scripted/geomShader.py

#-
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########################################################################
# DESCRIPTION:
#
# Produces a dependency graph node "spGeomShader". 
#
# This node is an example of evaluating the geometric xyz position on an object.
#
# The inputs for this node are scale and offsets depicted as sliders in the
# Attribute Editor for the node.
#
# The output attribute of the spGeomShader node is called "outColor". It is a 3 float
# value that represents the xyz position on the object. To use this shader, create a
# spGeomShader node and connect its output "outColor" to an input of a surface/shader node
# like Color.
#
########################################################################

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

kPluginNodeName = "spGeomShader"
kPluginNodeClassify = "utility/color"
kPluginNodeId = OpenMaya.MTypeId(0x8700E)

class geomShader(OpenMayaMPx.MPxNode):
    def __init__(self):
        OpenMayaMPx.MPxNode.__init__(self)
        aOutColor = OpenMaya.MObject()
        aPoint = OpenMaya.MObject()
        aScale = OpenMaya.MObject()
        aOffset = OpenMaya.MObject()

    def compute(self, plug, block):
        if plug == geomShader.aOutColor or plug.parent() == geomShader.aOutColor:
            resultColor = OpenMaya.MFloatVector(0.0,0.0,0.0)
            
            point = block.inputValue( geomShader.aPoint ).asFloatVector()
            scale = block.inputValue( geomShader.aScale ).asFloatVector()
            offset = block.inputValue( geomShader.aOffset ).asFloatVector()

            resultColor.x = point.x * scale.x + offset.x
            resultColor.y = point.y * scale.y + offset.y
            resultColor.x = point.z * scale.z + offset.z

            outColorHandle = block.outputValue( geomShader.aOutColor )
            outColorHandle.setMFloatVector(resultColor)
            outColorHandle.setClean()
        else:
            return OpenMaya.kUnknownParameter


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

def nodeInitializer():
    nAttr = OpenMaya.MFnNumericAttribute()

    try:
        geomShader.aPoint = nAttr.createPoint("pointObj", "p")
        nAttr.setStorable(0)
        nAttr.setHidden(1)

        geomShader.aScale = nAttr.createPoint("scale", "s")
        nAttr.setKeyable(1) 
        nAttr.setStorable(1)
        nAttr.setReadable(1)
        nAttr.setWritable(1)
        nAttr.setDefault(1.0, 1.0, 1.0)

        geomShader.aOffset = nAttr.createPoint("offset", "o")
        nAttr.setKeyable(1) 
        nAttr.setStorable(1)
        nAttr.setReadable(1)
        nAttr.setWritable(1)

        geomShader.aOutColor = nAttr.createColor("outColor", "oc")
        nAttr.setStorable(0)
        nAttr.setHidden(0)
        nAttr.setReadable(1)
        nAttr.setWritable(0)

    except:
        sys.stderr.write("Failed to create attributes\n")
        raise

    try:
        geomShader.addAttribute(geomShader.aPoint)
        geomShader.addAttribute(geomShader.aScale)
        geomShader.addAttribute(geomShader.aOffset)
        geomShader.addAttribute(geomShader.aOutColor)
    except:
        sys.stderr.write("Failed to add attributes\n")
        raise

    try:
        geomShader.attributeAffects (geomShader.aPoint, geomShader.aOutColor)
        geomShader.attributeAffects (geomShader.aScale, geomShader.aOutColor)
        geomShader.attributeAffects (geomShader.aOffset, geomShader.aOutColor)
    except:
        sys.stderr.write("Failed in setting attributeAffects\n")
        raise


# initialize the script plug-in
def initializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        mplugin.registerNode( kPluginNodeName, kPluginNodeId, nodeCreator, 
                    nodeInitializer, OpenMayaMPx.MPxNode.kDependNode, kPluginNodeClassify )
    except:
        sys.stderr.write( "Failed to register node: %s" % kPluginNodeName )
        raise

# uninitialize the script plug-in
def uninitializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        mplugin.deregisterNode( kPluginNodeId )
    except:
        sys.stderr.write( "Failed to deregister node: %s" % kPluginNodeName )
        raise