scripted/splitUVCmd.py

#-
# ==========================================================================
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#+

########################################################################
# DESCRIPTION:
#
# Produces the Python command "spSplitUV". 
#
# The splitUV command unshares or "splits" the selected UVs of a polygonal mesh.
# It is also a good example of how to write poly operation nodes that properly
# deal with history, tweaks, and so on. 
#
# For a thorough explanation of creating this command, refer to the "splitUVCmd example"
# topic in the Polygon API section of the online help. Note that the example in the
# online help uses a MEL script for demonstration. Refer to this splitUVCmd.py script
# for a Python version of the example. 
#
# How it works:
#
# This command is based on the polyModifierCmd. It relies on the polyModifierCmd
# to manage "how" the effects of the splitUV operation are applied (directly
# on the mesh or through a modifier node). See polyModifier.py for more details.
#
# To understand the algorithm behind the splitUV operation, refer to splitUVFty.
#
# Limitations:
#
# It can only operate on a single mesh at a given time. If there is more than one
# mesh with selected UVs, it operates only on the first mesh found in the selection list.
#
########################################################################

import maya.OpenMaya as OpenMaya
import maya.OpenMayaMPx as OpenMayaMPx
import sys

import polyModifier

def statusError(message):
    fullMsg = "Status failed: %s\n" % message
    sys.stderr.write(fullMsg)
    OpenMaya.MGlobal.displayError(fullMsg)
    raise   # called from exception handlers only, reraise exception


kPluginCmdName = "spSplitUV"
kPluginNodeTypeName = "spSplitUVNode"
kPluginNodeId = OpenMaya.MTypeId(0x87013)

class splitUV(polyModifier.polyModifierCmd):
    def __init__(self):
        polyModifier.polyModifierCmd.__init__(self)
        # Selected UVs
        #
        # Note: The MObject, fComponentList, is only ever accessed on a single call to the plugin.
        #        It is never accessed between calls and is stored on the class for access in the
        #        overriden initModifierNode() method.
        #
        self.__fComponentList = OpenMaya.MObject()
        self.__fSelUVs = OpenMaya.MIntArray()
        self.__fSplitUVFactory = splitUVFty()


    def isUndoable(self):
        return True


    def doIt(self, args):
        """
        implements the scripted splitUV command.

        Arguments:
            args - the argument list that was passes to the command from MEL
        """
        # Parse the selection list for objects with selected UV components.
        # To simplify things, we only take the first object that we find with
        # selected UVs and operate on that object alone.
        #
        # All other objects are ignored and return warning messages indicating
        # this limitation.
        #
        selList = OpenMaya.MSelectionList()
        OpenMaya.MGlobal.getActiveSelectionList(selList)
        selListIter = OpenMaya.MItSelectionList(selList)

        # The splitUV node only accepts a component list input, so we build
        # a component list using MFnComponentListData.
        #
        # MIntArrays could also be passed into the node to represent the uvIds,
        # but are less storage efficient than component lists, since consecutive 
        # components are bundled into a single entry in component lists.
        #
        compListFn = OpenMaya.MFnComponentListData()
        compListFn.create()
        found = False
        foundMultiple = False

        while not selListIter.isDone():
            dagPath = OpenMaya.MDagPath()
            component = OpenMaya.MObject()
            itemMatches = True
            selListIter.getDagPath(dagPath, component)

            # Check for selected UV components
            #
            if itemMatches and (component.apiType() == OpenMaya.MFn.kMeshMapComponent):
                if not found:  
                    # The variable 'component' holds all selected components on the selected
                    # object, thus only a single call to MFnComponentListData::add() is needed
                    # to store the selected components for a given object.
                    #
                    compListFn.add(component)

                    # Copy the component list created by MFnComponentListData into our local
                    # component list MObject member.
                    #
                    self.__fComponentList = compListFn.object()

                    # Locally store the actual uvIds of the selected UVs so that this command
                    # can directly modify the mesh in the case when there is no history and
                    # history is turned off.
                    #
                    compFn = OpenMaya.MFnSingleIndexedComponent(component)
                    compFn.getElements(self.__fSelUVs)

                    # Ensure that this DAG path will point to the shape of our object.
                    # Set the DAG path for the polyModifierCmd.
                    #
                    dagPath.extendToShape()
                    self._setMeshNode(dagPath)
                    found = True
                else:
                    # Break once we have found a multiple object holding selected UVs, since
                    # we are not interested in how many multiple objects there are, only
                    # the fact that there are multiple objects.
                    #
                    foundMultiple = True
                    break

            selListIter.next()

        if foundMultiple:
            self.displayWarning("Found more than one object with selected UVs - Only operating on first found object.")

