base + v + 1]
                                        idx += 1
                                base += numVerts
                        indexBuffer.commit(dataAddress)
                        dataAddress = None

                    bounds = self.fMesh.boundingBox()
                    self.setGeometryForRenderItem(viewSelectedShadedItem, shadedBuffers, indexBuffer, bounds)
                    self.setGeometryForRenderItem(viewSelectedTexturedItem, shadedBuffers, indexBuffer, bounds)
                    self.setGeometryForRenderItem(viewSelectedFaceSelectionItem, selectionBuffers, indexBuffer, bounds)
                    
                    ## The apiMeshGeom object can be re-created during DG evaluation, thus update the pointer.
                    userData = viewSelectedShadedItem.getCustomData()
                    if userData and isinstance(userData, apiMeshHWSelectionUserData):
                        userData.fMeshGeom = meshGeom
                        
                    userData = viewSelectedTexturedItem.getCustomData()
                    if userData and isinstance(userData, apiMeshHWSelectionUserData):
                        userData.fMeshGeom = meshGeom
                    
                    userData = viewSelectedFaceSelectionItem.getCustomData()
                    if userData and isinstance(userData, apiMeshHWSelectionUserData):
                        userData.fMeshGeom = meshGeom
                        userData.fFaceViewSelectedStates = faceStates
    
    def rebuildGeometryBuffers(self):
        ## Preamble
        meshGeom = self.fMesh.meshGeom()
        if not meshGeom:
            return
        bounds = self.fMesh.boundingBox()

        ## Clear old
        self.clearGeometryBuffers()

        ## Compute mesh data size
        numTriangles = 0
        totalVerts = 0
        totalPoints = len(meshGeom.vertices)
        for i in range(meshGeom.faceCount):
            numVerts = meshGeom.face_counts[i]
            if numVerts > 2:
                numTriangles += numVerts - 2
                totalVerts += numVerts

        ## Acquire vertex buffer resources
        posDesc = omr.MVertexBufferDescriptor("", omr.MGeometry.kPosition, omr.MGeometry.kFloat, 3)
        normalDesc = omr.MVertexBufferDescriptor("", omr.MGeometry.kNormal, omr.MGeometry.kFloat, 3)

        self.fPositionBuffer = omr.MVertexBuffer(posDesc)
        self.fNormalBuffer = omr.MVertexBuffer(normalDesc)
        self.fBoxPositionBuffer = omr.MVertexBuffer(posDesc)

        positionDataAddress = self.fPositionBuffer.acquire(totalPoints, True)
        normalDataAddress = self.fNormalBuffer.acquire(totalPoints, True)
        boxPositionDataAddress = self.fBoxPositionBuffer.acquire(8, True)

        ## Acquire index buffer resources
        self.fWireIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
        self.fBoxIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
        self.fShadedIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)

        wireBufferDataAddress = self.fWireIndexBuffer.acquire(2*totalVerts, True)
        boxBufferDataAddress = self.fBoxIndexBuffer.acquire(24, True)
        shadedBufferDataAddress = self.fShadedIndexBuffer.acquire(3*numTriangles, True)

        ## Sanity check
        if not all((positionDataAddress, normalDataAddress, boxPositionDataAddress, wireBufferDataAddress, boxBufferDataAddress, shadedBufferDataAddress)):
            self.clearGeometryBuffers()
            return

        positionData = ((ctypes.c_float * 3)*totalPoints).from_address(positionDataAddress)
        normalData = ((ctypes.c_float * 3)*totalPoints).from_address(normalDataAddress)
        boxPositionData = ((ctypes.c_float * 3)*8).from_address(boxPositionDataAddress)

        wireBufferData = (ctypes.c_uint * (2*totalVerts)).from_address(wireBufferDataAddress)
        boxBufferData = (ctypes.c_uint * 24).from_address(boxBufferDataAddress)
        shadedBufferData = ((ctypes.c_uint * 3)*numTriangles).from_address(shadedBufferDataAddress)

        ## Fill vertex data for shaded/wireframe
        for vid,position in enumerate(meshGeom.vertices):
            positionData[vid][0] = position[0]
            positionData[vid][1] = position[1]
            positionData[vid][2] = position[2]

        for vid,normal in enumerate(meshGeom.normals):
            normalData[vid][0] = normal[0]
            normalData[vid][1] = normal[1]
            normalData[vid][2] = normal[2]

        self.fPositionBuffer.commit(positionDataAddress)
        positionDataAddress = None
        self.fNormalBuffer.commit(normalDataAddress)
        normalDataAddress = None

        ## Fill vertex data for bounding box
        bbmin = bounds.min
        bbmax = bounds.max
        boxPositionData[0][0] = bbmin.x
        boxPositionData[0][1] = bbmin.y
        boxPositionData[0][2] = bbmin.z

        boxPositionData[1][0] = bbmin.x
        boxPositionData[1][1] = bbmin.y
        boxPositionData[1][2] = bbmax.z

        boxPositionData[2][0] = bbmax.x
        boxPositionData[2][1] = bbmin.y
        boxPositionData[2][2] = bbmax.z

        boxPositionData[3][0] = bbmax.x
        boxPositionData[3][1] = bbmin.y
        boxPositionData[3][2] = bbmin.z

        boxPositionData[4][0] = bbmin.x
        boxPositionData[4][1] = bbmax.y
        boxPositionData[4][2] = bbmin.z

        boxPositionData[5][0] = bbmin.x
        boxPositionData[5][1] = bbmax.y
        boxPositionData[5][2] = bbmax.z

        boxPositionData[6][0] = bbmax.x
        boxPositionData[6][1] = bbmax.y
        boxPositionData[6][2] = bbmax.z

        boxPositionData[7][0] = bbmax.x
        boxPositionData[7][1] = bbmax.y
        boxPositionData[7][2] = bbmin.z

        self.fBoxPositionBuffer.commit(boxPositionDataAddress)
        boxPositionDataAddress = None

        ## Fill index data for wireframe
        vid = 0
        first = 0
        idx = 0
        for i in range(meshGeom.faceCount):
            ## Ignore degenerate faces
            numVerts = meshGeom.face_counts[i]
            if numVerts > 2:
                first = vid
                for v in range(numVerts-1):
                    wireBufferData[idx] = meshGeom.face_connects[vid]
                    idx += 1
                    vid += 1
                    wireBufferData[idx] = meshGeom.face_connects[vid]
                    idx += 1

                wireBufferData[idx] = meshGeom.face_connects[vid]
                idx += 1
                vid += 1
                wireBufferData[idx] = meshGeom.face_connects[first]
                idx += 1

            else:
                vid += numVerts

        self.fWireIndexBuffer.commit(wireBufferDataAddress)
        wireBufferDataAddress = None

        ## Fill index data for bounding box
        indexData = [ 0, 1, 1, 2, 2, 3, 3, 0, 4, 5, 5, 6, 6, 7, 7, 4, 0, 4, 1, 5, 2, 6, 3, 7 ]
        for i in range(24):
            boxBufferData[i] = indexData[i]

        self.fBoxIndexBuffer.commit(boxBufferDataAddress)
        boxBufferDataAddress = None

        ## Fill index data for shaded
        base = 0
        idx = 0
        for i in range(meshGeom.faceCount):
            ## Ignore degenerate faces
            numVerts = meshGeom.face_counts[i]
            if numVerts > 2:
                for v in range(1, numVerts-1):
                    shadedBufferData[idx][0] = meshGeom.face_connects[base]
                    shadedBufferData[idx][1] = meshGeom.face_connects[base+v]
                    shadedBufferData[idx][2] = meshGeom.face_connects[base+v+1]
                    idx += 1

                base += numVerts
        
        self.fShadedIndexBuffer.commit(shadedBufferDataAddress)
        shadedBufferDataAddress = None

    def rebuildActiveComponentIndexBuffers(self):
        ## Preamble
        meshGeom = self.fMesh.meshGeom()
        if not meshGeom:
            return

        ## Clear old
        self.clearActiveComponentIndexBuffers()

        ## Acquire and fill index buffer for active vertices
        numActiveVertices = len(self.fActiveVerticesSet)
        if numActiveVertices > 0:
            self.fActiveVerticesIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
            activeVerticesDataAddress = self.fActiveVerticesIndexBuffer.acquire(numActiveVertices, True)
            if activeVerticesDataAddress:
                activeVerticesData = (ctypes.c_uint*numActiveVertices).from_address(activeVerticesDataAddress)

                idx = 0
                for vid in self.fActiveVerticesSet:
                    activeVerticesData[idx] = vid 
                    idx += 1

                self.fActiveVerticesIndexBuffer.commit(activeVerticesDataAddress)
                activeVerticesDataAddress = None

        ## Acquire and fill index buffer for active edges
        numActiveEdges = len(self.fActiveEdgesSet)
        if numActiveEdges > 0:
            self.fActiveEdgesIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
            activeEdgesDataAddress = self.fActiveEdgesIndexBuffer.acquire(2*numActiveEdges, True)
            if activeEdgesDataAddress:
                activeEdgesData = ((ctypes.c_uint * 2)*numActiveEdges).from_address(activeEdgesDataAddress)

                eid = 0
                first = 0
                vid = 0
                idx = 0
                for i in range(meshGeom.faceCount):
                    ## Ignore degenerate faces
                    numVerts = meshGeom.face_counts[i]
                    if numVerts > 2:
                        first = vid
                        for v in range(numVerts-1):
                            if eid in self.fActiveEdgesSet:
                                activeEdgesData[idx][0] = meshGeom.face_connects[vid]
                                activeEdgesData[idx][1] = meshGeom.face_connects[vid + 1]
                                idx += 1
                            vid += 1
                            eid += 1

                        if eid in self.fActiveEdgesSet:
                            activeEdgesData[idx][0] = meshGeom.face_connects[vid]
                            activeEdgesData[idx][1] = meshGeom.face_connects[first]
                            idx += 1
                        vid += 1
                        eid += 1
                    else:
                        vid += numVerts

                self.fActiveEdgesIndexBuffer.commit(activeEdgesDataAddress)
                activeEdgesDataAddress = None

        ## Acquire and fill index buffer for active faces
        numActiveFaces = len(self.fActiveFacesSet)
        if numActiveFaces > 0:
            numActiveFacesTriangles = 0
            for i in range(meshGeom.faceCount):
                if i in self.fActiveFacesSet:
                    numVerts = meshGeom.face_counts[i]
                    if numVerts > 2:
                        numActiveFacesTriangles += numVerts - 2

            self.fActiveFacesIndexBuffer = omr.MIndexBuffer(omr.MGeometry.kUnsignedInt32)
            activeFacesDataAddress = self.fActiveFacesIndexBuffer.acquire(3*numActiveFacesTriangles, True)
            if activeFacesDataAddress:
                activeFacesData = ((ctypes.c_uint * 3)*numActiveFacesTriangles).from_address(activeFacesDataAddress)

                idx = 0
                vid = 0
                for i in range(meshGeom.faceCount):
                    numVerts = meshGeom.face_counts[i]
                    if numVerts > 2:
                        if i in self.fActiveFacesSet:
                            for v in range(1, numVerts-1):
                                activeFacesData[idx][0] = meshGeom.face_connects[vid]
                                activeFacesData[idx][1] = meshGeom.face_connects[vid+v]
                                activeFacesData[idx][2] = meshGeom.face_connects[vid+v+1]
                                idx += 1

                        vid += numVerts

                self.fActiveFacesIndexBuffer.commit(activeFacesDataAddress)
                activeFacesDataAddress = None

    def clearBuffers(self):
        self.clearGeometryBuffers()
        self.clearActiveComponentIndexBuffers()

    def clearGeometryBuffers(self):
        self.fPositionBuffer = None
        self.fNormalBuffer = None
        self.fBoxPositionBuffer = None
        self.fWireIndexBuffer = None
        self.fBoxIndexBuffer = None
        self.fShadedIndexBuffer = None

    def clearActiveComponentIndexBuffers(self):
        self.fActiveVerticesIndexBuffer = None
        self.fActiveEdgesIndexBuffer = None
        self.fActiveFacesIndexBuffer = None

    def updateSelectionGranularity(self, path, selectionContext):
        ## This is method is called during the pre-filtering phase of the viewport 2.0 selection
        ## and is used to setup the selection context of the given DAG object.

        ## We want the whole shape to be selectable, so we set the selection level to kObject so that the shape
        ## will be processed by the selection.

