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StandardShaderBall: Polygon winding order #70

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msuzuki-nvidia opened this issue Dec 14, 2023 · 5 comments
Open

StandardShaderBall: Polygon winding order #70

msuzuki-nvidia opened this issue Dec 14, 2023 · 5 comments

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@msuzuki-nvidia
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Currently the polygon winding order in the USD file is left-handed, which is Houdini's default. While this is compliant with the USD spec, switching to right-handed orientation might cause fewer issues for other DCC tools that assume a right-handed mesh.

SOP Import node has an option Reverse Polygon Vertex Ordering to change the winding order.
@crydalch
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Hi @msuzuki-nvidia! Thanks for the suggestion. I'm curious, which DCC's have you found struggling with left-handed meshes? As you mentioned, meshes can be either right- or left-handed in USD, so it's surprising this would be a problem for a tool with USD support (especially at this point, now that USD's been out for a while).

@crydalch
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Added #74 to track a separate test asset, that exemplifies both mesh types (as well as other important properties of the mesh schema).

@msuzuki-nvidia
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Hi @crydalch, initially I encountered an issue in Omniverse (it is reported internally and going to be fixed), but also found that Maya interprets the UVs incorrectly if I read the USD file via "File > Import".

maya_import

Interestingly, the same USD file works fine if it's referenced via "Create > USD > Stage From File".

maya_usd_reference

I understand that these are application specific issues, but making less trouble could improve the user experience.

crydalch added a commit to crydalch/assets that referenced this issue Feb 23, 2024
@crydalch
Changed mesh orientations, added normals to triangle mesh, clarified …
07e13a3 
…camera.

To make it easier for tools which don't yet read both types of USD meshes, this commit changes the geometry to be rightHanded. There should be no visual differences for renderers/software that recognize meshes could have either winding order. (Issue usd-wg#70)

The triangulated variant now has `normals` authored as well now (Issue usd-wg#69)

Also re-authored the Camera transform using XformCommonAPI, rather than a 4x4 Matrix, so the translate/rotate values are clear.
@crydalch crydalch mentioned this issue Feb 23, 2024
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@crydalch
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@msuzuki-nvidia can you log an issue on the Maya-USD repo, about recognizing mesh winding order and texture coordinates? PR #80 will change the repo, so adding a repro case to the ticket will probably be helpful.

@msuzuki-nvidia
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@crydalch submitted an issue there

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@crydalch @msuzuki-nvidia