Houdini 18 Solaris Add and Remove USD Rop node Output Processors with Python

hou18_solaris_python_addremove_usd_outputprocessors.py

import contextlib
import hou

def add_output_processor(ropnode, processor):
    """Add USD Output Processor to USD Rop node.

    Args:
        ropnode (hou.RopNode): The USD Rop node.
        processor (str): The output processor name. This is the basename of
            the python file that contains the Houdini USD Output Processor.

    """
    import loputils

    loputils.handleOutputProcessorAdd({
        "node": ropnode,
        "parm": ropnode.parm("outputprocessors"),
        "script_value": processor
    })


def remove_output_processor(ropnode, processor):
    """Removes USD Output Processor from USD Rop node.

    Args:
        ropnode (hou.RopNode): The USD Rop node.
        processor (str): The output processor name. This is the basename of
            the python file that contains the Houdini USD Output Processor.

    """
    import loputils

    parm = ropnode.parm(processor + "_remove")
    if not parm:
        raise RuntimeError("Output Processor %s does not "
                           "exist on %s" % (processor, ropnode.name()))

    loputils.handleOutputProcessorRemove({
        "node": ropnode,
        "parm": parm
    })


@contextlib.contextmanager
def outputprocessors(ropnode,
                     processors=tuple(),
                     disable_all_others=True):
    """Context manager to temporarily add Output Processors to USD ROP node.

    Args:
        ropnode (hou.RopNode): The USD Rop node.
        processors (tuple or list): The processors to add.
        disable_all_others (bool, Optional): Whether to disable all
            output processors currently on the ROP node that are not in the
            `processors` list passed to this function.

    """

    original_states = {}
    prefix = "enableoutputprocessor_"
    processor_parms = ropnode.globParms(prefix + "*")
    for parm in processor_parms:
        original_states[parm.name()] = parm.eval()

    if disable_all_others:
        for parm in processor_parms:
            parm.set(False)

    added = []
    for processor in processors:

        parm = ropnode.parm(prefix + processor)
        if parm:
            # If processor already exists, just enable it
            parm.set(True)

        else:
            # Else add the new processor
            add_output_processor(ropnode, processor)
            added.append(processor)

    try:
        yield
    finally:

        # Remove newly added processors
        for processor in added:
            remove_output_processor(ropnode, processor)

        # Revert to original values
        for parm_name, value in original_states.items():
            ropnode.parm(parm_name).set(value)

To quickly get all the created USD Rop Output Processors on the USD Rop node the trick is to do:

prefix = "enableoutputprocessor_"
processor_parms = ropnode.globParms(prefix + "*")

Then to get just their names we can strip of the beginning prefix:

prefix = "enableoutputprocessor_"
processor_parms = ropnode.globParms(prefix + "*")
processors = [parm.name()[len(prefix):] for parm in processor_parms]

Reload all Houdini USD Output Processor Python modules for easier development.

import hou
import importlib

def reload_all_processors():
    """Quick utility to reload all Houdini USD ROP Output Processors modules"""
    # Force reload on all Houdini USD Output Processors
    for name, description in hou.lop.outputProcessors():
        module = importlib.import_module("husdoutputprocessors.%s" % name)
        print("Reloading %s" % module)
        reload(module)

reload_all_processors()