apiNode.py

import maya.api.OpenMaya as om
import sys


nodeName = 'myFirstNode'
nodeID = om.MTypeId(0x55555)
nodeClassify = 'utility/general'


def maya_useNewAPI():
    pass

  
class MyNode(om.MPxNode):
    inRadiusAttr = om.MObject()
    inTranslateAttr = om.MObject()
    outRotateAttr = om.MObject()

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

    # plug is MPlug type object, dataBlock is MDataBlock type object, refers to the entire datablock of the node
    def compute(self, plug, dataBlock):
        if plug == MyNode.outRotateAttr:
            # step one: get datablock handle (inputValue returns MDataHandle type object)
            inRadiusHandle = dataBlock.inputValue(MyNode.inRadiusAttr)
            inTranslateHandle = dataBlock.inputValue(MyNode.inTranslateAttr)
            outRotateHandle = dataBlock.outputValue(MyNode.outRotateAttr)

            # step two: extract input value from the handle
            inRadius = inRadiusHandle.asFloat()
            inTranslate = inTranslateHandle.asFloat()

            # step three: create logic and set output value
            outRotate = inTranslate/(6.18*inRadius) * -360
            outRotateHandle.setFloat(outRotate)

            # step four: mark output plug as clean
            outRotateHandle.setClean()

        # unknown plug, unknown error
        else:
            return om.kUnknownParameter

def nodeCreator():
    return MyNode()

def nodeInitializer():
    defaultRadius = 2.0
    defaultTranslate = 0.0

    # step one: create reference to attribute function set such as numericAttribute
    numericAttrFn = om.MFnNumericAttribute()

    # step two: create attribute using the function set
    MyNode.inRadiusAttr = numericAttrFn.create('radius', 'r', om.MFnNumericData.kFloat, defaultRadius)
    numericAttrFn.readable = True  # API1.0: numericAttrFn.setReadable(True)
    numericAttrFn.writable = True
    numericAttrFn.storable = True
    numericAttrFn.hidden = False
    numericAttrFn.keyable = True

    MyNode.inTranslateAttr = numericAttrFn.create('translate', 't', om.MFnNumericData.kFloat, defaultTranslate)
    numericAttrFn.readable = True
    numericAttrFn.writable = True
    numericAttrFn.storable = True
    numericAttrFn.hidden = False
    numericAttrFn.keyable = True

    MyNode.outRotateAttr = numericAttrFn.create('rotation', 'rot', om.MFnNumericData.kFloat)
    numericAttrFn.readable = True
    numericAttrFn.writable = False
    numericAttrFn.storable = False
    numericAttrFn.hidden = False

    # step three: attach attribute
    MyNode.addAttribute(MyNode.inRadiusAttr)
    MyNode.addAttribute(MyNode.inTranslateAttr)
    MyNode.addAttribute(MyNode.outRotateAttr)

    # step four: add circuit (relationship in->out)
    MyNode.attributeAffects(MyNode.inRadiusAttr, MyNode.outRotateAttr)
    MyNode.attributeAffects(MyNode.inTranslateAttr, MyNode.outRotateAttr)

def initializePlugin(mobject):
    mplugin = om.MFnPlugin(mobject)
    try:
        mplugin.registerNode(nodeName, nodeID, nodeCreator, nodeInitializer, om.MPxNode.kDependNode, nodeClassify)
    except:
        sys.stderr.write('fail to register node: ' + nodeName)
        raise

def uninitializePlugin(mobject):
    mplugin = om.MFnPlugin(mobject)
    try:
        mplugin.deregisterNode(nodeID)
    except:
        sys.stderr.write('fail to de-register node: ' + nodeName)
        raise