How do I export shading groups in USD files?

[mrakgr]

I have a scene done entirely in the obj context for which I want to assign shading groups so that I can export it from Houdini and import it in Clarisse as USD and do the lookdev there. When exporting .obj files, just having the shop_materialpath attribute is enough to delineate the shading groups, but that does not work when exporting USD scenes. What should I do to make this work?

[dleonhardt]

You need to import your geometry into the Stage context, apply the materials and export from the Stage context. The SOP Level USD Export doesn't know what to do with 'shop_materialpath'.

[mrakgr]

I see now that I can use primitive groups to set shading groups in USD. To make this work, I have to mark them as Subset Groups in Import Data in the USD Export nodes either LOP or SOP.

I've also figured out that putting in * works for exporting groups even in packed and nested packed primitives, but that would be too much. Instead I should be able to prefix the groups and then put in something like s_* in Subset Groups to properly export them.

[mrakgr]

Now that I got this out of the way, why is Clarisse complaining about the asset being left-handed? How do I export it as a right handed asset instead?

[mrakgr]

On 16. 03. 2022. at 8:47 PM, dleonhardt said:

You need to import your geometry into the Stage context, apply the materials and export from the Stage context. The SOP Level USD Export doesn't know what to do with 'shop_materialpath'.

When I use Scene Import (All), export it that way as USD, and import it in Clarisse, the entire scene graph ends up being flattened, and I get thousands of mesh_0_x objects cluttering my scene. So I've tried the approach of separating out the objects individually and naming the nodes. But that still results in the scene graph not being exported. Is there a way to export the scene graph as well so I can get the objects nearly arranged into contexts?

Edited March 18, 2022 by mrakgr