USD import losing normals when collapsing

Development Pipeline & Plugins
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Hi

We noticed an issue when an unsubdivided prim with authored normals is collapsed with a subdivision prim. The unsubdivision prim’s normals get recomputed/softened undesireably. I can reproduce this in launcher 5.7 and ue5-main from 2 weeks ago

Thank you

Luke

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Steps to Reproduce

Please see attached video

  1. Load the attached cubes.usd file into unreal using stage actor
  2. Disable any collapsing behaviour
  3. Set subdivision to 1
  4. Notice the cubes look as expected, 1 is flat shaded and unsubdivided, and the other is subdivided with smooth normals
  5. Collapse the 2 cubes into one static mesh
  6. Observe the Cube1, (which has subdivisionScheme set to “none”) now has got its normals recomputed because it has been merged with a subdiv prim
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Antony has been shown this issue and has responded.

"I ran this past Daniel, who implemented the collapsing feature, and this is a known issue right now unfortunately.

We need to spend time improving how collapsing is handled in these cases, making it smarter when encountering meshes utlilizing different subdivision schemes and different authored normals.

Let me know if this is a high priority request and we can see what we can do."

Brown Bag Films has been updated.

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