"Generate Lightmap UVs" breaks Shapekeys

[ludwigseibt]

Describe the bug 💬

When you enable "Generate Lightmap UVs" shapekeys brake and seemingly affect random vertices instead of the ones they are supposed to. Some sort of index mismatch I expect.
I am using Unity 6000.3.6f1 LTS

Steps to reproduce 🔢

• Create Object with Shapekey in Blender
• Export
• Generate Lightmap UVs
• Its broken

Files to reproduce the issue ♻

No response

Editor Version 🎲

Other (Provide details below)

Render Pipeline and version

URP 17.3.0

UnityGLTF Version

2.18.9

Operating System 👩‍💻

Linux

When does this problem happen?

• Editor Import
• Runtime Import
• Editor Export
• Runtime Export

Additional Info 📜

Unity 6000.3.6f1 LTS

Validations 🩹

• I have searched existing issues: no issue already exist that reports the same problem.
• I follow the Code of Conduct
• I provided a minimal reproducible example, including files when necessary.

[robertdorn83]

Hey,
Generate Lightmaps come from a Unity function with some limitation..
But, in cases where this function needs to split vertices for proper UV creation, the indices will not stay the same. So in case you need Lightmaps UVs, they way to solve this is just create a second UV set in blender.

i will keep this open for now, unitl i added a warning or something like that for these import issues.
but there is no action we could fix this properly for such cases.

[hybridherbst]

Hey @ludwigseibt can you please include a minimal reproducible example? You checked that checkbox but I don't see a file attached.

[ludwigseibt]

unitygltf-shapekeys.zip
Extract zip. Import glb into Unity. Observe shapekey. Enable Generate Lightmap UVs. Observe broken shapekey.

[robertdorn83]

hey,
have added support for this case with 678863a.
Will be available with the next release soon.
Would be good if you can test it then and give feedback.
Until then i will let this open for now :)

[ludwigseibt]

I tested 2.21.0 and it works. Thanks! Can be closed.