A Maya to Arnold (MtoA) extension to allow export of new node types using python scripts.

• Arnold 4.1 or above
• Maya 2013 or above
• MtoA 1.0.0.1 or above

  scons with-mtoa=<path_to_mtoa_install_dir>
        with-arnold=<path_to_arnold_install_dir>
        with-maya=<path_to_maya_install_dir>

If maya is installed in its default system location, the 'maya-ver=target_maya_version' can be used instead of 'with-maya=...'

Add the build output folder to your MAYA_EXTENSIONS_PATH

When the extension is loaded by MtoA, it will look at the contents of the MTOA_SCRIPTED_TRANSLATORS environment variable.

It expects a colon or semicolon separated list of 'node_type,plugin_name' items. If the plugin name matches the node type, it can be omitted.

For each found node type, the extension will try to import a python module named 'mtoa_node_type'. When it succeeds doing so, it will then look up for a function named 'Export' in the module. Only then will the node type be registered to MtoA.

Other functions may be defined to control the behavior of the extension, but only the 'Export' one is required. Follows a full list of recognized functions with their arguments and expected return values:

• IsShape()

Returns whether or not the translator should be based on CNodeTranslator or CShapeTranslator MtoA class.

When not defined, it will be considered True.

• SupportVolumes()

Returns whether or not the generated arnold procedural handles volume shapes. If not, extension will generate a box node rather than a procedural if maya's node has a aiStepSize attribute with its value set above 0.

When not defined, it will be considered False.

• SupportInstances()

Returns whether or not a ginstance node should be generated rather that a procedural node if the maya node is an instance.

When not defined, it will be considered False.

• Export(renderFrame, mbStep, mbSampleFrame, nodeNamePair, masterNodeNamePair)

parameter nodeNamePair: tuple (mayaNodeName, arnoldNodeName)

parameter masterNodeNamePair: None or tuple (mayaNodeName, arnoldNodeName)

Returns a list of attributes that have been explicitly set in the function. All attributes appearing in this list won't be handled by the extension.

• Cleanup(nodeNamePair, masterNodeNamePair)

parameter nodeNamePair: tuple (mayaNodeName, arnoldNodeName)

parameter masterNodeNamePair: None or tuple (mayaNodeName, arnoldNodeName)

Called on last export step to cleanup any internally maintained data.

• SetupAttrs()

Returns a list of string describing the attributes that are to be added to every node of that type (use scriptedTranslatorUtils.AttrData).

def SetupAttrs():
    import scriptedTranslatorUtils as stu
    import arnold
　　　
    attrs = []
    　　　
    # Add step_size parameter from arnold box node
    attrs.append(stu.AttrData(arnoldNode="box", arnoldAttr="step_size"))
    　
    attrs.append(stu.AttrData(name="aStringAttribute",
            shortName="asa", 
            type=arnold.AI_TYPE_STRING,
            defaultValue=""))
    
    attrs.append(stu.AttrData(name="aFloatAttribute",
            shortName="afa", 
            type=arnold.AI_TYPE_FLOAT,
            defaultValue=0.0,
            softMin=0.0,
            softMax=1.0,
            max=10.0))
    
    attrs.append(stu.AttrData(name="anEnumAttribute",
            shortName="aea",
            type=arnold.AI_TYPE_ENUM,
            enums=["aaa", "bbb", "ccc"],
            defaultValue=1))
    
    return map(str, attrs)

• SetupAE(translatorName)

Attribute editor setup.

def SetupAE(translatorName):
    import mtoa.ui.ae.templates as templates
    
    class MyNodeTtemplate(templates.ShapeTranslatorTemplate):
        def setup(self):
            # Setup attributes automatically added by MtoA
            self.commonShapeAttributes()
            self.addSeparator()
            self.renderStatsAttributes()
            self.addSeparator()
            self.addControl("aiUserOptions", label="User Options")
            self.addSeparator()
            
            # Setup myNode specific attributes
            self.addControl("aiStepSize", label="Volume Step Size")
            self.addControl("aStringAttribute")
            self.addControl("aFloatAttribute")
            self.addControl("anEnumAttribute")
    
    templates.registerTranslatorUI(MyNodeTtemplate, "myNode", translatorName)

The extension will take care of creating the arnold nodes depending on IsShape, SupportVolumes and SupportInstances function return value.

Only procedural are generated if IsShape is defined and returns False. For shape nodes, if the node aiStepSize attribute is defined and its value is greater than 0, a box node is generated for the master node instance and ginstance node for all secondary instances when SupportVolumes is not defined or returns False. In any other case, a procedural node is always generated for the master instance. For secondary instances, a ginstance is generated if SupportInstances function is defined and returns True; a procedural node otherwise.

For shape nodes, the extension will recognize and export standard shape attributes (visibility, mesh subdivision, trace sets, sss, etc...), user attributes, transform, bounding box and object level assigned surface/displacement shaders.

When a parameter doesn't exist on the generated arnold node, it will be added as a user attribute. It is then up to the procedural to pass it on to the nodes it generates. disp_padding is also automatically taken into account when generating procedural bounds.