camera custom node (maya plugin)

camNode.py

##@file camNode.py  
#
#Track start and end frames and a transform in Maya(Tested Maya 2008)
#
#@author Nathaniel Anozie
#
#
#@note Inspired by Maya's api tutorials and examples on sineNode.py and lambertShader.cpp
#
##

#for some error checking
import sys

#get necessary api functions
import maya.OpenMaya as OpenMaya

#need this because were making a node
import maya.OpenMayaMPx as OpenMayaMPx

kPluginNodeTypeName = "camNode"
#using a temporary id
camNodeId = OpenMaya.MTypeId(0x0000)


#build our node off of Maya's our constructor needs to call parent class
class camNode(OpenMayaMPx.MPxNode):
    
    #in c these are protected, they are the attribute names
    transform = OpenMaya.MObject()
    startFrame = OpenMaya.MObject()
    endFrame = OpenMaya.MObject()
    
    output = OpenMaya.MObject()
    
    def __init__(self):
        OpenMayaMPx.MPxNode.__init__(self)
        
    ##use inputs of node to generate output
    #@note in c explicitly give it the type for input parameters, in python types are ommited
    #@param plug tells us the attributes that need to be recomputed
    #@param use dataBlock to find all nodes attributes can use
    ##    
    
    def compute(self,plug,dataBlock):
        
        #in c would have ommited the class part
        if( plug == camNode.startFrame ):
            print 'Great An Update in -- startFrame'
            #in c what is returned from block.inputValue(...) is a reference ex a MFloatVector&
            #in python forgetting about the type that is returned
            sframeHandle = dataBlock.inputValue(camNode.startFrame)
            startFloat = frameHandle.asFloat()
            print 'Start Frame is >>%d' %startFloat
            #mark plug as clean
            dataBlock.setClean(plug)
            
        if( plug == camNode.endFrame ):
            print 'Great An Update in -- endFrame'
            eframeHandle = dataBlock.inputValue(camNode.endFrame)
            endFloat = eframeHandle.asFloat()
            print 'End Frame is >>%d' %endFloat
            dataBlock.setClean(plug)

        if( plug == camNode.transform ):
            print 'Great An Update in -- transform'
            tfHandle = dataBlock.inputValue(camNode.transform)
            tfFloat = tfHandle.asFloat()
            print 'Transform is >>%d' %tfFloat
            dataBlock.setClean(plug)
            
        if( plug == camNode.output ):
            print 'Great an Update in Ouput'
            #in c would have passed output and maybe an error checking object
            outHandle = dataBlock.outputValue( camNode.output )
            #mark output value as clean
            #in c i think would have used the handle to setClean not the dataBlock
            dataBlock.setClean(plug)
     

            
##allow Maya to instantiate an instance of our custom node, its called every time a new instance
#of node is made ex: with Maya's createNode command
#@note in c this is creator()
##
def nodeCreator():
    return OpenMayaMPx.asMPxPtr( camNode() )

    
##create the node attributes and set their types, keyable status ets
#this is called once when Maya loads the plugin ex: pressing load in plugin manager
#@note in c this is initialize()
##
def nodeInitializer():
    #"""
    #similar in c, this is needed to create numeric attributes for our node
    
    #startFrame
    nAttr = OpenMaya.MFnNumericAttribute();
    #This part actually creates the attribute, in c the create would also take a status object
    #also in c would have set default value separately using setDefault(...)
    camNode.startFrame = nAttr.create( "startFrame","sf", OpenMaya.MFnNumericData.kFloat, 0.0)
    #so when file is saved the attribute is written out
    nAttr.setStorable(1)
    #so setAttr commands can change this attribute, and attribute can be a connection destination
    nAttr.setWritable(1)
    #so cannot be keyframed
    nAttr.setKeyable(0)
    
    #endFrame
    nAttr = OpenMaya.MFnNumericAttribute();
    camNode.endFrame = nAttr.create( "endFrame","ef", OpenMaya.MFnNumericData.kFloat, 0.0)
    nAttr.setStorable(1)    
    nAttr.setWritable(1)
    nAttr.setKeyable(0)
    
    #transform
    nAttr = OpenMaya.MFnNumericAttribute();
    camNode.transform = nAttr.create( "camTransform","ct", OpenMaya.MFnNumericData.kFloat, 0.0)
    nAttr.setStorable(1)    
    nAttr.setWritable(1)
    nAttr.setKeyable(0)
    
    #output
    nAttr = OpenMaya.MFnNumericAttribute();
    camNode.output = nAttr.create( "output","out", OpenMaya.MFnNumericData.kFloat, 0.0)
    nAttr.setStorable(1)  
    nAttr.setWritable(1)
    nAttr.setKeyable(0)
    
    
    #now we add the attributes to the node
    camNode.addAttribute(camNode.startFrame)
    camNode.addAttribute(camNode.endFrame)
    camNode.addAttribute(camNode.transform)
    camNode.addAttribute(camNode.output)
    
  
##so when plug in loaded Maya can register the node
#
##
def initializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        mplugin.registerNode( kPluginNodeTypeName, camNodeId, nodeCreator, nodeInitializer)
    except:
        sys.stderr.write("Failed register node: %s" %kPluginNodeTypeName)
        raise
        
def uninitializePlugin(mobject):
    mplugin = OpenMayaMPx.MFnPlugin(mobject)
    try:
        #only need the id to deregister node
        mplugin.deregisterNode(camNodeId)
    except:
        sys.stderr.write("Failed deregister node: %s" %kPluginNodeTypeName)
        raise