Exporting mayaUsdProxyShape node doesnt keep edits

[sbissonnette]

Describe the bug
When we try to export a mayaUsdProxyShape as a Maya scene, it doesn't export the USD edits that was living in the Maya scene. This means any composition/edit made from that Stage node is not being exported (Anonymous layers, EditTarget, PrimSpec/AttrSpec, new defs, etc).

Steps to reproduce
At its simplest way to reproduce the issue:

1. Create Stage with New Layer
2. Create a sphere Prim
3. Select mayaUsdProxyShape node
4. File -> Export Selection -> .ma

Expected behavior
Any USD Data that would normally be saved within the Maya scene should also be exported (Anonymous layers, EditTarget's Prim/AttrSpec, etc). The Export should act exactly like the "Save all edits (including USD) to the Maya scene file".

Specs:

• Alma Linux 9.4
• Maya 2024
• mayaUsd 0.30 & 0.31

Additional Info:

• Our Save USD Options is set to "Save all edits (including USD) to the Maya scene file"

[wallworm]

When exporting a Maya scene to USD, you will only see the results of a USD Stage in the scene if you are using a stage that references a file on disc. Our exporter will generate an XForm with a Reference to that file. If the stage has an anonymous root, the stage is skipped and will not be referenced. This is by design.

To get the results you expect, you will need to save your stage to a file on disk. That file can then be referenced in other scenes. Even in this case, edits to the session layer or edits contained only in the Maya scene will be missing from other scenes referencing the root layer.

[sbissonnette]

If the stage has an anonymous root, the stage is skipped and will not be referenced. This is by design.

This raise another issue: If your Root Layer is from a file, working with session layers becomes destructive. In fact, if you made some changes in the SessionLayer and try to update the RootLayer, all your work will be lost.

Here is an Example:

What we do instead: Our Root Layer is always anonymous and we sublayer files beneath it. This way it's more flexible to update Sublayer paths, and any work done from the SessionLayer won't be lost.

[sbissonnette]

In any case, I personally don't see any difference between saving a scene with USD Edits or exporting a maya scene with USD Edits as well.

[sbissonnette]

For more context, we want to be able to export Maya Scenes with USD Edits because we are splitting a Sequence Scene into Individual Shots. So we have tools using the Camera Sequencer that analyse what's visible from Camera Frustrum and export Maya Scenes from that.

So we want to export individual scenes that matches the exact same state from Source Scene. Thus exporting mayaUsdProxyShape with its edits. For us at this time it doesnt make sense to save this stage & edits on disk. We would want the same exact behavior from the "Save all edits (including USD) to the Maya scene file", but for the " File -> Export Selection" button

[wallworm]

Thank you for the input. We have considered the effort of taking on edits into scene exports when we added support to export a proxyshape as a reference, so this is validation that at least some users will want that. We will consider it for a future update.

[sbissonnette]

As of now to answer our needs, we can workaround by cleaning up our "Sequence scene" for each Individual shots and use the "Save all edits (including USD) to the Maya scene file" from Save Scene feature. This is a bit more work but feasible.

Looking forward to export proxyShape with Edits!