Hello everyone,
i am interested in building a usd scene from scratch using several fbx assets.
The goal is to be able to share this with someone using Cinema4d.

i ve seen the tutorials about Solaris and usd but i havent yet understood how you would do what i am describing exactly.

1) how can i import assets fbx obj to build a usd scene? do they also need to be usd files if we want to update them?

2) the materials have to be setup for a specific renderer? if it will be rendered in Redshift cinema4d should i also have redshift in houdini to setup materials?

3) are textures embedded or will i need to have folders containing textures along with my final usd file?

Is there a tutorial that can help me out with these specific questions?

papsphilip
1) how can i import assets fbx obj to build a usd scene? do they also need to be usd files if we want to update them?

USD can't read fbx directly, so I think you would need to import into Houdini obj/sop and then import into lops using a sceneimport or sopimport lop. Once in lops, if you wanted, you could save your assets as usd and be free of fbx. If the fbx assets are going to keep changing on the other hand you can keep the sceneimport/sopimport stuff around to pick up any updates.

I don't know how tied you are to fbx but it's worth mentioning that USD can read Alembic directly. So if you can export your assets as Alembic instead you may (or may not) have an easier time getting things into lops. And of course if the assets could be exported by USD in the first place that would be even less work.

papsphilip
2) the materials have to be setup for a specific renderer? if it will be rendered in Redshift cinema4d should i also have redshift in houdini to setup materials?

Yes, renderers have their own materials for final renders. USD does have a cross-renderer Preview Surface that all renderers are supposed to be able render in an identical way. But the preview surface is pretty limited and supports a very small set of utility nodes (iirc just 2d texture, 2d placement, and primvar reader). MaterialX is another potential option that hopes to standardize shading networks across renderers. MaterialX is kind of on the bleeding edge so ymmv and it's probably safest to assume you'll need Redshift running in lops.

papsphilip
3) are textures embedded or will i need to have folders containing textures along with my final usd file?

USD files don't contain texture data so yes you'll probably need to bundle up textures as well. There is a usdz file format that is basically a zip file that can be expanded on the fly with everything kept in memory. But it adds complexity and I believe is mostly intended for remote client/server type exchange. For casual usage I imagine it's probably easier to just manually zip/unzip in the normal way.

papsphilip
Is there a tutorial that can help me out with these specific questions?

Sorry I'm not sure how much stuff there is around importing from fbx or shading with Redshift. Maybe others know.

One last thing, does Cinema4d have solid USD reading capabilities now? I'm asking b/c what you'll get out of lops are USD files, not fbx. Getting lops back out as fbx would be another bunch of work and I don't know offhand how well the shading would translate.

thank you very much for the thorough reply. i have to test all that. it would be awesome to have the ability to setup materials even if you don't have a redshift or arnold etc subscription, like a general purpose material description.

Cinema 4d R23 and above can import and export as far as i can see in the documentation but i haven't tried it yet

https://help.maxon.net/c4d/en-us/#html/FUSDIMPORTER-USDIMPORTER_GROUP.html?Highlight=usd [help.maxon.net]

i am not sure how you can modify the file though. it would be helpful if i could do the layout in houdini LOPs --> usd export --> import to cinema and then apply redshift materials

papsphilip
i am not sure how you can modify the file though. it would be helpful if i could do the layout in houdini LOPs --> usd export --> import to cinema and then apply redshift materials

Yeah looking at the documentation it seems like you would be able to import the USD as USD using the bridge mode, or import as native Cinema 4d. I don't know what editing functionality there is in the bridge mode, but as a native Cinema 4d scene you should be able to do anything you want so long as it import/translates correctly in the first place. Keeping the scene as USD is nice though because USD uses a non destructive layer approach, so it's probably worth trying the bridge mode as well.