        # Initialize the polyModifierCmd node type - mesh node already set
        #
        self._setModifierNodeType(kPluginNodeId)

        if found:
            if self.__validateUVs():
                # Now, pass control over to the polyModifierCmd._doModifyPoly() method
                # to handle the operation.
                #
                try:
                    self._doModifyPoly()
                except:
                    self.displayError("splitUV command failed!")
                    raise
                else:
                    self.setResult("splitUV command succeeded!")
            else:
                self.displayError("splitUV command failed: Selected UVs are not splittable")
        else:
            self.displayError("splitUV command failed: Unable to find selected UVs")


    def redoIt(self):
        """
        Implements redo for the scripted splitUV command. 

        This method is called when the user has undone a command of this type
        and then redoes it.  No arguments are passed in as all of the necessary
        information is cached by the doIt method.
        """
        try:
            self._redoModifyPoly()
            self.setResult("splitUV command succeeded!")
        except:
            self.displayError("splitUV command failed!")
            raise


    def undoIt(self):
        """
        implements undo for the scripted splitUV command.  

        This method is called to undo a previous command of this type.  The 
        system should be returned to the exact state that it was it previous 
        to this command being executed.  That includes the selection state.
        """
        try:
            self._undoModifyPoly()
            self.setResult("splitUV undo succeeded!")
        except:
            self.displayError("splitUV undo failed!")
            raise


    def _initModifierNode(self, modifierNode):
        # We need to tell the splitUV node which UVs to operate on. By overriding
        # the polyModifierCmd._initModifierNode() method, we can insert our own
        # modifierNode initialization code.
        #
        depNodeFn = OpenMaya.MFnDependencyNode(modifierNode)
        uvListAttr = depNodeFn.attribute("inputComponents")

        # Pass the component list down to the splitUV node
        #
        uvListPlug = OpenMaya.MPlug(modifierNode, uvListAttr)
        uvListPlug.setMObject(self.__fComponentList)


    def _directModifier(self, mesh):
        self.__fSplitUVFactory.setMesh(mesh)
        self.__fSplitUVFactory.setUVIds(self.__fSelUVs)

        # Now, perform the splitUV
        #
        self.__fSplitUVFactory.doIt()


    def __validateUVs(self):
        """
        Validate the UVs for the splitUV operation. UVs are valid only if they are shared
        by more than one face. While the splitUVNode is smart enough to not process the
        split if a UV is not splittable, a splitUV node is still created by the polyModifierCmd.
        So call this method to validate the UVs before calling _doModifyPoly().

        validateUVs() will return true so long as there is at least one valid UV. It will
        also prune out any invalid UVs from both the component list and UVId array.
        """
        # Get the mesh that we are operating on
        #
        dagPath = self._getMeshNode()
        mesh = dagPath.node()

        # Get the number of faces sharing the selected UVs
        #
        meshFn = OpenMaya.MFnMesh(mesh)
        polyIter = OpenMaya.MItMeshPolygon(mesh)
        selUVFaceCountArray = OpenMaya.MIntArray()

        indexParam = OpenMaya.MScriptUtil(0)
        indexPtr = indexParam.asIntPtr()

        count = 0
        selUVsCount = self.__fSelUVs.length()
        for i in range(selUVsCount):
            while not polyIter.isDone():
                if polyIter.hasUVs():
                    polyVertCount = polyIter.polygonVertexCount()

                    for j in range(polyVertCount):
                        polyIter.getUVIndex(j, indexPtr)
                        UVIndex = indexParam.getInt(indexPtr)

                        if UVIndex == self.__fSelUVs[i]:
                            count += 1
                            break
                polyIter.next()
            selUVFaceCountArray.append(count)

        # Now, check to make sure that at least one UV is being shared by more than one
        # face. So long as we have one UV that we can operate on, we should proceed and let
        # the splitUVNode ignore the UVs which are only shared by one face.
        #
        isValid = False
        validUVIndices = OpenMaya.MIntArray()

        for i in range(selUVsCount):
            if selUVFaceCountArray[i] > 1:
                isValid = True
                validUVIndices.append(i)

        if isValid:
            self.__pruneUVs(validUVIndices)

        return isValid


    def __pruneUVs(self, validUVIndices):
        """
        This method will remove any invalid UVIds from the component list and UVId array.
        The benefit of this is to reduce the amount of extra processing that the node would
        have to perform. It will result in less iterations through the mesh as there are
        less UVs to search for.
        """
        validUVIds = OpenMaya.MIntArray()

        for i in range(validUVIndices.length()):
            uvIndex = validUVIndices[i]
            validUVIds.append(self.__fSelUVs[uvIndex])

        # Replace the local int array of UVIds
        #
        self.__fSelUVs.clear()
        self.__fSelUVs = validUVIds

        # Build the list of valid components
        #
        compFn = OpenMaya.MFnSingleIndexedComponent()
        try:
            compFn.create(OpenMaya.MFn.kMeshMapComponent)
        except:
            statusError("compFn.create( MFn::kMeshMapComponent )")
        
        try:
            compFn.addElements(validUVIds)
        except:
            statusError("compFn.addElements( validUVIds )")
        
        # Replace the component list
        #
        component = compFn.object()
        compListFn = OpenMaya.MFnComponentListData()
        compListFn.create()
        try:
            compListFn.add(component)
        except:
            statusError("compListFn.add( component )")

        self.__fComponentList = compListFn.object()


#####################################################################
## FACTORY ##########################################################
#####################################################################

# Overview:
#
#       The splitUV factory implements the actual splitUV operation. It takes in
#       only two parameters:
#
#           1) A polygonal mesh
#           2) An array of selected UV Ids
#
#       The algorithm works as follows:
#
#           1) Parse the mesh for the selected UVs and collect:
#
#               (a) Number of faces sharing each UV
#                   (stored as two arrays: face array, indexing/offset array)
#               (b) Associated vertex Id
#
#           2) Create (N-1) new UVIds for each selected UV, where N represents the number of faces
#              sharing the UV.
#
#           3) Set each of the new UVs to the same 2D location on the UVmap.
#
#           3) Arbitrarily let the last face in the list of faces sharing this UV to keep the original
#              UV.
#
#           4) Assign each other face one of the new UVIds.
#
#
class splitUVFty(polyModifier.polyModifierFty):
    def __init__(self):
        polyModifier.polyModifierFty.__init__(self)
        # Mesh Node
        # Note: We only make use of this MObject during a single call of
        #       the splitUV plugin. It is never maintained and used between
        #       calls to the plugin as the MObject handle could be invalidated
        #       between calls to the plugin.
        #
        self.__fMesh = OpenMaya.MObject()
        self.__fSelUVs = OpenMaya.MIntArray()
        self.__fSelUVs.clear()


    def setMesh(self, mesh):
        self.__fMesh = mesh


    def setUVIds(self, uvIds):
        self.__fSelUVs = uvIds


    def doIt(self):
        """
        Performs the actual splitUV operation on the given object and UVs
        """
        ####################################
        # Declare our processing variables #
        ####################################

        # Face Id and Face Offset map to the selected UVs
        #
        selUVFaceIdMap = OpenMaya.MIntArray()
        selUVFaceOffsetMap = OpenMaya.MIntArray()