        ## In case we are currently in component selection mode (vertex, edge or face),
        ## since we have created render items that can be use in the selection phase (kSelectionOnly draw mode)
        ## and we also registered component converters to handle this render items,
        ## we can set the selection level to kComponent so that the shape will also be processed by the selection.
        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        if displayStatus == omr.MGeometryUtilities.kHilite:
    
            globalComponentMask = om.MGlobal.objectSelectionMask()
            if om.MGlobal.selectionMode() == om.MGlobal.kSelectComponentMode:
                globalComponentMask = om.MGlobal.componentSelectionMask()

            supportedComponentMask = om.MSelectionMask( om.MSelectionMask.kSelectMeshVerts )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectMeshEdges )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectMeshFaces )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectPointsForGravity )
            
            if globalComponentMask.intersects(supportedComponentMask):
                selectionContext.selectionLevel = omr.MSelectionContext.kComponent
        elif omr.MPxSubSceneOverride.pointSnappingActive():
            selectionContext.selectionLevel = omr.MSelectionContext.kComponent
            
    def getSelectionPath(self, renderItem, dagPath):
        node = om.MFnDagNode(self.fObject)
        if not node:
            return False
            
        instances = node.getAllPaths()
        if not instances or len(instances) == 0:
            return False
        
        dagPath.set(instances[0])
        return True
        
    def getInstancedSelectionPath(self, renderItem, intersection, dagPath):
        node = om.MFnDagNode(self.fObject)
        if not node:
            return False
        
        instances = node.getAllPaths()
        instanceCount = len(instances)
        if not instances or instanceCount == 0:
            return False
        
        instanceId = intersection.instanceID
        
        ## In case there is only one instance or GPU instancing is not used
        if(instanceCount == 1 or instanceId == -1):
            instanceId = 0
            userData = renderItem.getCustomData()
            if( userData and 
                isinstance(userData, apiMeshHWSelectionUserData) and 
                userData.fInstanceIndex >= 0 and 
                userData.fInstanceIndex < instanceCount):
                instanceId = userData.fInstanceIndex

            dagPath.set(instances[instanceId])
            return True
        ## The instance ID starts from 1 for the first DAG node. We can use instanceID - 1  
        ## as the index to DagPath array returned by MFnDagNode::getAllPaths().
        ## HOWEVER there is an exception when there are instances within a Shape object,
        ## which introduces nested instancing scenarios. For simplicity reason the selection
        ## edge instancing is disabled when there are multiple apiMesh instances.
        elif(instanceId >=1 and instanceId <= instanceCount):
            view = omui.M3dView.active3dView()
            if view.viewIsFiltered():
                
                viewSelectedList = view.filteredObjectList()
                if viewSelectedList:
                    for instIdx in range(instanceCount):
                        instance = instances[instIdx]
                        if instance.isValid() and instance.isVisible():
                            intersectionList = om.MSelectionList()
                            
                            intersectionList.add(instance)
                            intersectionList.intersect(viewSelectedList, True)
                            
                            selectionIt = om.MItSelectionList(intersectionList)
                            while not selectionIt.isDone():
                                comp = selectionIt.getComponent()[1]
                                
                                if not comp:
                                    instanceId = instanceId - 1
                                    if instanceId == 0:
                                        dagPath.set(instance)
                                        return True
                                next(selectionIt)
            else:               
                for instIdx in range(instanceCount):
                    instance = instances[instIdx]
                    if (instance.isValid() and instance.isVisible()):
                        instanceId = instanceId - 1
                        if (instanceId == 0):
                            dagPath.set(instance)
                            return True
                            
        return False
    
################################################################################
##
## apiMeshGeometryOverride
##
## Handles vertex data preparation for drawing the user defined shape in
## Viewport 2.0.
##
################################################################################
## Custom user data class to attach to render items
class apiMeshUserData(om.MUserData):
    def __init__(self):
        om.MUserData.__init__(self, True)   ## let Maya clean up
        self.fMessage = ""
        self.fNumModifications = 0

## Pre/Post callback helper
def callbackDataPrint(context, renderItemList):
    for item in renderItemList:
        if item:
            path = item.sourceDagPath()
            print("\tITEM: '" + item.name() + "' -- SOURCE: '" + path.fullPathName() + "'")

    passCtx = context.getPassContext()
    passId = passCtx.passIdentifier()
    passSem = passCtx.passSemantics()
    print("\tAPI mesh drawing in pass[" + passId + "], semantic[" + passSem + "]")

## Custom pre-draw callback
def apiMeshPreDrawCallback(context, renderItemList, shaderInstance):
    print("PRE-draw callback triggered for render item list with data:")
    callbackDataPrint(context, renderItemList)

## Custom post-draw callback
def apiMeshPostDrawCallback(context, renderItemList, shaderInstance):
    print("POST-draw callback triggered for render item list with data:")
    callbackDataPrint(context, renderItemList)

## Custom component converter to select vertices
## Attached to the dormant vertices render item (apiMeshGeometryOverride.sVertexItemName)
class meshVertComponentConverterGeometryOverride(omr.MPxComponentConverter):
    def __init__(self):
        omr.MPxComponentConverter.__init__(self)

        self.fComponent = om.MFnSingleIndexedComponent()
        self.fComponentObject = om.MObject.kNullObj
        self.fVertices = []

    def initialize(self, renderItem):
        ## Create the component selection object .. here we are selecting vertex component
        self.fComponentObject = self.fComponent.create( om.MFn.kMeshVertComponent )

        ## Build a lookup table to match each primitive position in the index buffer of the render item geometry
        ## to the correponding vertex component of the object
        ## Use same algorithm as in apiMeshGeometryOverride.updateIndexingForDormantVertices

        selectionData = renderItem.getCustomData()
        if isinstance(selectionData, apiMeshHWSelectionUserData):
            meshGeom = selectionData.fMeshGeom

            ## Allocate vertices lookup table
            numTriangles = 0
            for i in range(meshGeom.faceCount):
                numVerts = meshGeom.face_counts[i]
                if numVerts > 2:
                    numTriangles += numVerts - 2
            self.fVertices = [0]*(3*numTriangles)

            ## Fill vertices lookup table
            base = 0
            idx = 0
            for faceIdx in range(meshGeom.faceCount):
                ## ignore degenerate faces
                numVerts = meshGeom.face_counts[faceIdx]
                if numVerts > 2:
                    for v in range(1, numVerts-1):
                        self.fVertices[idx] = meshGeom.face_connects[base]
                        self.fVertices[idx+1] = meshGeom.face_connects[base+v]
                        self.fVertices[idx+2] = meshGeom.face_connects[base+v+1]
                        idx += 3
                    base += numVerts

    def addIntersection(self, intersection):
        ## Convert the intersection index, which represent the primitive position in the
        ## index buffer, to the correct vertex component
        rawIdx = intersection.index
        idx = 0
        if rawIdx >= 0 and rawIdx < len(self.fVertices):
            idx = self.fVertices[rawIdx]
        self.fComponent.addElement(idx)

    def component(self):
        ## Return the component object that contains the ids of the selected vertices
        return self.fComponentObject

    def selectionMask(self):
        ## This converter is only valid for vertex selection
        mask = om.MSelectionMask(om.MSelectionMask.kSelectMeshVerts)
        mask.addMask(om.MSelectionMask.kSelectPointsForGravity)
        return mask

    @staticmethod
    def creator():
        return meshVertComponentConverterGeometryOverride()

## Custom component converter to select edges
## Attached to the edge selection render item (apiMeshGeometryOverride.sEdgeSelectionItemName)
class meshEdgeComponentConverterGeometryOverride(omr.MPxComponentConverter):
    def __init__(self):
        omr.MPxComponentConverter.__init__(self)

        self.fComponent = om.MFnSingleIndexedComponent()
        self.fComponentObject = om.MObject.kNullObj
        self.fEdges = []

    def initialize(self, renderItem):
        ## Create the component selection object .. here we are selecting edge component
        self.fComponentObject = self.fComponent.create( om.MFn.kMeshEdgeComponent )

        ## Build a lookup table to match each primitive position in the index buffer of the render item geometry
        ## to the correponding edge component of the object
        ## Use same algorithm as in apiMeshGeometryOverride.updateIndexingForEdges

        ## in updateIndexingForEdges the index buffer is allocated with "totalEdges = 2*totalVerts"
        ## but since we are drawing lines, we'll get only half of the data as primitive positions :
        ## indices 0 & 1 : primitive #0
        ## indices 2 & 3 : primitive #1
        ## ...

        selectionData = renderItem.getCustomData()
        if isinstance(selectionData, apiMeshHWSelectionUserData):
            meshGeom = selectionData.fMeshGeom

            ## Allocate edges lookup table
            totalVerts = 0
            for i in range(meshGeom.faceCount):
                numVerts = meshGeom.face_counts[i]
                if numVerts > 2:
                    totalVerts += numVerts
            self.fEdges = [0]*(totalVerts)

            ## Fill edges lookup table
            idx = 0
            edgeId = 0
            for faceIdx in range(meshGeom.faceCount):
                ## ignore degenerate faces
                numVerts = meshGeom.face_counts[faceIdx]
                if numVerts > 2:
                    for v in range(numVerts):
                        self.fEdges[idx] = edgeId
                        edgeId += 1
                        idx += 1

    def addIntersection(self, intersection):
        ## Convert the intersection index, which represent the primitive position in the
        ## index buffer, to the correct edge component
        rawIdx = intersection.index
        idx = 0
        if rawIdx >= 0 and rawIdx < len(self.fEdges):
            idx = self.fEdges[rawIdx]
        self.fComponent.addElement(idx)

    def component(self):
        ## Return the component object that contains the ids of the selected edges
        return self.fComponentObject

    def selectionMask(self):
        ## This converter is only valid for edge selection
        return om.MSelectionMask(om.MSelectionMask.kSelectMeshEdges)

    @staticmethod
    def creator():
        return meshEdgeComponentConverterGeometryOverride()

## Custom component converter to select faces
## Attached to the face selection render item (apiMeshGeometryOverride.sFaceSelectionItemName)
class meshFaceComponentConverterGeometryOverride(omr.MPxComponentConverter):
    def __init__(self):
        omr.MPxComponentConverter.__init__(self)

        self.fComponent = om.MFnSingleIndexedComponent()
        self.fComponentObject = om.MObject.kNullObj
        self.fFaces = []

    def initialize(self, renderItem):
        ## Create the component selection object .. here we are selecting face component
        self.fComponentObject = self.fComponent.create( om.MFn.kMeshPolygonComponent )

        ## Build a lookup table to match each primitive position in the index buffer of the render item geometry
        ## to the correponding face component of the object
        ## Use same algorithm as in apiMeshGeometryOverride.updateIndexingForFaces

        ## in updateIndexingForFaces the index buffer is allocated with "numTriangleVertices = 3*numTriangles"
        ## but since we are drawing triangles, we'll get only a third of the data as primitive positions :
        ## indices 0, 1 & 2 : primitive #0
        ## indices 3, 4 & 5 : primitive #1
        ## ...

        selectionData = renderItem.getCustomData()
        if isinstance(selectionData, apiMeshHWSelectionUserData):
            meshGeom = selectionData.fMeshGeom

            ## isolate selection
            isolateSelect = renderItem.isIsolateSelectCopy()
            if(isolateSelect):
                
                enableFaces = [0] * meshGeom.faceCount
                for i in range(meshGeom.faceCount):
                    enableFaces[i] = False

                fnComponent = om.MFnSingleIndexedComponent( renderItem.shadingComponent() )
                if(fnComponent.componentType == om.MFn.kMeshPolygonComponent):
                    faceIds = fnComponent.getElements()
                    
                    for i in range(len(faceIds)):
                        enableFaces[faceIds[i]] = True

            ## Allocate faces lookup table
            numTriangles = 0
            for i in range(meshGeom.faceCount):
                numVerts = meshGeom.face_counts[i]
                if numVerts > 2:
                    if(not isolateSelect or enableFaces[i]):
                        numTriangles += numVerts - 2

            self.fFaces = [0]*numTriangles

            ## Fill faces lookup table
            idx = 0
            for faceIdx in range(meshGeom.faceCount):
                ## ignore degenerate faces
                numVerts = meshGeom.face_counts[faceIdx]
                if numVerts > 2:
                    if(not isolateSelect or enableFaces[faceIdx]):
                        for v in range(1, numVerts-1):
                            self.fFaces[idx] = faceIdx
                            idx += 1



    def addIntersection(self, intersection):
        ## Convert the intersection index, which represent the primitive position in the
        ## index buffer, to the correct face component
        rawIdx = intersection.index
        idx = 0
        if rawIdx >= 0 and rawIdx < len(self.fFaces):
            idx = self.fFaces[rawIdx]
        self.fComponent.addElement(idx)

    def component(self):
        ## Return the component object that contains the ids of the selected faces
        return self.fComponentObject

    def selectionMask(self):
        ## This converter is only valid for face selection
        return om.MSelectionMask(om.MSelectionMask.kSelectMeshFaces)

    @staticmethod
    def creator():
        return meshFaceComponentConverterGeometryOverride()

class apiMeshGeometryOverride(omr.MPxGeometryOverride):
    ## Render item names
    sWireframeItemName = "apiMeshWire_py"
    sShadedTemplateItemName = "apiMeshShadedTemplateWire_py"
    sSelectedWireframeItemName = "apiMeshSelectedWireFrame_py"
    sVertexItemName = "apiMeshVertices_py"
    sEdgeSelectionItemName = "apiMeshEdgeSelection_py"
    sFaceSelectionItemName = "apiMeshFaceSelection_py"
    sActiveVertexItemName = "apiMeshActiveVertices_py"
    sVertexIdItemName = "apiMeshVertexIds_py"
    sVertexPositionItemName = "apiMeshVertexPositions_py"
    sShadedModeFaceCenterItemName = "apiMeshFaceCenterInShadedMode_py"
    sWireframeModeFaceCenterItemName = "apiMeshFaceCenterInWireframeMode_py"
    sShadedProxyItemName = "apiShadedProxy_py"
    sAffectedEdgeItemName = "apiMeshAffectedEdges_py"
    sAffectedFaceItemName = "apiMeshAffectedFaces_py"
    sActiveVertexStreamName = "apiMeshSharedVertexStream_py"
    sFaceCenterStreamName = "apiMeshFaceCenterStream_py"

    @staticmethod
    def creator(obj):
        return apiMeshGeometryOverride(obj)

    def __init__(self, obj):
        omr.MPxGeometryOverride.__init__(self, obj)

        node = om.MFnDependencyNode(obj)
        self.fMesh = node.userNode()
        self.fMeshGeom = None
        self.fColorRemapTexture = None

        self.fActiveVertices = om.MIntArray()
        self.fActiveVerticesSet = set()
        self.fActiveEdgesSet = set()
        self.fActiveFacesSet = set()
        self.fCastsShadows = False
        self.fReceivesShadows = False
        ## Enable to show numeric render items
        self.fEnableNumericDisplay = False

        ## Stream names used for filling in different data
        ## for different streams required for different render items,
        ## and toggle to choose whether to use name streams
        ##
        self.fDrawSharedActiveVertices = True
        ## Turn on to view active vertices with colours lookedup from a 1D texture.
        self.fDrawActiveVerticesWithRamp = False
        self.fLinearSampler = None

        ##Vertex stream for face centers which is calculated from faces.
        self.fDrawFaceCenters = True

        if self.fDrawActiveVerticesWithRamp:
            self.fDrawFaceCenters = False   ## Too cluttered showing the face centers at the same time.

        ## Can set the following to True, but then the logic to
        ## determine what color to set is the responsibility of the plugin.
        ##
        self.fUseCustomColors = False

        ## Can change this to choose a different shader to use when
        ## no shader node is assigned to the object.
        ## self.fProxyShader = omr.MShaderManager.k3dSolidShader ## - Basic line shader
        ## self.fProxyShader = omr.MShaderManager.k3dStippleShader ## - For filled stipple faces (triangles)
        ## self.fProxyShader = omr.MShaderManager.k3dThickLineShader ## For thick solid colored lines
        ## self.fProxyShader = omr.MShaderManager.k3dCPVThickLineShader ## For thick colored lines. Black if no CPV
        ## self.fProxyShader = omr.MShaderManager.k3dDashLineShader ## - For dashed solid color lines
        ## self.fProxyShader = omr.MShaderManager.k3dCPVDashLineShader ##- For dashed coloured lines. Black if no CPV
        ## self.fProxyShader = omr.MShaderManager.k3dThickDashLineShader ## For thick dashed solid color lines. black if no cpv
        self.fProxyShader = omr.MShaderManager.k3dCPVThickDashLineShader ##- For thick, dashed and coloured lines

        ## Set to True to test that overriding internal items has no effect
        ## for shadows and effects overrides
        self.fInternalItems_NoShadowCast = False
        self.fInternalItems_NoShadowReceive = False
        self.fInternalItems_NoPostEffects = False

        ## Use the existing shadow casts / receives flags on the shape
        ## to drive settings for applicable render items.
        self.fExternalItems_NoShadowCast = False
        self.fExternalItems_NoShadowReceive = False
        self.fExternalItemsNonTri_NoShadowCast = False
        self.fExternalItemsNonTri_NoShadowReceive = False

        ## Set to True to ignore post-effects for wireframe items.
        ## Shaded items will still have effects applied.
        self.fExternalItems_NoPostEffects = True
        self.fExternalItemsNonTri_NoPostEffects = True

    def __del__(self):
        self.fMesh = None
        self.fMeshGeom = None

        if self.fColorRemapTexture:
            textureMgr = omr.MRenderer.getTextureManager()
            if textureMgr:
                textureMgr.releaseTexture(self.fColorRemapTexture)
            self.fColorRemapTexture = None

        if self.fLinearSampler:
            omr.MStateManager.releaseSamplerState(self.fLinearSampler)
            self.fLinearSampler = None

    def supportedDrawAPIs(self):
        ## this plugin supports both GL and DX
        return omr.MRenderer.kOpenGL | omr.MRenderer.kDirectX11 | omr.MRenderer.kOpenGLCoreProfile

    def updateDG(self):
        ## Pull the actual outMesh from the shape, as well
        ## as any active components
        self.fActiveVertices.clear()
        self.fActiveVerticesSet = set()
        self.fActiveEdgesSet = set()
        self.fActiveFacesSet = set()
        if self.fMesh:
            self.fMeshGeom = self.fMesh.meshGeom()

            if self.fMeshGeom and self.fMesh.hasActiveComponents():
                activeComponents = self.fMesh.activeComponents()
                if len(activeComponents) > 0:
                    fnComponent = om.MFnSingleIndexedComponent( activeComponents[0] )
                    if fnComponent.elementCount > 0:
                        activeIds = fnComponent.getElements()

                        if fnComponent.componentType == om.MFn.kMeshVertComponent:
                            self.fActiveVertices = activeIds
                            self.fActiveVerticesSet = set(activeIds)

                        elif fnComponent.componentType == om.MFn.kMeshEdgeComponent:
                            self.fActiveEdgesSet = set(activeIds)

                        elif fnComponent.componentType == om.MFn.kMeshPolygonComponent:
                            self.fActiveFacesSet = set(activeIds)

    def updateRenderItems(self, path, list):
        ## Update render items. Shaded render item is provided so this
        ## method will be adding and updating UI render items only.

        shaderMgr = omr.MRenderer.getShaderManager()
        if not shaderMgr:
            return

        dagNode = om.MFnDagNode(path)
        castsShadowsPlug = dagNode.findPlug("castsShadows", False)
        self.fCastsShadows = castsShadowsPlug.asBool()
        receiveShadowsPlug = dagNode.findPlug("receiveShadows", False)
        self.fReceivesShadows = receiveShadowsPlug.asBool()
        enableNumericDisplayPlug = dagNode.findPlug("enableNumericDisplay", False)
        self.fEnableNumericDisplay = enableNumericDisplayPlug.asBool()

        ##1 Update wireframe render items
        self.updateDormantAndTemplateWireframeItems(path, list, shaderMgr)
        self.updateActiveWireframeItem(path, list, shaderMgr)

        ## Update vertex render items
        self.updateDormantVerticesItem(path, list, shaderMgr)
        self.updateActiveVerticesItem(path, list, shaderMgr)

        ## Update vertex numeric render items
        self.updateVertexNumericItems(path, list, shaderMgr)

        ## Update face center item
        if self.fDrawFaceCenters:
            self.updateWireframeModeFaceCenterItem(path, list, shaderMgr)
            self.updateShadedModeFaceCenterItem(path, list, shaderMgr)

        ## Update "affected" edge and face render items
        self.updateAffectedComponentItems(path, list, shaderMgr)

        ## Update faces and edges selection items
        self.updateSelectionComponentItems(path, list, shaderMgr)

        ## Update proxy shaded render item
        self.updateProxyShadedItem(path, list, shaderMgr)

        ## Test overrides on existing shaded items.
        ## In this case it is not valid to override these states
        ## so there should be no change in behaviour.
        ##
        testShadedOverrides = self.fInternalItems_NoShadowCast or self.fInternalItems_NoShadowReceive or self.fInternalItems_NoPostEffects
        if testShadedOverrides:
            for item in list:
                if not item:
                    continue

                drawMode = item.drawMode()
                if drawMode == omr.MGeometry.kShaded or drawMode == omr.MGeometry.kTextured:
                    if item.name() != self.sShadedTemplateItemName:
                        item.setCastsShadows( not self.fInternalItems_NoShadowCast and self.fCastsShadows )
                        item.setReceivesShadows( not self.fInternalItems_NoShadowReceive and self.fReceivesShadows )
                        item.setExcludedFromPostEffects( self.fInternalItems_NoPostEffects )

    def populateGeometry(self, requirements, renderItems, data):
        ## Fill in data and index streams based on the requirements passed in.
        ## Associate indexing with the render items passed in.
        ## 
        ## Note that we leave both code paths to either draw shared or non-shared active vertices.
        ## The choice of which to use is up to the circumstances per plug-in.
        ## When drawing shared vertices, this requires an additional position buffer to be
        ## created so will use more memory. If drawing unshared vertices redundent extra
        ## vertices are drawn but will use less memory. The data member fDrawSharedActiveVertices
        ## can be set to decide on which implementation to use.

        debugPopulateGeometry = False
        if debugPopulateGeometry:
            print("> Begin populate geometry")

        ## Get the active vertex count
        activeVertexCount = len(self.fActiveVertices)

        ## Compute the number of triangles, assume polys are always convex
        numTriangles = 0
        totalVerts = 0
        for i in range(self.fMeshGeom.faceCount):
            numVerts = self.fMeshGeom.face_counts[i]
            if numVerts > 2:
                numTriangles += numVerts - 2
                totalVerts += numVerts

        ## Update data streams based on geometry requirements
        self.updateGeometryRequirements(requirements, data, activeVertexCount, totalVerts, debugPopulateGeometry)

        ## Update indexing data for all appropriate render items
        wireIndexBuffer = None ## reuse same index buffer for both wireframe and selected

        for item in renderItems:
            if not item:
                continue

            ## Enable to debug vertex buffers that are associated with each render item.
            ## Can also use to generate indexing better, but we don't need that here.
            ## Also debugs custom data on the render item.
            debugStuff = False
            if debugStuff:
                itemBuffers = item.requiredVertexBuffers()
                for desc in itemBuffers:
                    print("Buffer Required for Item '" + item.name() + "':")
                    print("\tBufferName: " + desc.name)
                    print("\tDataType: " + omr.MGeometry.dataTypeString(desc.dataType) + " (dimension " + str(desc.dimension) + ")")
                    print("\tSemantic: " + omr.MGeometry.semanticString(desc.semantic))
                    print("")

                ## Just print a message for illustration purposes. Note that the custom data is also
                ## accessible from the MRenderItem in MPxShaderOverride::draw().
                myCustomData = item.getCustomData()
                if isinstance(myCustomData, apiMeshUserData):
                    print("Custom data '" + myCustomData.fMessage + "', modified count='" + str(myCustomData.fNumModifications) + "'")
                else:
                    print("No custom data")

            ## Update indexing for active vertex item
            ##
            if item.name() == self.sActiveVertexItemName:
                self.updateIndexingForVertices( item, data, numTriangles, activeVertexCount, debugPopulateGeometry)

            ## Update indexing for face center item in wireframe mode and shaded mode
            ##
            if self.fDrawFaceCenters and (item.name() == self.sShadedModeFaceCenterItemName or item.name() == self.sWireframeModeFaceCenterItemName):
                self.updateIndexingForFaceCenters( item, data, debugPopulateGeometry)

            ## Create indexing for dormant and numeric vertex render items
            ##
            elif item.name() == self.sVertexItemName or item.name() == self.sVertexIdItemName or item.name() == self.sVertexPositionItemName:
                self.updateIndexingForDormantVertices( item, data, numTriangles )

            ## Create indexing for wireframe render items
            ##
            elif item.name() == self.sWireframeItemName or item.name() == self.sShadedTemplateItemName or item.name() == self.sSelectedWireframeItemName or (item.primitive() != omr.MGeometry.kTriangles and item.name() == self.sShadedProxyItemName):
                self.updateIndexingForWireframeItems(wireIndexBuffer, item, data, totalVerts)

            ## Handle indexing for affected edge render items
            ## For each face we check the edges. If the edges are in the active vertex
            ## list we add indexing for the 2 vertices on the edge to the index buffer.
            ##
            elif item.name() == self.sAffectedEdgeItemName:
                self.updateIndexingForEdges(item, data, totalVerts, True) ## Filter edges using active edges or actives vertices set
            elif item.name() == self.sEdgeSelectionItemName:
                self.updateIndexingForEdges(item, data, totalVerts, False) ## No filter : all edges

            ## Handle indexing for affected edge render items
            ## For each triangle we check the vertices. If any of the vertices are in the active vertex
            ## list we add indexing for the triangle to the index buffer.
            ##
            elif item.name() == self.sAffectedFaceItemName:
                self.updateIndexingForFaces(item, data, numTriangles, True) ## Filter faces using active faces or actives vertices set
            elif item.name() == self.sFaceSelectionItemName:
                self.updateIndexingForFaces(item, data, numTriangles, False) ## No filter : all faces

            ## Create indexing for filled (shaded) render items
            ##
            elif item.primitive() == omr.MGeometry.kTriangles:
                self.updateIndexingForShadedTriangles(item, data, numTriangles)

        if debugPopulateGeometry:
            print("> End populate geometry")

    def cleanUp(self):
        self.fMeshGeom = None
        self.fActiveVertices.clear()
        self.fActiveVerticesSet = set()
        self.fActiveEdgesSet = set()
        self.fActiveFacesSet = set()

    def updateSelectionGranularity(self, path, selectionContext):
        ## This is method is called during the pre-filtering phase of the viewport 2.0 selection
        ## and is used to setup the selection context of the given DAG object.

        ## We want the whole shape to be selectable, so we set the selection level to kObject so that the shape
        ## will be processed by the selection.

        ## In case we are currently in component selection mode (vertex, edge or face),
        ## since we have created render items that can be use in the selection phase (kSelectionOnly draw mode)
        ## and we also registered component converters to handle this render items,
        ## we can set the selection level to kComponent so that the shape will also be processed by the selection.

        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        if displayStatus == omr.MGeometryUtilities.kHilite:
    
            globalComponentMask = om.MGlobal.objectSelectionMask()
            if om.MGlobal.selectionMode() == om.MGlobal.kSelectComponentMode:
                globalComponentMask = om.MGlobal.componentSelectionMask()

            supportedComponentMask = om.MSelectionMask( om.MSelectionMask.kSelectMeshVerts )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectMeshEdges )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectMeshFaces )
            supportedComponentMask.addMask( om.MSelectionMask.kSelectPointsForGravity )
            
            if globalComponentMask.intersects(supportedComponentMask):
                selectionContext.selectionLevel = omr.MSelectionContext.kComponent
        elif omr.MPxGeometryOverride.pointSnappingActive():
            selectionContext.selectionLevel = omr.MSelectionContext.kComponent

    def printShader(self, shader):
        ## Some example code to print out shader parameters
        if not shader:
            return

        params = shader.parameterList()
        print("DEBUGGING SHADER, BEGIN PARAM LIST OF LENGTH " + str(len(params)))

        for param in params:
            paramType = shader.parameterType(param)
            isArray = shader.isArrayParameter(param)

            typeAsStr = "Unknown"
            if paramType == omr.MShaderInstance.kInvalid:
                typeAsStr = "Invalid"
            elif paramType == omr.MShaderInstance.kBoolean:
                typeAsStr = "Boolean"
            elif paramType == omr.MShaderInstance.kInteger:
                typeAsStr = "Integer"
            elif paramType == omr.MShaderInstance.kFloat:
                typeAsStr = "Float"
            elif paramType == omr.MShaderInstance.kFloat2:
                typeAsStr = "Float2"
            elif paramType == omr.MShaderInstance.kFloat3:
                typeAsStr = "Float3"
            elif paramType == omr.MShaderInstance.kFloat4:
                typeAsStr = "Float4"
            elif paramType == omr.MShaderInstance.kFloat4x4Row:
                typeAsStr = "Float4x4Row"
            elif paramType == omr.MShaderInstance.kFloat4x4Col:
                typeAsStr = "Float4x4Col"
            elif paramType == omr.MShaderInstance.kTexture1:
                typeAsStr = "1D Texture"
            elif paramType == omr.MShaderInstance.kTexture2:
                typeAsStr = "2D Texture"
            elif paramType == omr.MShaderInstance.kTexture3:
                typeAsStr = "3D Texture"
            elif paramType == omr.MShaderInstance.kTextureCube:
                typeAsStr = "Cube Texture"
            elif paramType == omr.MShaderInstance.kSampler:
                typeAsStr = "Sampler"

