Importing meshes with time-sampled, yet constant topology

[pierre-ed]

Hello and apologies if this is a duplicate (I did browse existing discussions 🙂 ).

We attempted to import a basic animated UsdGeomMesh
which resulted in an empty Maya polymesh.
Upon closer inspection, we realized it may be due to its topology (faceVertexCounts and faceVertexIndices) which, while effectively constant, exhibits time samples.

Is there any way around this, besides altering the USD data ?
Could this limitation be lifted in the future ?

Attached to this discussion are two descriptions of the same quick animation:

• anim-homogeneous_topology.usda (constant topology)
• anim-heterogeneous_topology.usda (time-sampled, yet unchanging topology)

By running the following script:

from maya import cmds


def import_file(filename):
    root = cmds.mayaUSDImport(file=os.path.join(dirpath, filename), readAnimData=True)
    shape_path_segments = [
        root[0],
        "geo",
        "fx_oilLampA_fireGeo_geo",
        "fx_oilLampA_fireGeo_geoShape",
    ]
    shape_path = "|".join(shape_path_segments)
    msg = "imported {}\n\tshape exists? {}\n\tshape vertices: {}\n".format(
        filename,
        cmds.objExists(shape_path),
        cmds.ls(".".join((shape_path, "vtx[*]"))),
    )
    print(msg)


import_file("anim-homogenous_topo.usda")
import_file("anim-heterogenous_topo.usda")

we get the following results which indicates that only the mesh with a constant, single-valued topology is imported into a complete Maya shape:

imported anim-homogenous_topo.usda
 shape exists? True
 shape vertices: [u'world10|geo|fx_oilLampA_fireGeo_geo.vtx[0:449]']

# Error: line 1: Connection not made: 'fx_oilLampA_fireGeo_geoShape.instObjGroups[0]' -> 'set1.dagSetMembers[-1]'.  Destination node will not allow the connection. # 
# Error: line 1: Connection not made: 'fx_oilLampA_fireGeo_geoShape.instObjGroups[0]' -> 'set2.dagSetMembers[-1]'.  Destination node will not allow the connection. # 
imported anim-heterogenous_topo.usda
 shape exists? True
 shape vertices: []

Specs

• OS & version: CentOS Linux release 7.6.1810 (Core)
• Compiler & version: gcc (GCC) 6.3.1 20170216
• Maya version: Maya 2022.3-981
• Maya USD: 0.23.0
• Pixar USD: 21.11