[MAYA-127103] Importer Errors when importing animated meshes that are skinned

[dgovil]

Describe the bug
If you import a USD file that has a mesh that is both skinned and vertex animated, the importer will error with:

# Error: Connection not made: 'skinCluster_pCylinder2.outputGeometry[0]' -> 'pCylinder1Shape.inMesh'. Destination attribute must be writable.

Unfortunately, this is an issue when a Mesh has even just a single static time sample as in the example below

NOTE: This error only shows up if you import using the mayaUSDImport command. If you use the file import command, it will not show up for some reason. Not sure if it's just swallowing the error or if it's somehow taking a different path.

I think both vertex animation and skinning should be able to coexist. However the issue is that the Maya USD importer imports vertex animation as blendshapes which then takes up the inMesh connection. Perhaps if it's skinned, it should add another blendshape for the skinning to apply to, and then have the blendshapes combine into the final inMesh?

Steps to reproduce
Steps to reproduce the behavior:

1. Import the file with readAnimData set to True

cmds.mayaUSDImport(f="/Users/dhruvgovil/Documents/maya/projects/default/scenes/foo.usda", readAnimData=True)

Expected behavior
I'm honestly not sure what the right behaviour here should be:

• Warn the user and take just the skinning (ignoring the vertex animation)
• Error when it detects both with a clear error?
• Try and import both?
• At the very least I think the vertex animation importer should detect when something is a single keyframe, and treat it as static if it can.

Attachments
foo.usda.zip

Specs (if applicable):

• OS & version : macOS 13
• Compiler & version : clang 14
• Maya version 2023.2
• Maya USD commit SHA 8b7b598
• Pixar USD commit SHA release at 0c7b9a95f155c221ff7df9270a39a52e3b23af8b

[neilh-adsk]

I ran into a few other smaller inconsistencies with vertex animation and skinning locally. I didn't manage to isolate those problems, but just to say it an area that is growing in attention. I'll bring this into the backlog and track it with any other issues we are seeing.

[santosd]

@neilh-adsk should we log an issue for this internally?

[neilh-adsk]

@santosd Yes, please log this and I'll flag it followup

[santosd]

Logged this internally as MAYA-127103

[santosd]

Hi @dgovil, we currently don't have this in the scope for an upcoming release. I wanted to get a sense from you what first of all the impact is for your team with this one and second if this is something that you would like to submit a pull request for to fix.

[dgovil]

Good to know. This isn't high impact for us so we haven't put together a fix yet.

If it does become more of an issue, I'll have us put up whatever fix we come up with at that point.

[maya-usd-git-sync]

Issue synced internally to EMSUSD-740

[barbalt]

Closing this issue as it has been addressed by #2860