            print("ParamName='" + param + "', ParamType='" + typeAsStr + "', IsArrayParameter:'" + str(isArray) + "'")

        print("END PARAM LIST")

    def setSolidColor(self, shaderInstance, defaultColor, customColor=None):
        ## Set the solid color for solid color shaders
        if shaderInstance:
            color = defaultColor
            if self.fUseCustomColors and customColor:
                color = customColor
            try:
                shaderInstance.setParameter("solidColor", color)
            except:
                pass

    def setSolidPointSize(self, shaderInstance, size):
        ## Set the point size for solid color shaders
        if shaderInstance:
            try:
                shaderInstance.setParameter("pointSize", [size, size])
            except:
                pass

    def setLineWidth(self, shaderInstance, width):
        ## Set the line width for solid color shaders
        if shaderInstance:
            try:
                shaderInstance.setParameter("lineWidth", [width, width])
            except:
                pass

    def enableActiveComponentDisplay(self, path):
        ## Test to see if active components should be enabled.
        ## Based on active vertices + non-template state

        enable = True

        ## If there are components then we need to check
        ## either the display status of the object, or
        ## in the case of a templated object make sure
        ## to hide components to be consistent with how
        ## internal objects behave
        ##
        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        if displayStatus == omr.MGeometryUtilities.kHilite or displayStatus == omr.MGeometryUtilities.kActiveComponent:
            enable = False
        
        else:
            ## Do an explicit path test for templated
            ## since display status does not indicate this.
            if path.isTemplated():
                enable = False

        return enable

    ## Render item handling methods
    def updateDormantAndTemplateWireframeItems(self, path, list, shaderMgr):
        ## Update render items for dormant and template wireframe drawing.
        ## 
        ## 1) If the object is dormant and not templated then we require
        ## a render item to display when wireframe drawing is required (display modes
        ## is wire or wire-on-shaded)
        ## 
        ## 2a) If the object is templated then we use the same render item as in 1)
        ## when in wireframe drawing is required.
        ## 2b) However we also require a render item to display when in shaded mode.
    
        ## Stock colors
        dormantColor = [ 0.0, 0.0, 1.0, 1.0 ]
        templateColor = [ 0.45, 0.45, 0.45, 1.0 ]
        activeTemplateColor = [ 1.0, 0.5, 0.5, 1.0 ]

        ## Some local options to show debug interface
        ##
        debugShader = False

        ## Get render item used for draw in wireframe mode
        ## (Mode to draw in is omr.MGeometry.kWireframe)
        ##
        wireframeItem = None
        index = list.indexOf(self.sWireframeItemName)
        if index < 0:
            wireframeItem = omr.MRenderItem.create( self.sWireframeItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            wireframeItem.setDrawMode(omr.MGeometry.kWireframe)

            ## Set dormant wireframe with appropriate priority to not clash with
            ## any active wireframe which may overlap in depth.
            wireframeItem.setDepthPriority( omr.MRenderItem.sDormantWireDepthPriority )

            list.append(wireframeItem)

            preCb = None
            postCb = None
            if debugShader:
                preCb = apiMeshPreDrawCallback
                postCb = apiMeshPostDrawCallback

            shader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader, preCb, postCb)
            if shader:
                ## assign shader
                wireframeItem.setShader(shader)

                ## sample debug code
                if debugShader:
                    self.printShader( shader )

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            wireframeItem = list[index]

        ## Get render item for handling mode shaded template drawing
        ##
        shadedTemplateItem = None
        index = list.indexOf(self.sShadedTemplateItemName)
        if index < 0:
            shadedTemplateItem = omr.MRenderItem.create( self.sShadedTemplateItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            shadedTemplateItem.setDrawMode(omr.MGeometry.kAll)

            ## Set shaded item as being dormant wire since it should still be raised
            ## above any shaded items, but not as high as active items.
            shadedTemplateItem.setDepthPriority( omr.MRenderItem.sDormantWireDepthPriority )

            list.append(shadedTemplateItem)

            shader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader)
            if shader:
                ## assign shader
                shadedTemplateItem.setShader(shader)

                ## sample debug code
                if debugShader:
                    self.printShader( shader )

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            shadedTemplateItem = list[index]

        ## Sample code to disable cast, receives shadows, and post effects.
        shadedTemplateItem.setCastsShadows( not self.fExternalItemsNonTri_NoShadowCast )
        shadedTemplateItem.setReceivesShadows( not self.fExternalItemsNonTri_NoShadowReceive )
        shadedTemplateItem.setExcludedFromPostEffects( self.fExternalItemsNonTri_NoPostEffects )

        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        wireColor = omr.MGeometryUtilities.wireframeColor(path)

        ## Enable / disable wireframe item and update the shader parameters
        ##
        if wireframeItem:
            shader = wireframeItem.getShader()

            if displayStatus == omr.MGeometryUtilities.kTemplate:
                self.setSolidColor( shader, wireColor, templateColor)
                wireframeItem.enable(True)

            elif displayStatus == omr.MGeometryUtilities.kActiveTemplate:
                self.setSolidColor( shader, wireColor, activeTemplateColor)
                wireframeItem.enable(True)

            elif displayStatus == omr.MGeometryUtilities.kDormant:
                self.setSolidColor( shader, wireColor, dormantColor)
                wireframeItem.enable(True)

            elif displayStatus == omr.MGeometryUtilities.kActiveAffected:
                theColor = [ 0.5, 0.0, 1.0, 1.0 ]
                self.setSolidColor( shader, wireColor, theColor)
                wireframeItem.enable(True)

            else:
                wireframeItem.enable(False)

        ## Enable / disable shaded/template item and update the shader parameters
        ##
        if shadedTemplateItem:
            isTemplate = path.isTemplated()
            shader = shadedTemplateItem.getShader()

            if displayStatus == omr.MGeometryUtilities.kTemplate:
                self.setSolidColor( shader, wireColor, templateColor)
                shadedTemplateItem.enable(isTemplate)

            elif displayStatus == omr.MGeometryUtilities.kActiveTemplate:
                self.setSolidColor( shader, wireColor, activeTemplateColor)
                shadedTemplateItem.enable(isTemplate)

            elif displayStatus == omr.MGeometryUtilities.kDormant:
                self.setSolidColor( shader, wireColor, dormantColor)
                shadedTemplateItem.enable(isTemplate)

            else:
                shadedTemplateItem.enable(False)

    def updateActiveWireframeItem(self, path, list, shaderMgr):
        ## Create a render item for active wireframe if it does not exist. Updating
        ## shading parameters as necessary.

        selectItem = None
        index = list.indexOf(self.sSelectedWireframeItemName)
        if index < 0:
            selectItem = omr.MRenderItem.create(self.sSelectedWireframeItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            selectItem.setDrawMode(omr.MGeometry.kAll)
            ## This is the same as setting the argument raiseAboveShaded = True,/
            ## since it sets the priority value to be the same. This line is just
            ## an example of another way to do the same thing after creation of
            ## the render item.
            selectItem.setDepthPriority( omr.MRenderItem.sActiveWireDepthPriority )
            list.append(selectItem)

            ## For active wireframe we will use a shader which allows us to draw thick lines
            ##
            drawThick = False
            shaderId = omr.MShaderManager.k3dSolidShader
            if drawThick:
                shaderId = omr.MShaderManager.k3dThickLineShader

            shader = shaderMgr.getStockShader(shaderId)
            if shader:
                ## assign shader
                selectItem.setShader(shader)
                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            selectItem = list[index]

        shader = None
        if selectItem:
            shader = selectItem.getShader()

        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        wireColor = omr.MGeometryUtilities.wireframeColor(path)

        if displayStatus == omr.MGeometryUtilities.kLead:
            theColor = [ 0.0, 0.8, 0.0, 1.0 ]
            self.setSolidColor( shader, wireColor, theColor)
            selectItem.enable(True)

        elif displayStatus == omr.MGeometryUtilities.kActive:
            theColor = [ 1.0, 1.0, 1.0, 1.0 ]
            self.setSolidColor( shader, wireColor, theColor)
            selectItem.enable(True)

        elif displayStatus == omr.MGeometryUtilities.kHilite or displayStatus == omr.MGeometryUtilities.kActiveComponent:
            theColor = [ 0.0, 0.5, 0.7, 1.0 ]
            self.setSolidColor( shader, wireColor, theColor)
            selectItem.enable(True)

        else:
            selectItem.enable(False)

        ## Add custom user data to selection item
        myCustomData = selectItem.getCustomData()
        if not myCustomData:
            ## create the custom data
            myCustomData = apiMeshUserData()
            myCustomData.fMessage = "I'm custom data!"
            selectItem.setCustomData(myCustomData)
        else:
            ## modify the custom data
            myCustomData.fNumModifications += 1

    def updateWireframeModeFaceCenterItem(self, path, list, shaderMgr):
        ## Add render item for face centers in wireframe mode, always show face centers
        ## in wireframe mode except it is drawn as template.

        wireframeModeFaceCenterItem = None
        index = list.indexOf(self.sWireframeModeFaceCenterItemName)
        if index < 0:
            wireframeModeFaceCenterItem = omr.MRenderItem.create(self.sWireframeModeFaceCenterItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            wireframeModeFaceCenterItem.setDrawMode(omr.MGeometry.kWireframe)
            wireframeModeFaceCenterItem.setDepthPriority( omr.MRenderItem.sActiveWireDepthPriority )

            list.append(wireframeModeFaceCenterItem)

            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dFatPointShader )
            if shader:
                ## Set the point size parameter. Make it slightly larger for face centers
                pointSize = 5.0
                self.setSolidPointSize( shader, pointSize )

                wireframeModeFaceCenterItem.setShader(shader, self.sFaceCenterStreamName )

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
            else:
                wireframeModeFaceCenterItem = list[index]

        if wireframeModeFaceCenterItem:
            shader = wireframeModeFaceCenterItem.getShader()
            if shader:
                ## Set face center color in wireframe mode
                theColor = [ 0.0, 0.0, 1.0, 1.0 ]
                self.setSolidColor( shader, theColor )

            ## disable the face center item when template
            isTemplate = path.isTemplated()
            wireframeModeFaceCenterItem.enable( not isTemplate )

    def updateShadedModeFaceCenterItem(self, path, list, shaderMgr):
        ##Add render item for face centers in shaded mode. If the geometry is not selected,
        ## face centers are not drawn.

        shadedModeFaceCenterItem = None
        index = list.indexOf(self.sShadedModeFaceCenterItemName)
        if index < 0:
            shadedModeFaceCenterItem = omr.MRenderItem.create( self.sShadedModeFaceCenterItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            shadedModeFaceCenterItem.setDrawMode(omr.MGeometry.kShaded | omr.MGeometry.kTextured)

            shadedModeFaceCenterItem.setDepthPriority(omr.MRenderItem.sActivePointDepthPriority)

            list.append(shadedModeFaceCenterItem)

            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dFatPointShader )
            if shader:
                ## Set the point size parameter. Make it slightly larger for face centers
                pointSize = 5.0
                self.setSolidPointSize( shader, pointSize )

                shadedModeFaceCenterItem.setShader(shader, self.sFaceCenterStreamName )

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            shadedModeFaceCenterItem = list[index]

        if shadedModeFaceCenterItem:
            shadedModeFaceCenterItem.setExcludedFromPostEffects(True)

            shader = shadedModeFaceCenterItem.getShader()
            wireColor = omr.MGeometryUtilities.wireframeColor(path)

            if shader:
                ## Set face center color in shaded mode
                self.setSolidColor( shader, wireColor )

            displayStatus = omr.MGeometryUtilities.displayStatus(path)
            if displayStatus == omr.MGeometryUtilities.kActive or displayStatus == omr.MGeometryUtilities.kLead or displayStatus == omr.MGeometryUtilities.kActiveComponent or displayStatus == omr.MGeometryUtilities.kLive or displayStatus == omr.MGeometryUtilities.kHilite:
                shadedModeFaceCenterItem.enable(True)

            else:
                shadedModeFaceCenterItem.enable(False)

    def updateDormantVerticesItem(self, path, list, shaderMgr):
        ## Create a render item for dormant vertices if it does not exist. Updating
        ## shading parameters as necessary.

        vertexItem = None
        index = list.indexOf(self.sVertexItemName)
        if index < 0:
            vertexItem = omr.MRenderItem.create(self.sVertexItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)

            ## Set draw mode to kAll : the item will be visible in the viewport and also during viewport 2.0 selection
            vertexItem.setDrawMode(omr.MGeometry.kAll)

            ## Set the selection mask to kSelectMeshVerts : we want the render item to be used for Vertex Components selection
            mask = om.MSelectionMask(om.MSelectionMask.kSelectMeshVerts)
            mask.addMask(om.MSelectionMask.kSelectPointsForGravity)
            vertexItem.setSelectionMask( mask )

            ## Set depth priority higher than wireframe and shaded render items,
            ## but lower than active points.
            ## Raising higher than wireframe will make them not seem embedded into the surface
            vertexItem.setDepthPriority( omr.MRenderItem.sDormantPointDepthPriority )
            list.append(vertexItem)

            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dFatPointShader )
            if shader:
                ## Set the point size parameter
                pointSize = 3.0
                self.setSolidPointSize( shader, pointSize )

                ## assign shader
                vertexItem.setShader(shader)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            vertexItem = list[index]

        if vertexItem:
            shader = vertexItem.getShader()
            ## set color
            theColor = [ 0.0, 0.0, 1.0, 1.0 ]
            self.setSolidColor( shader, theColor )

            displayStatus = omr.MGeometryUtilities.displayStatus(path)