        # Local Vertex Index map to the selected UVs
        #
        selUVLocalVertIdMap = OpenMaya.MIntArray()

        #################################################
        # Collect necessary information for the splitUV #
        #                                               #
        # - uvSet                                       #
        # - faceIds / localVertIds per selected UV      #
        #################################################

        meshFn = OpenMaya.MFnMesh(self.__fMesh)
        selUVSet = meshFn.currentUVSetName()

        indexParam = OpenMaya.MScriptUtil(0)
        indexPtr = indexParam.asIntPtr()

        offset = 0
        selUVsCount = self.__fSelUVs.length()
        polyIter = OpenMaya.MItMeshPolygon(self.__fMesh)
        for i in range(selUVsCount):
            selUVFaceOffsetMap.append(offset)

            polyIter.reset()
            while not polyIter.isDone():
                if polyIter.hasUVs():
                    polyVertCount = polyIter.polygonVertexCount()

                    for j in range(polyVertCount):
                        polyIter.getUVIndex(j, indexPtr)
                        UVIndex = indexParam.getInt(indexPtr)

                        if UVIndex == self.__fSelUVs[i]:
                            selUVFaceIdMap.append(polyIter.index())
                            selUVLocalVertIdMap.append(j)
                            offset += 1
                            break

                polyIter.next()

        # Store total length of the faceId map in the last element of
        # the offset map so that there is a way to get the number of faces
        # sharing each of the selected UVs
        #
        selUVFaceOffsetMap.append(offset)

        ###############################
        # Begin the splitUV operation #
        ###############################

        currentUVCount = meshFn.numUVs(selUVSet)

        for i in range(selUVsCount):
            # Get the current FaceId map offset
            #
            offset = selUVFaceOffsetMap[i]

            # Get the U and V values of the current UV
            #
            uvId = self.__fSelUVs[i]

            uParam = OpenMaya.MScriptUtil(0.0)
            uPtr = uParam.asFloatPtr()
            vParam = OpenMaya.MScriptUtil(0.0)
            vPtr = vParam.asFloatPtr()
            meshFn.getUV(uvId, uPtr, vPtr, selUVSet)
            u = uParam.getFloat(uPtr)
            v = vParam.getFloat(vPtr)
            
            # Get the number of faces sharing the current UV
            #
            faceCount = selUVFaceOffsetMap[i + 1] - selUVFaceOffsetMap[i]

            # Arbitrarily choose that the last faceId in the list of faces
            # sharing this UV, will keep the original UV.
            #
            for j in range(faceCount-1):
                meshFn.setUV(currentUVCount, u, v, selUVSet)

                localVertId = selUVLocalVertIdMap[offset]
                faceId = selUVFaceIdMap[offset]

                meshFn.assignUV(faceId, localVertId, currentUVCount, selUVSet)

                currentUVCount += 1
                offset += 1


#####################################################################
## NODE #############################################################
#####################################################################

class splitUVNode(polyModifier.polyModifierNode):
    uvList = OpenMaya.MObject()


    def __init__(self):
        polyModifier.polyModifierNode.__init__(self)
        self.fSplitUVFactory = splitUVFty()


    def compute(self, plug, data):
        """
        Description:
            This method computes the value of the given output plug based
            on the values of the input attributes.
    
        Arguments:
            plug - the plug to compute
            data - object that provides access to the attributes for this node
        """
        stateData = 0
        state = OpenMayaMPx.cvar.MPxNode_state
        try:
            stateData = data.outputValue(state)
        except:
            statusError("ERROR getting state")

        # Check for the HasNoEffect/PassThrough flag on the node.
        #
        # (stateData is an enumeration standard in all depend nodes - stored as short)
        # 
        # (0 = Normal)
        # (1 = HasNoEffect/PassThrough)
        # (2 = Blocking)
        # ...
        #
        if stateData.asShort() == 1:
            try:
                inputData = data.inputValue(splitUVNode.inMesh)
            except:
                statusError("ERROR getting inMesh")

            try:
                outputData = data.outputValue(splitUVNode.outMesh)
            except:
                statusError("ERROR getting outMesh")

            # Simply redirect the inMesh to the outMesh for the PassThrough effect
            #
            outputData.setMObject(inputData.asMesh())
        else:
            # Check which output attribute we have been asked to 
            # compute. If this node doesn't know how to compute it, 
            # we must return MS::kUnknownParameter
            # 
            if plug == splitUVNode.outMesh:
                try:
                    inputData = data.inputValue(splitUVNode.inMesh)
                except:
                    statusError("ERROR getting inMesh")

                try:
                    outputData = data.outputValue(splitUVNode.outMesh)
                except:
                    statusError("ERROR getting outMesh") 

