openMaya api nodes

Coding
#1

anyone got examples of working with nodes using the API from python, just simple stuff like creating a polyExtrudeEdge node and hooking it up to a mesh.

#2

This autodesk example gives you the basics.

Unless you’re doing this in a plugin where you need to use API code – or doing something that’s super perf critical – it’s rarely worth the hassle of doing this in the API when the cmds/pymel route is viable. API code is a lot more work for the same results most of the time.

#3

it’s needed from the API, since it would be executed from a custom context i am making, on it’s doRelease method.

Though im still trying to weigh the benefits of using the node or just modifying the mesh via MfnMesh since i will be using this in a retopo type tool.

Thanks for the link.

#4

little off topic, but i need to figure this out for the same tool, what is the best method for getting vertex ids, from a dag path and component mobject returned from a selection list? Sofar all i can think of is using a MItMeshVert and it’s index() method, though that dosnt seem very efficient, i need this so i can work with the data in a MfnMesh function set.

edit:
MFnSingleIndexedComponent seems to be the best way i found sofar

#5

Can’t you use maya.cmds in a custom context? Why do you need to connect an extrude using the API and not by calling polyExtrude?

#6

Can’t really help with what you need, but here is some api code for creating a node.

Here is a simple math node I created a while back. It’s handy just to use as a template.



import sys
import maya.OpenMaya as OpenMaya
import maya.OpenMayaMPx as OpenMayaMPx
##set vars
kAddUtilNodeTypeName = "Add"
kAddUtilNodeClassify = "utility/general"
kAddUtilNodeId = OpenMaya.MTypeId(0x87327)

# define a new matrixUtilNode class derived from the MPxNode class
class rtAddUtilNode(OpenMayaMPx.MPxNode):

	# class variables
	input = OpenMaya.MObject()
	input1 = OpenMaya.MObject()
	input2 = OpenMaya.MObject()
	output = OpenMaya.MObject()

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

	# arguments ( self, MPlug, MDataBlock)
	def compute(self, plug, dataBlock):

		# if these attributes are requested, recompute their values
		if  plug == rtAddUtilNode.output:

			# get MDataHandle's to attributes
			#
			try:
                            input_dataHandle1 = dataBlock.inputValue( rtAddUtilNode.input1 )
			except:
			    sys.stderr.write( "Failed to get MDataHandle inputValue input1" )
			    raise
                        try:
                            input_dataHandle2 = dataBlock.inputValue( rtAddUtilNode.input2 )
			except:
			    sys.stderr.write( "Failed to get MDataHandle inputValue input2" )
			    raise
			
			try:
			    output_dataHandle = dataBlock.outputValue( rtAddUtilNode.output )
			except:
			    sys.stderr.write( "Failed to get MDataHandle outputValue output" )
			    raise

			# get values from dataHandle
			#
			input_value1 = input_dataHandle1.asFloat()
                        input_value2 = input_dataHandle2.asFloat()
                        result = input_value1 + input_value2
			# set the output
			output_dataHandle.setFloat(result)

			# set the plug clean so maya knows it can update
			dataBlock.setClean(plug)

		else:
			return OpenMaya.kUnknownParameter

		return OpenMaya.MStatus.kSuccess

def nodeCreator():

	return OpenMayaMPx.asMPxPtr( rtAddUtilNode() )

# create and initialize the attributes to the node
def nodeInitializer():

	nAttr = OpenMaya.MFnNumericAttribute()

	# create input attributes
	#
	rtAddUtilNode.input1 = nAttr.create("input1", "i1", OpenMaya.MFnNumericData.kFloat, 0.0)
	nAttr.setWritable(True)
	nAttr.setStorable(True)
	nAttr.setReadable(True)
	nAttr.setKeyable(True)
	
	rtAddUtilNode.input2 = nAttr.create("input2", "i2", OpenMaya.MFnNumericData.kFloat, 0.0)
	nAttr.setWritable(True)
	nAttr.setStorable(True)
	nAttr.setReadable(True)
	nAttr.setKeyable(True)


	rtAddUtilNode.output = nAttr.create("output", "o", OpenMaya.MFnNumericData.kFloat, 0.0)
	nAttr.setWritable(True)
	nAttr.setStorable(True)
	nAttr.setReadable(True)
	
	# add attribues
	#
	rtAddUtilNode.addAttribute( rtAddUtilNode.input1)
	rtAddUtilNode.addAttribute( rtAddUtilNode.input2)
	rtAddUtilNode.addAttribute( rtAddUtilNode.output)

	# Setup which attributes affect each other
	rtAddUtilNode.attributeAffects ( rtAddUtilNode.input1, rtAddUtilNode.output )
        rtAddUtilNode.attributeAffects ( rtAddUtilNode.input2, rtAddUtilNode.output )
# initialize the script plug-in
def initializePlugin(mobject):
	mplugin = OpenMayaMPx.MFnPlugin(mobject, "Tim Callaway", "1.0", "Any")
	try:
		mplugin.registerNode( kAddUtilNodeTypeName, kAddUtilNodeId, nodeCreator, nodeInitializer, OpenMayaMPx.MPxNode.kDependNode, kAddUtilNodeClassify)
	except:
		sys.stderr.write( "Failed to register node: %s" % kAddUtilNodeTypeName )
		raise

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