            ## Generally if the display status is hilite then we
            ## draw components.
            if displayStatus == omr.MGeometryUtilities.kHilite or omr.MPxGeometryOverride.pointSnappingActive():
                ## In case the object is templated
                ## we will hide the components to be consistent
                ## with how internal objects behave.
                if path.isTemplated():
                    vertexItem.enable(False)
                else:
                    vertexItem.enable(True)
            else:
                vertexItem.enable(False)

            mySelectionData = vertexItem.getCustomData()
            if not isinstance(mySelectionData, apiMeshHWSelectionUserData):
                ## create the custom data
                mySelectionData = apiMeshHWSelectionUserData()
                vertexItem.setCustomData(mySelectionData)
            ## update the custom data
            mySelectionData.fMeshGeom = self.fMeshGeom

    def updateActiveVerticesItem(self, path, list, shaderMgr):
        ## Create a render item for active vertices if it does not exist. Updating
        ## shading parameters as necessary.

        activeItem = None
        index = list.indexOf(self.sActiveVertexItemName)
        if index < 0:
            activeItem = omr.MRenderItem.create(self.sActiveVertexItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            activeItem.setDrawMode(omr.MGeometry.kAll)
            ## Set depth priority to be active point. This should offset it
            ## to be visible above items with "dormant point" priority.
            activeItem.setDepthPriority( omr.MRenderItem.sActivePointDepthPriority )
            list.append(activeItem)

            shaderId = omr.MShaderManager.k3dFatPointShader
            if self.fDrawActiveVerticesWithRamp:
                shaderId = omr.MShaderManager.k3dColorLookupFatPointShader

            shader = shaderMgr.getStockShader( shaderId )
            if shader:
                ## Set the point size parameter. Make it slightly larger for active vertices
                pointSize = 5.0
                self.setSolidPointSize( shader, pointSize )

                ## 1D Ramp color lookup option
                ##
                if self.fDrawActiveVerticesWithRamp:
                    textureMgr = omr.MRenderer.getTextureManager()

                    ## Assign dummy ramp lookup
                    if not self.fColorRemapTexture:
                        ## Sample 3 colour ramp
                        colorArray = [  1.0, 0.0, 0.0, 1.0,
                                        0.0, 1.0, 0.0, 1.0,
                                        0.0, 0.0, 1.0, 1.0 ]

                        arrayLen = 3
                        textureDesc = omr.MTextureDescription()
                        textureDesc.setToDefault2DTexture()
                        textureDesc.fWidth = arrayLen
                        textureDesc.fHeight = 1
                        textureDesc.fDepth = 1
                        textureDesc.fBytesPerSlice = textureDesc.fBytesPerRow = 24*arrayLen
                        textureDesc.fMipmaps = 1
                        textureDesc.fArraySlices = 1
                        textureDesc.fTextureType = omr.MRenderer.kImage1D
                        textureDesc.fFormat = omr.MRenderer.kR32G32B32A32_FLOAT
                        self.fColorRemapTexture = textureMgr.acquireTexture("", textureDesc, colorArray, False)

                    if not self.fLinearSampler:
                        samplerDesc = omr.MSamplerStateDesc()
                        samplerDesc.addressU = omr.MSamplerState.kTexClamp
                        samplerDesc.addressV = omr.MSamplerState.kTexClamp
                        samplerDesc.addressW = omr.MSamplerState.kTexClamp
                        samplerDesc.filter = omr.MSamplerState.kMinMagMipLinear
                        fLinearSampler = omr.MStateManager.acquireSamplerState(samplerDesc)

                    if self.fColorRemapTexture and self.fLinearSampler:
                        ## Set up the ramp lookup
                        shader.setParameter("map", self.fColorRemapTexture)
                        shader.setParameter("samp", self.fLinearSampler)

                        ## No remapping. The initial data created in the xrange 0...1
                        ##
                        rampValueRange = om.MFloatVector(0.0, 1.0)
                        shader.setParameter("UVRange", rampValueRange)

                ## Assign shader. Use a named stream if we want to supply a different
                ## set of "shared" vertices for drawing active vertices
                if self.fDrawSharedActiveVertices:
                    activeItem.setShader(shader, self.sActiveVertexStreamName)
                else:
                    activeItem.setShader(shader, None)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)

        else:
            activeItem = list[index]

        if activeItem:
            shader = activeItem.getShader()
            if shader:
                ## Set active color
                theColor = [ 1.0, 1.0, 0.0, 1.0 ]
                self.setSolidColor( shader, theColor )

            enable = (bool(self.fActiveVerticesSet) and self.enableActiveComponentDisplay(path))
            activeItem.enable( enable )

    def updateVertexNumericItems(self, path, list, shaderMgr):
        ## Create render items for numeric display, and update shaders as necessary



        ## Vertex id item
        ##
        vertexItem = None
        index = list.indexOf(self.sVertexIdItemName)
        if index < 0:
            vertexItem = omr.MRenderItem.create( self.sVertexIdItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            vertexItem.setDrawMode(omr.MGeometry.kAll)
            vertexItem.setDepthPriority( omr.MRenderItem.sDormantPointDepthPriority )
            list.append(vertexItem)

            ## Use single integer numeric shader
            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dIntegerNumericShader )
            if shader:
                ## Label the fields so that they can be found later on.
                vertexItem.setShader(shader, self.sVertexIdItemName)
                shaderMgr.releaseShader(shader)
        else:
            vertexItem = list[index]

        if vertexItem:
            shader = vertexItem.getShader()
            if shader:
                ## set color
                theColor = [ 1.0, 1.0, 0.0, 1.0 ]
                self.setSolidColor( shader, theColor )

            vertexItem.enable(self.fEnableNumericDisplay)

        ## Vertex position numeric render item
        ##
        vertexItem = None
        index = list.indexOf(self.sVertexPositionItemName)
        if index < 0:
            vertexItem = omr.MRenderItem.create( self.sVertexPositionItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kPoints)
            vertexItem.setDrawMode(omr.MGeometry.kAll)
            vertexItem.setDepthPriority( omr.MRenderItem.sDormantPointDepthPriority )
            list.append(vertexItem)

            ## Use triple float numeric shader
            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dFloat3NumericShader )
            if shader:
                ##vertexItem.setShader(shader)
                vertexItem.setShader(shader, self.sVertexPositionItemName)
                shaderMgr.releaseShader(shader)
        else:
            vertexItem = list[index]

        if vertexItem:
            shader = vertexItem.getShader()
            if shader:
                ## set color
                theColor = [ 0.0, 1.0, 1.0, 1.0 ]
                self.setSolidColor( shader, theColor)

            vertexItem.enable(self.fEnableNumericDisplay)

    def updateAffectedComponentItems(self, path, list, shaderMgr):
        ## Example of adding in items to hilite edges and faces. In this
        ## case these are edges and faces which are connected to vertices
        ## and we thus call them "affected" components.

        ## Create / update "affected/active" edges component render item.
        ##
        componentItem = None
        index = list.indexOf(self.sAffectedEdgeItemName)
        if index < 0:
            componentItem = omr.MRenderItem.create( self.sAffectedEdgeItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)
            componentItem.setDrawMode(omr.MGeometry.kAll)

            ## Set depth priority to be active line so that it is above wireframe
            ## but below dormant and active points.
            componentItem.setDepthPriority( omr.MRenderItem.sActiveLineDepthPriority )
            list.append(componentItem)

            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dThickLineShader )
            if shader:
                ## Set lines a bit thicker to stand out
                lineSize = 1.0
                self.setLineWidth( shader, lineSize )

                ## Assign shader.
                componentItem.setShader(shader, None)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            componentItem = list[index]

        if componentItem:
            shader = componentItem.getShader()
            if shader:
                ## Set affected color
                theColor = [ 1.0, 1.0, 1.0, 1.0 ]
                self.setSolidColor( shader, theColor )

            enable = ((bool(self.fActiveVerticesSet) or bool(self.fActiveEdgesSet)) and self.enableActiveComponentDisplay(path))
            componentItem.enable( enable )

        ################################################################################

        ## Create / update "affected/active" faces component render item
        ##
        componentItem = None
        index = list.indexOf(self.sAffectedFaceItemName)
        if index < 0:
            componentItem = omr.MRenderItem.create( self.sAffectedFaceItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kTriangles)
            componentItem.setDrawMode(omr.MGeometry.kAll)
            ## Set depth priority to be dormant wire so that edge and vertices
            ## show on top.
            componentItem.setDepthPriority( omr.MRenderItem.sDormantWireDepthPriority )
            
            ## Allow render item copies to be created for isolate selected component
            componentItem.setAllowIsolateSelectCopy(True)
            
            list.append(componentItem)

            shader = shaderMgr.getStockShader( omr.MShaderManager.k3dStippleShader )
            if shader:
                ## Assign shader.
                componentItem.setShader(shader, None)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            componentItem = list[index]

        if componentItem:
            shader = componentItem.getShader()
            if shader:
                ## Set affected color
                theColor = [ 1.0, 1.0, 1.0, 1.0 ]
                self.setSolidColor( shader, theColor )

            enable = ((bool(self.fActiveVerticesSet) or bool(self.fActiveFacesSet)) and self.enableActiveComponentDisplay(path))
            componentItem.enable( enable )

    def updateSelectionComponentItems(self, path, list, shaderMgr):
        ## Example of adding in items for edges and faces selection.

        ## For the vertex selection, we already have a render item that display all the vertices (sVertexItemName)
        ## we could use it for the selection as well.
    
        ## But we have none that display the complete edges or faces,
        ## sAffectedEdgeItemName and sAffectedFaceItemName only display a subset of the edges and faces
        ## that are active or affected (one of their vertices is selected).

        ## In order to be able to perform the selection of this components we'll create new render items
        ## that will only be used for the selection (they will not be visible in the viewport)

        ## Create / update selection edges component render item.
        ##
        selectionItem = None
        index = list.indexOf(self.sEdgeSelectionItemName)
        if index < 0:
            selectionItem = omr.MRenderItem.create( self.sEdgeSelectionItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kLines)

            ## Set draw mode to kSelectionOnly : the item will not be visible in the viewport, but during viewport 2.0 selection
            selectionItem.setDrawMode(omr.MGeometry.kSelectionOnly)

            ## Set the selection mask to kSelectMeshEdges : we want the render item to be used for Edge Components selection
            selectionItem.setSelectionMask( om.MSelectionMask.kSelectMeshEdges )

            ## Set depth priority to be selection so that it is above everything
            selectionItem.setDepthPriority( omr.MRenderItem.sSelectionDepthPriority )
            list.append(selectionItem)

            shader = shaderMgr.getStockShader(omr.MShaderManager.k3dThickLineShader)
            if shader:
                ## Assign shader.
                selectionItem.setShader(shader, None)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            selectionItem = list[index]

        if selectionItem:
            selectionItem.enable(True)

            mySelectionData = selectionItem.getCustomData()
            if not isinstance(mySelectionData, apiMeshHWSelectionUserData):
                ## create the custom data
                mySelectionData = apiMeshHWSelectionUserData()
                selectionItem.setCustomData(mySelectionData)
            ## update the custom data
            mySelectionData.fMeshGeom = self.fMeshGeom

        ## Create / update selection faces component render item.
        ##
        index = list.indexOf(self.sFaceSelectionItemName)
        if index < 0:
            selectionItem = omr.MRenderItem.create( self.sFaceSelectionItemName, omr.MRenderItem.DecorationItem, omr.MGeometry.kTriangles)

            ## Set draw mode to kSelectionOnly : the item will not be visible in the viewport, but during viewport 2.0 selection
            selectionItem.setDrawMode(omr.MGeometry.kSelectionOnly)

            ## Set the selection mask to kSelectMeshFaces : we want the render item to be used for Face Components selection
            selectionItem.setSelectionMask( om.MSelectionMask.kSelectMeshFaces )

            ## Set depth priority to be selection so that it is above everything
            selectionItem.setDepthPriority( omr.MRenderItem.sSelectionDepthPriority )

            ## Allow render item copies to be created for isolate selected component
            selectionItem.setAllowIsolateSelectCopy(True)

            list.append(selectionItem)

            shader = shaderMgr.getStockShader(omr.MShaderManager.k3dSolidShader)
            if shader:
                ## Assign shader.
                selectionItem.setShader(shader, None)

                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            selectionItem = list[index]

        if selectionItem:
            selectionItem.enable(True)

            mySelectionData = selectionItem.getCustomData()
            if not isinstance(mySelectionData, apiMeshHWSelectionUserData):
                ## create the custom data
                mySelectionData = apiMeshHWSelectionUserData()
                selectionItem.setCustomData(mySelectionData)
            ## update the custom data
            mySelectionData.fMeshGeom = self.fMeshGeom

    def updateProxyShadedItem(self, path, list, shaderMgr):
        ## In the event there are no shaded items we create a proxy
        ## render item so we can still see where the object is.