                # Now, we get the value of the uvList and use it to perform
                # the operation on this mesh
                #
                try:
                    inputUVs = data.inputValue(splitUVNode.uvList)
                except:
                    statusError("ERROR getting uvList")

                # Copy the inMesh to the outMesh, and now you can
                # perform operations in-place on the outMesh
                #
                outputData.setMObject(inputData.asMesh())
                mesh = outputData.asMesh()

                # Retrieve the UV list from the component list.
                #
                # Note, we use a component list to store the components
                # because it is more compact memory wise. (ie. comp[81:85]
                # is smaller than comp[81], comp[82],...,comp[85])
                #
                compList = inputUVs.data()
                compListFn = OpenMaya.MFnComponentListData(compList)

                uvIds = OpenMaya.MIntArray()
                for i in range(compListFn.length()):
                    comp = compListFn[i]
                    if comp.apiType() == OpenMaya.MFn.kMeshMapComponent:
                        uvComp = OpenMaya.MFnSingleIndexedComponent(comp)
                        for j in range(uvComp.elementCount()):
                            uvId = uvComp.element(j)
                            uvIds.append(uvId)

                # Set the mesh object and uvList on the factory
                #
                self.fSplitUVFactory.setMesh(mesh)
                self.fSplitUVFactory.setUVIds(uvIds)

                # Now, perform the splitUV
                #
                try:
                    self.fSplitUVFactory.doIt()
                except:
                    statusError("ERROR in splitUVFty.doIt()")

                # Mark the output mesh as clean
                #
                outputData.setClean()
            else:
                return OpenMaya.kUnknownParameter

        return None


#####################################################################
## REGISTRATION #####################################################
#####################################################################

def cmdCreator():
    return OpenMayaMPx.asMPxPtr(splitUV())


def nodeCreator():
    return OpenMayaMPx.asMPxPtr(splitUVNode())


def nodeInitializer():
    attrFn = OpenMaya.MFnTypedAttribute()

    splitUVNode.uvList = attrFn.create("inputComponents", "ics", OpenMaya.MFnComponentListData.kComponentList)
    attrFn.setStorable(True)    # To be stored during file-save

    splitUVNode.inMesh = attrFn.create("inMesh", "im", OpenMaya.MFnMeshData.kMesh)
    attrFn.setStorable(True)    # To be stored during file-save

    # Attribute is read-only because it is an output attribute
    #
    splitUVNode.outMesh = attrFn.create("outMesh", "om", OpenMaya.MFnMeshData.kMesh)
    attrFn.setStorable(False)
    attrFn.setWritable(False)

    # Add the attributes we have created to the node
    #
    splitUVNode.addAttribute(splitUVNode.uvList)
    splitUVNode.addAttribute(splitUVNode.inMesh)
    splitUVNode.addAttribute(splitUVNode.outMesh)

    # Set up a dependency between the input and the output.  This will cause
    # the output to be marked dirty when the input changes.  The output will
    # then be recomputed the next time the value of the output is requested.
    #
    splitUVNode.attributeAffects(splitUVNode.inMesh, splitUVNode.outMesh)
    splitUVNode.attributeAffects(splitUVNode.uvList, splitUVNode.outMesh)


def initializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject, "Autodesk", "1.0", "Any")
    try:
        mplugin.registerCommand(kPluginCmdName, cmdCreator)
    except:
        sys.stderr.write( "Failed to register command: %s\n" % kPluginCmdName)
        raise

    try:
        mplugin.registerNode(kPluginNodeTypeName, kPluginNodeId, nodeCreator, nodeInitializer)
    except:
        sys.stderr.write( "Failed to register node: %s" % kPluginNodeTypeName)
        raise


def uninitializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        mplugin.deregisterCommand(kPluginCmdName)
    except:
        sys.stderr.write("Failed to unregister command: %s\n" % kPluginCmdName)
        raise

    try:
        mplugin.deregisterNode(kPluginNodeId)
    except:
        sys.stderr.write("Failed to deregister node: %s" % kPluginNodeTypeName)
        raise