Support AYON dirmap

[BigRoy]

Is there an existing issue for this?

• I have searched the existing issues and added correct labels.

Please describe the feature you have in mind and explain what the current shortcomings are?

AYON core offers functionality to expose 'dirmapping' across host integrations, e.g. in Maya and Nuke.

Houdini has some functionalities for that as well, called path mapping. E.g. see HOUDINI_PATHMAP env var or the pathmap command.

The Deadline docs also mention using Houdini's Path mapping.

Suggested implementation?

Apply the relevant dirmapping using HOUDINI_PATHMAP or the pathmap hscript function.

Describe alternatives you've considered:

There have been reports that in some cases the Houdini dirmap will fail to do what it intends to do, e.g. for a plug-in like Arnold.
More extreme fallback methods are instead calling e.g. hscript's opchange to change string values across all string parms in the scene.

# pseudocode
def pathmap():
    '''
    Fix possible Linux/Windows paths
    '''
    source = {windows}
    destination = {linux}

    if platform.system() in ("Windows", "Microsoft"):
        hou.hscript("opchange {0} {1}".format(destination, source))
    else:
        hou.hscript("opchange {0} {1}".format(source, destination)

Side-note: Using opchange for this instead of going through hou.fileReferences makes a huge speed difference and avoids long cooking times during the operation in e.g. heavy vellum sim scenes.

Here's some more discussion on potential pitfalls using Houdini path mapping.