        ## Stock colors
        dormantColor = [ 0.0, 0.0, 1.0, 1.0 ]
        templateColor = [ 0.45, 0.45, 0.45, 1.0 ]
        activeTemplateColor = [ 1.0, 0.5, 0.5, 1.0 ]

        ## Note that we still want to raise it above shaded even though
        ## we don't have a shaded render item for this override.
        ## This will handle in case where there is another shaded object
        ## which overlaps this object in depth
        ##
        raiseAboveShaded = True
        shadedDrawMode = omr.MGeometry.kShaded | omr.MGeometry.kTextured
        ## Mark proxy item as wireframe if not using a material shader
        ##
        useFragmentShader = self.fProxyShader < 0
        if not useFragmentShader:
            shadedDrawMode |= omr.MGeometry.kWireframe

        ## Fragment + stipple shaders required triangles. All others
        ## in the possible list requires lines
        ##
        itemType = omr.MRenderItem.NonMaterialSceneItem
        primitive = omr.MGeometry.kLines
        filledProxy = useFragmentShader or self.fProxyShader == omr.MShaderManager.k3dStippleShader
        if filledProxy:
            itemType = omr.MRenderItem.MaterialSceneItem
            primitive = omr.MGeometry.kTriangles

        depthPriority = omr.MRenderItem.sDormantWireDepthPriority
        if raiseAboveShaded:
            depthPriority = omr.MRenderItem.sActiveWireDepthPriority

        proxyItem = None
        index = list.indexOf(self.sShadedProxyItemName)
        if index < 0:
            proxyItem = omr.MRenderItem.create( self.sShadedProxyItemName, itemType, primitive)
            proxyItem.setDrawMode(shadedDrawMode)
            proxyItem.setDepthPriority( depthPriority )

            proxyItem.setCastsShadows( not self.fExternalItems_NoShadowCast and self.fCastsShadows )
            proxyItem.setReceivesShadows( not self.fExternalItems_NoShadowReceive and self.fReceivesShadows )
            proxyItem.setExcludedFromPostEffects( self.fExternalItems_NoPostEffects )

            list.append(proxyItem)

            ## We'll draw the proxy with a proxy shader as a visual cue
            ##
            shader = None
            if useFragmentShader:
                shader = shaderMgr.getFragmentShader("mayaLambertSurface", "outSurfaceFinal", True)
                sBlue = [ 0.4, 0.4, 1.0 ]
                shader.setParameter("color", sBlue)
                shader.setIsTransparent(False)
            else:
                shader = shaderMgr.getStockShader( self.fProxyShader )

            if shader:
                if not filledProxy:
                    self.setLineWidth(shader, 10.0)

                ## assign shader
                proxyItem.setShader(shader)
                ## once assigned, no need to hold on to shader instance
                shaderMgr.releaseShader(shader)
        else:
            proxyItem = list[index]

        ## As this is a shaded item it is up to the plug-in to determine
        ## on each update how to handle shadowing and effects.
        ## Especially note that shadowing changes on the DAG object will trigger
        ## a call to updateRenderItems()
        ##
        proxyItem.setCastsShadows( not self.fExternalItems_NoShadowCast and self.fCastsShadows )
        proxyItem.setReceivesShadows( not self.fExternalItems_NoShadowReceive and self.fReceivesShadows )
        proxyItem.setExcludedFromPostEffects( self.fExternalItems_NoPostEffects )

        ## Check for any shaded render items. A lack of one indicates
        ## there is no shader assigned to the object.
        ##
        haveShadedItems = False
        for item in list:
            if not item:
                continue
            drawMode = item.drawMode()
            if drawMode == omr.MGeometry.kShaded or drawMode == omr.MGeometry.kTextured:
                if item.name() != self.sShadedTemplateItemName:
                    haveShadedItems = True
                    break

        displayStatus = omr.MGeometryUtilities.displayStatus(path)
        wireColor = omr.MGeometryUtilities.wireframeColor(path)

        ## Note that we do not toggle the item on and off just based on
        ## display state. If this was so then call to MRenderer::setLightsAndShadowsDirty()
        ## would be required as shadow map update does not monitor display state.
        ##
        if proxyItem:
            shader = proxyItem.getShader()

            if displayStatus == omr.MGeometryUtilities.kTemplate:
                self.setSolidColor( shader, wireColor, templateColor )

            elif displayStatus == omr.MGeometryUtilities.kActiveTemplate:
                self.setSolidColor( shader, wireColor, activeTemplateColor )

            elif displayStatus == omr.MGeometryUtilities.kDormant:
                self.setSolidColor( shader, wireColor, dormantColor )

            ## If we are missing shaded render items then enable
            ## the proxy. Otherwise disable it.
            ##
            if filledProxy:
                ## If templated then hide filled proxy
                if path.isTemplated():
                    proxyItem.enable(False)
                else:
                    proxyItem.enable(not haveShadedItems)
            else:
                proxyItem.enable(not haveShadedItems)

    ## Data stream (geometry requirements) handling
    def updateGeometryRequirements(self, requirements, data, activeVertexCount, totalVerts, debugPopulateGeometry):
        ## Examine the geometry requirements and create / update the
        ## appropriate data streams. As render items specify both named and
        ## unnamed data streams, both need to be handled here.

        ## Vertex data
        positionBuffer = None
        positionDataAddress = None
        positionData = None

        vertexNumericIdBuffer = None
        vertexNumericIdDataAddress = None
        vertexNumericIdData = None

        vertexNumericIdPositionBuffer = None
        vertexNumericIdPositionDataAddress = None
        vertexNumericIdPositionData = None

        vertexNumericLocationBuffer = None
        vertexNumericLocationDataAddress = None
        vertexNumericLocationData = None

        vertexNumericLocationPositionBuffer = None
        vertexNumericLocationPositionDataAddress = None
        vertexNumericLocationPositionData = None

        activeVertexPositionBuffer = None
        activeVertexPositionDataAddress = None
        activeVertexPositionData = None

        activeVertexUVBuffer = None
        activeVertexUVDataAddress = None
        activeVertexUVData = None

        faceCenterPositionBuffer = None
        faceCenterPositionDataAddress = None
        faceCenterPositionData = None

        normalBuffer = None
        normalDataAddress = None
        normalData = None

        cpvBuffer = None
        cpvDataAddress = None
        cpvData = None

        uvBuffer = None
        uvDataAddress = None
        uvData = None

        numUVs = self.fMeshGeom.uvcoords.uvcount()

        descList = requirements.vertexRequirements()
        satisfiedRequirements = [False,] * len(descList)
        for i in range(len(descList)):
            desc = descList[i]
            ## Fill in vertex data for drawing active vertex components (if drawSharedActiveVertices=True)
            ##
            if self.fDrawSharedActiveVertices and (desc.name == self.sActiveVertexStreamName):
                if desc.semantic == omr.MGeometry.kPosition:
                    if not activeVertexPositionBuffer:
                        activeVertexPositionBuffer = data.createVertexBuffer(desc)
                        if activeVertexPositionBuffer:
                            satisfiedRequirements[i] = True
                            if debugPopulateGeometry:
                                print(">>> Fill in data for active vertex requirement '" + desc.name + "'. Semantic = kPosition")
                            activeVertexPositionDataAddress = activeVertexPositionBuffer.acquire(activeVertexCount, True) ## writeOnly - we don't need the current buffer values
                            if activeVertexPositionDataAddress:
                                activeVertexPositionData = ((ctypes.c_float * 3)*activeVertexCount).from_address(activeVertexPositionDataAddress)

                elif desc.semantic == omr.MGeometry.kTexture:
                    if not activeVertexUVBuffer:
                        activeVertexUVBuffer = data.createVertexBuffer(desc)
                        if activeVertexUVBuffer:
                            satisfiedRequirements[i] = True
                            if debugPopulateGeometry:
                                print(">>> Fill in data for active vertex requirement '" + desc.name + "'. Semantic = kTexture")
                            activeVertexUVDataAddress = activeVertexUVBuffer.acquire(activeVertexCount, True) ## writeOnly - we don't need the current buffer values
                            if activeVertexUVDataAddress:
                                activeVertexUVData = ((ctypes.c_float * 3)*activeVertexCount).from_address(activeVertexUVDataAddress)
                else:
                    ## do nothing for stuff we don't understand
                    pass

            ## Fill in vertex data for drawing face center components (if fDrawFaceCenters=True)
            ##
            elif self.fDrawFaceCenters and desc.name == self.sFaceCenterStreamName:
                if desc.semantic == omr.MGeometry.kPosition:
                    if not faceCenterPositionBuffer:
                        faceCenterPositionBuffer = data.createVertexBuffer(desc)
                        if faceCenterPositionBuffer:
                            satisfiedRequirements[i] = True
                            if debugPopulateGeometry:
                                print(">>> Fill in data for face center vertex requirement '" + desc.name + "'. Semantic = kPosition")
                            faceCenterPositionDataAddress = faceCenterPositionBuffer.acquire(self.fMeshGeom.faceCount, True) ## writeOnly - we don't need the current buffer values
                            if faceCenterPositionDataAddress:
                                faceCenterPositionData = ((ctypes.c_float * 3)*self.fMeshGeom.faceCount).from_address(faceCenterPositionDataAddress)

                else:
                    ## do nothing for stuff we don't understand
                    pass

            ## Fill vertex stream data used for dormant vertex, wireframe and shaded drawing.
            ## Fill also for active vertices if (fDrawSharedActiveVertices=False)
            else:
                if desc.semantic == omr.MGeometry.kPosition:
                    if desc.name == self.sVertexIdItemName:
                        if not vertexNumericIdPositionBuffer:
                            vertexNumericIdPositionBuffer = data.createVertexBuffer(desc)
                            if vertexNumericIdPositionBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kPosition")
                                    print("Acquire 3loat-numeric position buffer")
                                vertexNumericIdPositionDataAddress = vertexNumericIdPositionBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if vertexNumericIdPositionDataAddress:
                                    vertexNumericIdPositionData = ((ctypes.c_float * 3)*totalVerts).from_address(vertexNumericIdPositionDataAddress)

                    elif desc.name == self.sVertexPositionItemName:
                        if not vertexNumericLocationPositionBuffer:
                            vertexNumericLocationPositionBuffer = data.createVertexBuffer(desc)
                            if vertexNumericLocationPositionBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kPosition")
                                    print("Acquire 3loat-numeric position buffer")
                                vertexNumericLocationPositionDataAddress = vertexNumericLocationPositionBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if vertexNumericLocationPositionDataAddress:
                                    vertexNumericLocationPositionData = ((ctypes.c_float * 3)*totalVerts).from_address(vertexNumericLocationPositionDataAddress)

                    else:
                        if not positionBuffer:
                            positionBuffer = data.createVertexBuffer(desc)
                            if positionBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kPosition")
                                    print("Acquire unnamed position buffer")
                                positionDataAddress = positionBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if positionDataAddress:
                                    positionData = ((ctypes.c_float * 3)*totalVerts).from_address(positionDataAddress)

                elif desc.semantic == omr.MGeometry.kNormal:
                    if not normalBuffer:
                        normalBuffer = data.createVertexBuffer(desc)
                        if normalBuffer:
                            satisfiedRequirements[i] = True
                            if debugPopulateGeometry:
                                print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kNormal")
                            normalDataAddress = normalBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                            if normalDataAddress:
                                normalData = ((ctypes.c_float * 3)*totalVerts).from_address(normalDataAddress)

                elif desc.semantic == omr.MGeometry.kTexture:
                    numericValue = "numericvalue"
                    numeric3Value ="numeric3value"

                    ## Fill in single numeric field
                    if desc.semanticName.lower() == numericValue and desc.name == self.sVertexIdItemName:
                        if not vertexNumericIdBuffer:
                            vertexNumericIdBuffer = data.createVertexBuffer(desc)
                            if vertexNumericIdBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kTexture")
                                    print("Acquire 1loat numeric buffer")
                                vertexNumericIdDataAddress = vertexNumericIdBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if vertexNumericIdDataAddress:
                                    vertexNumericIdData = ((ctypes.c_float * 1)*totalVerts).from_address(vertexNumericIdDataAddress)

                    ## Fill in triple numeric field
                    elif desc.semanticName.lower() == numeric3Value and desc.name == self.sVertexPositionItemName:
                        if not vertexNumericLocationBuffer:
                            vertexNumericLocationBuffer = data.createVertexBuffer(desc)
                            if vertexNumericLocationBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kTexture")
                                    print("Acquire 3loat numeric location buffer")
                                vertexNumericLocationDataAddress = vertexNumericLocationBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if vertexNumericLocationDataAddress:
                                    vertexNumericLocationData = ((ctypes.c_float * 3)*totalVerts).from_address(vertexNumericLocationDataAddress)

                    ## Fill in uv values
                    elif desc.name != self.sVertexIdItemName and desc.name != self.sVertexPositionItemName:
                        if not uvBuffer:
                            uvBuffer = data.createVertexBuffer(desc)
                            if uvBuffer:
                                satisfiedRequirements[i] = True
                                if debugPopulateGeometry:
                                    print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kTexture")
                                    print("Acquire a uv buffer")
                                uvDataAddress = uvBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                                if uvDataAddress:
                                    uvData = ((ctypes.c_float * 2)*totalVerts).from_address(uvDataAddress)

                elif desc.semantic == omr.MGeometry.kColor:
                    if not cpvBuffer:
                        cpvBuffer = data.createVertexBuffer(desc)
                        if cpvBuffer:
                            satisfiedRequirements[i] = True
                            if debugPopulateGeometry:
                                print(">>> Fill in data for requirement '" + desc.name + "'. Semantic = kColor")
                            cpvDataAddress = cpvBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                            if cpvDataAddress:
                                cpvData = ((ctypes.c_float * 4)*totalVerts).from_address(cpvDataAddress)

                else:
                    ## do nothing for stuff we don't understand
                    pass

        vid = 0
        pid = 0
        nid = 0
        uvid = 0
        cid = 0
        for i in range(self.fMeshGeom.faceCount):
            ## ignore degenerate faces
            numVerts = self.fMeshGeom.face_counts[i]
            if numVerts > 2:
                for v in range(numVerts):
                    if any((positionData, vertexNumericIdPositionData, vertexNumericLocationPositionData, vertexNumericLocationData)):
                        position = self.fMeshGeom.vertices[self.fMeshGeom.face_connects[vid]]
                        ## Position used as position
                        if positionData:
                            positionData[pid][0] = position[0]
                            positionData[pid][1] = position[1]
                            positionData[pid][2] = position[2]

                        if vertexNumericIdPositionData:
                            vertexNumericIdPositionData[pid][0] = position[0]
                            vertexNumericIdPositionData[pid][1] = position[1]
                            vertexNumericIdPositionData[pid][2] = position[2]

                        if vertexNumericLocationPositionData:
                            vertexNumericLocationPositionData[pid][0] = position[0]
                            vertexNumericLocationPositionData[pid][1] = position[1]
                            vertexNumericLocationPositionData[pid][2] = position[2]

                        if vertexNumericLocationData:
                            vertexNumericLocationData[pid][0] = position[0]
                            vertexNumericLocationData[pid][1] = position[1]
                            vertexNumericLocationData[pid][2] = position[2]

                        pid += 1

                    if normalData:
                        normal = self.fMeshGeom.normals[self.fMeshGeom.face_connects[vid]]
                        normalData[nid][0] = normal[0]
                        normalData[nid][1] = normal[1]
                        normalData[nid][2] = normal[2]

