Export Pointcache: Optimize forced shader assignments when writing face sets

[BigRoy]

Changelog Description

Export Pointcache: Optimize forced shader assignments when writing face sets

Additional review information

Fix #441

To performance test:

import datetime

from ayon_maya.api.lib import force_shader_assignments_to_faces
from maya import cmds


##############################################

prev_time = datetime.datetime.now()

def log(*args, reset=False):
    global prev_time
    if reset:
        prev_time = datetime.datetime.now()

    now = datetime.datetime.now()

    ts = now.strftime("%H:%M:%S")
    diff = now - prev_time
    diff_s = diff.total_seconds() % 60
    diff_m = diff.total_seconds() // 60
    diff_str = f"{diff_m:.0f}m {diff_s:5.2f}s"
    print(f"[{ts} +{diff_str}]", *args)
    prev_time = now


##############################################

def add_cubes(count=100):
    root = cmds.group(empty=True, name="root")
    for i in range(count):
        transform, _ = cmds.polyCube(name=f"cube{i:02d}")
        cmds.parent(transform, root)


def main():
    cmds.file(newFile=True, force=True)
    log("start", reset=True)

    log("add cubes")
    add_cubes(5_000)
    log("cubes added")

    meshes = cmds.ls("cube*", type="mesh", long=True)
    log("found", len(meshes), "cubes")

    log("pre enter")
    with force_shader_assignments_to_faces(meshes):
        log("in")
        pass
    log("out")


if __name__ == "__main__":
    main()

Testing notes:

1. Publishing with write face sets should still work and produce correct results.
2. It should be faster.

[Copilot]

Pull request overview

This PR targets the performance bottleneck in force_shader_assignments_to_faces used during pointcache export (write face sets), by replacing slow cmds.sets(clear=...) / cmds.sets(..., forceElement=...) operations with Maya API 2.0 (OpenMaya) set membership operations and a custom “fast clear” implementation.

Changes:

• Added _get_mobject and _fast_clear_set helpers to work with sets via OpenMaya and clear set membership by disconnecting dagSetMembers.
• Reworked force_shader_assignments_to_faces to gather/apply/revert set members using OpenMaya.MFnSet.getMembers / addMembers and MSelectionList instead of cmds.sets member lists.

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[moonyuet]

Tested successfully in Maya 2027

[LiborBatek]

I couldnt achieve an alembic containing any face sets no matter how hard I have tried...I also tried not just pointcache but also model in alembic repre but no luck...

interestingly even if I deviated from the default values for Write Face Sets which were Disabled by default...it start to validate only if publishing the pointcache but not when trying to produce a model and Alembic repre...which brings me feeling that while trying to use it for model it still sticks to the defaults (AYON didnt fail on validation when overriding those defaults - or these arent triggered and gracefully ignored) As I was inspecting my published pointcache and model I havent found any face sets whatsoever...

Here is my hierachy and graph before and after loading resulting product: