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USD - Shading group not imported

Unread postPosted: Sat Apr 04, 2020 1:41 pm
by machieb

is there a reason why shading groups get not imported with an USD-file. I reported this once as a bug (#10390) and it was set to resolved.
It is under the things that got resolved in SP6:
"Fixed shading group loading in USD references and bundles. Loading UV maps is also more robust as it now checks for the TextureCoordinate USD role name in attributes. (#10390)"
I waited for SP6 but the problem still persists. The shading group is always on default when importing a USD-file. With alembic it works but not with USD. If I import the reference USD-files from pixar they also have only the default shading group on them. The only thing that is different from before SP6 is that now there are different viewport colors on different geometries (see attachment).
When I export a mesh from blender also the shading group is not transfered to clarisse. Only If I assign shading groups per polygon (see attachment).

Is there a reason for this? Aren't there shading groups on the USD-reference files from pixar? Is USD handling shading groups different?
Should I reopen the above mentioned ticket?

Thanks Marcus

Re: USD - Shading group not imported

Unread postPosted: Mon Apr 06, 2020 8:39 am
by dboude
I don't know in Blender but in Maya when you assign a material on the object you will have a shading group named default, but if you assign the material to the primitives it works fine. We do not read shading group assigned to object, but to primitives only and I don't know if it is even possible.


Re: USD - Shading group not imported

Unread postPosted: Mon Apr 06, 2020 10:41 am
by dcourtois

KitchenSet (the ref from Pixar) has no shading groups. Please check the assets in UsdView, you'll see by yourself.
Also, I don't know the specifics of Blender, but from the first screenshot, it seems that shading groups are there, right ? So if I'm understanding things correctly: there are 2 different ways to assign shading groups in Blender, one of them works (the screenshot you posted) and the other not ?

And in any case, for the version that you say doesn't work: did you try to import this USD in another package to see if the USD file itself has valid shading groups ?