                        nid += 1

                    if uvData:
                        uv = [0, 0]
                        if numUVs > 0:
                            uvNum = self.fMeshGeom.uvcoords.uvId(vid)
                            uv = self.fMeshGeom.uvcoords.getUV(uvNum)
                        uvData[uvid][0] = uv[0]
                        uvData[uvid][1] = uv[0]

                        uvid += 1

                    ## Just same fake colors to show filling in requirements for
                    ## color-per-vertex (CPV)
                    if cpvData:
                        position = self.fMeshGeom.vertices[self.fMeshGeom.face_connects[vid]]
                        cpvData[cid][0] = position[0]
                        cpvData[cid][1] = position[1]
                        cpvData[cid][2] = position[2]
                        cpvData[cid][3] = 1.0

                        cid += 1

                    ## Vertex id's used for numeric display
                    if vertexNumericIdData:
                        vertexNumericIdData[vid] = (ctypes.c_float * 1)(self.fMeshGeom.face_connects[vid])
                        pass

                    vid += 1

            elif numVerts > 0:
                vid += numVerts

        if positionDataAddress:
            positionBuffer.commit(positionDataAddress)

        if normalDataAddress:
            normalBuffer.commit(normalDataAddress)

        if uvDataAddress:
            uvBuffer.commit(uvDataAddress)

        if cpvDataAddress:
            cpvBuffer.commit(cpvDataAddress)
        
        if vertexNumericIdDataAddress:
            vertexNumericIdBuffer.commit(vertexNumericIdDataAddress)

        if vertexNumericIdPositionDataAddress:
            vertexNumericIdPositionBuffer.commit(vertexNumericIdPositionDataAddress)

        if vertexNumericLocationDataAddress:
            vertexNumericLocationBuffer.commit(vertexNumericLocationDataAddress)

        if vertexNumericLocationPositionDataAddress:
            vertexNumericLocationPositionBuffer.commit(vertexNumericLocationPositionDataAddress)

        ## Fill in active vertex data buffer (only when fDrawSharedActiveVertices=True
        ## which results in activeVertexPositionDataAddress and activeVertexPositionBuffer being non-NULL)
        ##
        if activeVertexPositionData:
            if debugPopulateGeometry:
                print(">>> Fill in the data for active vertex position buffer base on component list")

            ## Fill in position buffer with positions based on active vertex indexing list
            ##
            if activeVertexCount > len(self.fMeshGeom.vertices):
                activeVertexCount = len(self.fMeshGeom.vertices)

            for i in range(activeVertexCount):
                position = self.fMeshGeom.vertices[ self.fActiveVertices[i] ]
                activeVertexPositionData[i][0] = position[0]
                activeVertexPositionData[i][1] = position[1]
                activeVertexPositionData[i][2] = position[2]

            activeVertexPositionBuffer.commit(activeVertexPositionDataAddress)

        if activeVertexUVData:
            if debugPopulateGeometry:
                print(">>> Fill in the data for active vertex uv buffer base on component list")

            ## Fill in position buffer with positions based on active vertex indexing list
            ##
            if activeVertexCount > len(self.fMeshGeom.vertices):
                activeVertexCount = len(self.fMeshGeom.vertices)

            for i in range(activeVertexCount):
                activeVertexUVData[i] = i // activeVertexCount

            activeVertexUVBuffer.commit(activeVertexUVDataAddress)

        ## Fill in face center data buffer (only when fDrawFaceCenter=True
        ## which results in faceCenterPositionDataAddress and faceCenterPositionBuffer being non-NULL)
        ##
        if faceCenterPositionData:
            if debugPopulateGeometry:
                print(">>> Fill in the data for face center position buffer")

            ## Fill in face center buffer with positions based on realtime calculations.
            ##
            pid = 0
            vid = 0
            for faceId in range(self.fMeshGeom.faceCount):
                ##tmp variables for calculating the face center position.
                x = 0.0
                y = 0.0
                z = 0.0

                faceCenterPosition = om.MPoint()

                ## ignore degenerate faces
                numVerts = self.fMeshGeom.face_counts[faceId]
                if numVerts > 2:
                    for v in range(numVerts):
                        face_vertex_position = self.fMeshGeom.vertices[self.fMeshGeom.face_connects[vid]]
                        x += face_vertex_position[0]
                        y += face_vertex_position[1]
                        z += face_vertex_position[2]

                        vid += 1

                    faceCenterPosition = om.MPoint(x, y, z) / numVerts

                elif numVerts > 0:
                    vid += numVerts

                faceCenterPositionData[faceId][0] = faceCenterPosition[0]
                faceCenterPositionData[faceId][1] = faceCenterPosition[1]
                faceCenterPositionData[faceId][2] = faceCenterPosition[2]

            faceCenterPositionBuffer.commit(faceCenterPositionDataAddress)

        ## Run around a second time and handle duplicate buffers and unknown buffers
        ##
        for i in range(len(descList)):
            if satisfiedRequirements[i]:
                continue
            desc = descList[i]
            if self.fDrawSharedActiveVertices and (desc.name == self.sActiveVertexStreamName):
                if desc.semantic == omr.MGeometry.kPosition:
                    satisfiedRequirements[i] = True
                    self.cloneVertexBuffer(activeVertexPositionBuffer, data, desc, activeVertexCount, debugPopulateGeometry)
                elif desc.semantic == omr.MGeometry.kTexture:
                    satisfiedRequirements[i] = True
                    self.cloneVertexBuffer(activeVertexUVBuffer, data, desc, activeVertexCount, debugPopulateGeometry)
            elif self.fDrawFaceCenters and desc.name == self.sFaceCenterStreamName:
                if desc.semantic == omr.MGeometry.kPosition:
                    satisfiedRequirements[i] = True
                    self.cloneVertexBuffer(faceCenterPositionBuffer, data, desc, self.fMeshGeom.faceCount, debugPopulateGeometry)
            else:
                if desc.semantic == omr.MGeometry.kPosition:
                    if desc.name == self.sVertexIdItemName:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(vertexNumericIdPositionBuffer, data, desc, totalVerts, debugPopulateGeometry)
                    elif desc.name == self.sVertexPositionItemName:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(vertexNumericLocationPositionBuffer, data, desc, totalVerts, debugPopulateGeometry)
                    else:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(positionBuffer, data, desc, totalVerts, debugPopulateGeometry)
                elif desc.semantic == omr.MGeometry.kNormal:
                    satisfiedRequirements[i] = True
                    self.cloneVertexBuffer(normalBuffer, data, desc, totalVerts, debugPopulateGeometry)
                elif desc.semantic == omr.MGeometry.kTexture:
                    numericValue = "numericvalue"
                    numeric3Value ="numeric3value"
                    if desc.semanticName.lower() == numericValue and desc.name == self.sVertexIdItemName:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(vertexNumericIdBuffer, data, desc, totalVerts, debugPopulateGeometry)
                    elif desc.semanticName.lower() == numeric3Value and desc.name == self.sVertexPositionItemName:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(vertexNumericLocationBuffer, data, desc, totalVerts, debugPopulateGeometry)
                    elif desc.name != self.sVertexIdItemName and desc.name != self.sVertexPositionItemName:
                        satisfiedRequirements[i] = True
                        self.cloneVertexBuffer(uvBuffer, data, desc, totalVerts, debugPopulateGeometry)
                elif desc.semantic == omr.MGeometry.kColor:
                    satisfiedRequirements[i] = True
                    self.cloneVertexBuffer(cpvBuffer, data, desc, totalVerts, debugPopulateGeometry)
            
            if not satisfiedRequirements[i]:
                ## We have a strange buffer request we do not understand. Provide a set of Zeros sufficient to cover
                ## totalVerts:
                destBuffer = data.createVertexBuffer(desc)
                if destBuffer:
                    satisfiedRequirements[i] = True
                    if debugPopulateGeometry:
                        print(">>> Fill in dummy requirement '%s'" % (desc.name, ))
                    destBufferDataAddress = destBuffer.acquire(totalVerts, True) ## writeOnly - we don't need the current buffer values
                    if destBufferDataAddress:
                        destBufferData = ((ctypes.c_float * desc.dimension)*totalVerts).from_address(destBufferDataAddress)
                        if destBufferData:
                            for j in range(totalVerts):
                                if desc.dimension == 4:
                                    destBufferData[j] = (1.0, 0.0, 0.0, 1.0)
                                elif desc.dimension == 3:
                                    destBufferData[j] = (1.0, 0.0, 0.0)
                                else:
                                    for k in range(desc.dimension):
                                        destBufferData[j][k] = 0.0
                        destBuffer.commit(destBufferDataAddress)

    ##  Clone a vertex buffer to fulfill a duplicate requirement.
    ##  Can happen for effects asking for multiple UV streams by
    ##  name.
    def cloneVertexBuffer(self, srcBuffer, data, desc, dataSize, debugPopulateGeometry):
        if srcBuffer:
            destBuffer = data.createVertexBuffer(desc)
            if destBuffer:
                if debugPopulateGeometry:
                    print(">>> Cloning requirement '%s'" % (desc.name, ))
                destBufferDataAddress = destBuffer.acquire(dataSize, True) ## writeOnly - we don't need the current buffer values
                srcBufferDataAddress = srcBuffer.map()
                if destBufferDataAddress and srcBufferDataAddress:
                    destBufferData = ((ctypes.c_float * desc.dimension)*dataSize).from_address(destBufferDataAddress)
                    srcBufferData = ((ctypes.c_float * desc.dimension)*dataSize).from_address(srcBufferDataAddress)
                    if destBufferData and srcBufferData:
                        for j in range(dataSize):
                            for k in range(desc.dimension):
                                destBufferData[j][k] = srcBufferData[j][k]
                    destBuffer.commit(destBufferDataAddress)
                srcBuffer.unmap()

    ## Indexing for render item handling methods
    def updateIndexingForWireframeItems(self, wireIndexBuffer, item, data, totalVerts):
        ## Create / update indexing required to draw wireframe render items.
        ## There can be more than one render item using the same wireframe indexing
        ## so it is passed in as an argument. If it is not null then we can
        ## reuse it instead of creating new indexing.
    
        ## Wireframe index buffer is same for both wireframe and selected render item
        ## so we only compute and allocate it once, but reuse it for both render items
        if not wireIndexBuffer:
            wireIndexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
            if wireIndexBuffer:
                dataAddress = wireIndexBuffer.acquire(2*totalVerts, True) ## writeOnly - we don't need the current buffer values
                if dataAddress:
                    data = (ctypes.c_uint * (2*totalVerts)).from_address(dataAddress)
                    vid = 0
                    first = 0
                    idx = 0
                    for faceIdx in range(self.fMeshGeom.faceCount):
                        ## ignore degenerate faces
                        numVerts = self.fMeshGeom.face_counts[faceIdx]
                        if numVerts > 2:
                            first = vid
                            for v in range(numVerts-1):
                                data[idx] = vid
                                vid += 1
                                idx += 1
                                data[idx] = vid
                                idx += 1

                            data[idx] = vid
                            vid += 1
                            idx += 1
                            data[idx] = first
                            idx += 1

                        else:
                            vid += numVerts

                    wireIndexBuffer.commit(dataAddress)

        ## Associate same index buffer with either render item
        if wireIndexBuffer:
            item.associateWithIndexBuffer(wireIndexBuffer)

    def updateIndexingForDormantVertices(self, item, data, numTriangles):
        ## Create / update indexing for render items which draw dormant vertices

        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            dataAddress = indexBuffer.acquire(3*numTriangles, True) ## writeOnly - we don't need the current buffer values
            if dataAddress:
                data = (ctypes.c_uint*(3*numTriangles)).from_address(dataAddress)
                ## compute index data for triangulated convex polygons sharing
                ## poly vertex data among triangles
                base = 0
                idx = 0
                for faceIdx in range(self.fMeshGeom.faceCount):
                    ## ignore degenerate faces
                    numVerts = self.fMeshGeom.face_counts[faceIdx]
                    if numVerts > 2:
                        for v in range(1, numVerts-1):
                            data[idx] = base
                            data[idx+1] = base+v
                            data[idx+2] = base+v+1
                            idx += 3

                        base += numVerts

                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

    def updateIndexingForFaceCenters(self, item, data, debugPopulateGeometry):
        ## Create / update indexing for render items which draw face centers

        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            dataAddress = indexBuffer.acquire(self.fMeshGeom.faceCount, True) ## writeOnly - we don't need the current buffer values
            if dataAddress:
                data = (ctypes.c_uint * self.fMeshGeom.faceCount).from_address(dataAddress)
                if debugPopulateGeometry:
                    print(">>> Set up indexing for face centers")

                for i in range(self.fMeshGeom.faceCount):
                    data[i] = 0
                    pass

                idx = 0
                for i in range(self.fMeshGeom.faceCount):
                    ## ignore degenerate faces
                    numVerts = self.fMeshGeom.face_counts[i]
                    if numVerts > 2:
                        data[idx] = idx
                        idx += 1

                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

    def updateIndexingForVertices(self, item, data, numTriangles, activeVertexCount, debugPopulateGeometry):
        ## Create / update indexing for render items which draw active vertices

        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            dataAddress = None

            ## If drawing shared active vertices then the indexing degenerates into
            ## a numerically increasing index value. Otherwise a remapping from
            ## the active vertex list indexing to the unshared position stream is required.
            ##
            ## 1. Create indexing for shared positions. In this case it
            ## is a degenerate list since the position buffer was created
            ## in linear ascending order.
            ##
            if self.fDrawSharedActiveVertices:
                dataAddress = indexBuffer.acquire(activeVertexCount, True) ## writeOnly - we don't need the current buffer values
                if dataAddress:
                    data = (ctypes.c_uint*activeVertexCount).from_address(dataAddress)
                    if debugPopulateGeometry:
                        print(">>> Set up indexing for shared vertices")

                    for i in range(activeVertexCount):
                        data[i] = i

            ## 2. Create indexing to remap to unshared positions
            ##
            else:
                if debugPopulateGeometry:
                    print(">>> Set up indexing for unshared vertices")

                vertexCount = 3*numTriangles
                dataAddress = indexBuffer.acquire(vertexCount, True) ## writeOnly - we don't need the current buffer values
                if dataAddress:
                    data = (ctypes.c_uint*vertexCount).from_address(dataAddress)
                    for i in range(vertexCount):
                        data[i] = vertexCount+1

                    selectionIdSet = self.fActiveVerticesSet

                    ## compute index data for triangulated convex polygons sharing
                    ## poly vertex data among triangles
                    base = 0
                    lastFound = 0
                    idx = 0
                    for faceIdx in range(self.fMeshGeom.faceCount):
                        ## ignore degenerate faces
                        numVerts = self.fMeshGeom.face_counts[faceIdx]
                        if numVerts > 2:
                            for v in range(1, numVerts-1):
                                vertexId = self.fMeshGeom.face_connects[base]
                                if vertexId in selectionIdSet:
                                    lastFound = base
                                    data[idx] = lastFound
                                    idx += 1

                                vertexId = self.fMeshGeom.face_connects[base+v]
                                if vertexId in selectionIdSet:
                                    lastFound = base+v
                                    data[idx] = lastFound
                                    idx += 1

                                vertexId = self.fMeshGeom.face_connects[base+v+1]
                                if vertexId in selectionIdSet:
                                    lastFound = base+v+1
                                    data[idx] = lastFound
                                    idx +1

                            base += numVerts

                    for i in range(vertexCount):
                        if data[i] == vertexCount+1:
                            data[i] = lastFound

            if dataAddress:
                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

    def updateIndexingForEdges(self, item, data, totalVerts, fromSelection):
        ## Create / update indexing for render items which draw affected edges

        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            totalEdges = 2*totalVerts
            totalEdgesP1 = 2*totalVerts+1
            dataAddress = indexBuffer.acquire(totalEdges, True) ## writeOnly - we don't need the current buffer values
            if dataAddress:
                data = (ctypes.c_uint*totalEdges).from_address(dataAddress)
                for i in range(totalEdges):
                    data[i] = totalEdgesP1
                    pass

                displayAll = not fromSelection
                displayActives = (not displayAll and bool(self.fActiveEdgesSet))
                displayAffected = (not displayAll and not displayActives)

                selectionIdSet = None
                if displayActives:
                    selectionIdSet = self.fActiveEdgesSet
                elif displayAffected:
                    selectionIdSet = self.fActiveVerticesSet

                base = 0
                lastFound = 0
                idx = 0
                edgeId = 0
                for faceIdx in range(self.fMeshGeom.faceCount):
                    ## ignore degenerate faces
                    numVerts = self.fMeshGeom.face_counts[faceIdx]
                    if numVerts > 2:
                        for v in range(numVerts):
                            enableEdge = displayAll
                            vindex1 = base + (v % numVerts)
                            vindex2 = base + ((v+1) % numVerts)

                            if displayAffected:
                                ## Check either ends of an "edge" to see if the
                                ## vertex is in the active vertex list
                                ##
                                vertexId = self.fMeshGeom.face_connects[vindex1]
                                if vertexId in selectionIdSet:
                                    enableEdge = True
                                    lastFound = vindex1

                                if not enableEdge:
                                    vertexId2 = self.fMeshGeom.face_connects[vindex2]
                                    if vertexId2 in selectionIdSet:
                                        enableEdge = True
                                        lastFound = vindex2

                            elif displayActives:
                                ## Check if the edge is active
                                ##
                                if edgeId in selectionIdSet:
                                    enableEdge = True
                                    lastFound = vindex1

                            ## Add indices for "edge"
                            if enableEdge:
                                data[idx] = vindex1
                                idx += 1
                                data[idx] = vindex2
                                idx += 1
                            edgeId += 1

                        base += numVerts

                if not displayAll:
                    for i in range(totalEdges):
                        if data[i] == totalEdgesP1:
                            data[i] = lastFound

                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

    def updateIndexingForFaces(self, item, data, numTriangles, fromSelection):
        ## Create / update indexing for render items which draw affected/active faces

        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            numTriangleVertices = 3*numTriangles
            dataAddress = indexBuffer.acquire(numTriangleVertices, True) ## writeOnly - we don't need the current buffer values
            if dataAddress:
                data = (ctypes.c_uint*numTriangleVertices).from_address(dataAddress)
                for i in range(numTriangleVertices):
                    data[i] = numTriangleVertices+1
                    pass

                displayAll = not fromSelection
                displayActives = (not displayAll and bool(self.fActiveFacesSet))
                displayAffected = (not displayAll and not displayActives)
                isolateSelect = item.isIsolateSelectCopy()
                
                enableFaces = []
                if(isolateSelect):
                    enableFaces = [0] * self.fMeshGeom.faceCount
                    
                    for i in range(self.fMeshGeom.faceCount):
                        enableFaces[i] = False


                    fnComponent = om.MFnSingleIndexedComponent( item.shadingComponent() )
                    if(fnComponent.componentType == om.MFn.kMeshPolygonComponent):
                        faceIds = fnComponent.getElements()
                        
                        for i in range(len(faceIds)):
                            enableFaces[faceIds[i]] = True


                selectionIdSet = None
                if displayActives:
                    selectionIdSet = self.fActiveFacesSet
                elif displayAffected:
                    selectionIdSet = self.fActiveVerticesSet

                base = 0
                lastFound = 0
                idx = 0
                for faceIdx in range(self.fMeshGeom.faceCount):
                    ## ignore degenerate faces
                    numVerts = self.fMeshGeom.face_counts[faceIdx]
                    if numVerts > 2:
                        enableFace = False

                        if displayAffected:
                            ## Scan for any vertex in the active list
                            ##
                            for v in range(1, numVerts-1):
                                vertexId = self.fMeshGeom.face_connects[base]
                                if vertexId in selectionIdSet:
                                    enableFace = True
                                    lastFound = base

                                if not enableFace:
                                    vertexId2 = self.fMeshGeom.face_connects[base+v]
                                    if vertexId2 in selectionIdSet:
                                        enableFace = True
                                        lastFound = base+v

                                if not enableFace:
                                    vertexId3 = self.fMeshGeom.face_connects[base+v+1]
                                    if vertexId3 in selectionIdSet:
                                        enableFace = True
                                        lastFound = base+v+1

                        elif displayActives:
                            if (not isolateSelect or enableFaces[faceIdx]):
                                ## Check if the face is active
                                ##
                                if faceIdx in selectionIdSet:
                                    enableFace = True
                                    lastFound = base
                        elif (not isolateSelect or enableFaces[faceIdx]):
                            enableFace = True
                            lastFound  = base
                        
                        
                        ## Found an active face
                        ## or one active vertex on the triangle so add indexing for the entire triangle.
                        ##
                        if enableFace:
                            for v in range(1, numVerts-1):
                                data[idx] = base
                                data[idx+1] = base+v
                                data[idx+2] = base+v+1
                                idx += 3

                        base += numVerts

                if not displayAll:
                    for i in range(numTriangleVertices):
                        if data[i] == numTriangleVertices+1:
                            data[i] = lastFound

                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

    def updateIndexingForShadedTriangles(self, item, data, numTriangles):
        ## Create / update indexing for render items which draw filled / shaded
        ## triangles.
        
        indexBuffer = data.createIndexBuffer(omr.MGeometry.kUnsignedInt32)
        if indexBuffer:
            isolateSelect = item.isIsolateSelectCopy()
            
            enableFaces = []
            if (isolateSelect):
                enableFaces = [0] * self.fMeshGeom.faceCount
                
                for i in range(self.fMeshGeom.faceCount):
                    enableFaces[i] = False

                fnComponent = om.MFnSingleIndexedComponent( item.shadingComponent() )
                if(fnComponent.componentType == om.MFn.kMeshPolygonComponent):
                    faceIds = fnComponent.getElements()
                    
                    for i in range(len(faceIds)):
                        enableFaces[faceIds[i]] = True
            
            indices = [0] * numTriangles * 3
            
            base = 0
            idx = 0
            for faceIdx in range(self.fMeshGeom.faceCount):
                ## ignore degenerate faces
                numVerts = self.fMeshGeom.face_counts[faceIdx]
                if numVerts > 2:
                    if (not isolateSelect or enableFaces[faceIdx]):
                        for v in range(1, numVerts-1):
                            indices[idx] = base
                            indices[idx+1] = base+v
                            indices[idx+2] = base+v+1
                            idx += 3
                    base += numVerts
            
            dataAddress = indexBuffer.acquire(len(indices), True) ## writeOnly - we don't need the current buffer values
            if dataAddress:
                data = (ctypes.c_uint * len(indices)).from_address(dataAddress)
                
                for i in range(len(indices)):
                    data[i] = indices[i]
                
                indexBuffer.commit(dataAddress)

            item.associateWithIndexBuffer(indexBuffer)

################################################################################
##
## Node registry
##
## Registers/Deregisters apiMeshData geometry data,
## apiMeshCreator DG node, and apiMeshShape user defined shape.
##
################################################################################



def initializePlugin(obj):
    plugin = om.MFnPlugin(obj, "Autodesk", "3.0", "Any")

    try:
        plugin.registerData("apiMeshData_py", apiMeshData.id, apiMeshData.creator, om.MPxData.kGeometryData)
    except:
        sys.stderr.write("Failed to register data\n")
        raise

    try:
        plugin.registerShape("apiMesh_py", apiMeshGeometryShape.id, apiMeshGeometryShape.creator, apiMeshGeometryShape.initialize, apiMeshUI.creator, apiMeshGeometryShape.sDrawDbClassification)
    except:
        sys.stderr.write("Failed to register node\n")
        raise

    try:
        plugin.registerShape("apiMeshSubscene_py", apiMeshSubsceneShape.id, apiMeshSubsceneShape.creator, apiMeshSubsceneShape.initialize, apiMeshUI.creator, apiMeshSubsceneShape.sDrawDbClassification)
    except:
        sys.stderr.write("Failed to register node\n")
        raise

    try:
        plugin.registerNode("apiMeshCreator_py", apiMeshCreator.id, apiMeshCreator.creator, apiMeshCreator.initialize)
    except:
        sys.stderr.write("Failed to register node\n")
        raise

    try:
        omr.MDrawRegistry.registerGeometryOverrideCreator(apiMeshGeometryShape.sDrawDbClassification, apiMesh.sDrawRegistrantId, apiMeshGeometryOverride.creator)
    except:
        sys.stderr.write("Failed to register override\n")
        raise

    try:
        omr.MDrawRegistry.registerSubSceneOverrideCreator(apiMeshSubsceneShape.sDrawDbClassification, apiMesh.sDrawRegistrantId, apiMeshSubSceneOverride.creator)
    except:
        sys.stderr.write("Failed to register override\n")
        raise

    try:
        omr.MDrawRegistry.registerComponentConverter(apiMeshGeometryOverride.sVertexItemName, meshVertComponentConverterGeometryOverride.creator)
        omr.MDrawRegistry.registerComponentConverter(apiMeshGeometryOverride.sEdgeSelectionItemName, meshEdgeComponentConverterGeometryOverride.creator)
        omr.MDrawRegistry.registerComponentConverter(apiMeshGeometryOverride.sFaceSelectionItemName, meshFaceComponentConverterGeometryOverride.creator)
    except:
        sys.stderr.write("Failed to register component converters\n")
        raise

    try:
        omr.MDrawRegistry.registerComponentConverter(apiMeshSubSceneOverride.sVertexSelectionName, simpleComponentConverterSubsceneOverride.creatorVertexSelection)
        omr.MDrawRegistry.registerComponentConverter(apiMeshSubSceneOverride.sEdgeSelectionName, simpleComponentConverterSubsceneOverride.creatorEdgeSelection)
        omr.MDrawRegistry.registerComponentConverter(apiMeshSubSceneOverride.sFaceSelectionName, simpleComponentConverterSubsceneOverride.creatorFaceSelection)
    except:
        sys.stderr.write("Failed to register component converters\n")
        raise

def uninitializePlugin(obj):
    plugin = om.MFnPlugin(obj)

    omr.MDrawRegistry.deregisterComponentConverter(apiMeshSubSceneOverride.sVertexSelectionName)
    omr.MDrawRegistry.deregisterComponentConverter(apiMeshSubSceneOverride.sEdgeSelectionName)
    omr.MDrawRegistry.deregisterComponentConverter(apiMeshSubSceneOverride.sFaceSelectionName)
    
    ## Deregister component converter for isolate select render items
    for faceSelectionName in sViewSelectedFaceSelectionNames:
        omr.MDrawRegistry.deregisterComponentConverter(faceSelectionName)


    omr.MDrawRegistry.deregisterComponentConverter(apiMeshGeometryOverride.sVertexItemName)
    omr.MDrawRegistry.deregisterComponentConverter(apiMeshGeometryOverride.sEdgeSelectionItemName)
    omr.MDrawRegistry.deregisterComponentConverter(apiMeshGeometryOverride.sFaceSelectionItemName)

    try:
        omr.MDrawRegistry.deregisterGeometryOverrideCreator(apiMeshGeometryShape.sDrawDbClassification, apiMesh.sDrawRegistrantId)
    except:
        sys.stderr.write("Failed to deregister override\n")
        pass
        
    try:
        omr.MDrawRegistry.deregisterSubSceneOverrideCreator(apiMeshSubsceneShape.sDrawDbClassification, apiMesh.sDrawRegistrantId)
    except:
        sys.stderr.write("Failed to deregister override\n")
        pass

    try:
        plugin.deregisterNode(apiMeshCreator.id)
    except:
        sys.stderr.write("Failed to deregister node\n")
        pass

    try:
        plugin.deregisterNode(apiMeshSubsceneShape.id)
    except:
        sys.stderr.write("Failed to deregister node\n")
        pass

    try:
        plugin.deregisterNode(apiMeshGeometryShape.id)
    except:
        sys.stderr.write("Failed to deregister node\n")
        pass

    try:
        plugin.deregisterData(apiMeshData.id)
    except:
        sys.stderr.write("Failed to deregister data\n")
        pass