Prepare USD Files for Upload

Here are some best practices for USD file creation/export for optimal conversion to 3dverse.

Materials

In short,

Use UsdPreviewSurface, not MDL.

3dverse (FTL) uses a PBR material model that maps to UsdPreviewSurface, not MDL. Author your materials with the UsdPreviewSurface shader connected to outputs:surface.

MDL networks (e.g. OmniPBR, outputs:mdl:surface) are not reliably converted, as they are more free form and not necessarily translatable to a PBR material.

That said, common OmniPBR-style constant inputs on mdl:surface shaders (diffuseColor, roughness, metallic, normal, opacity, etc.) are recognized and mapped to the equivalent PBR values, so simple MDL materials using these will still come through.

Textures

In short,

Textures are supported, but the file must be a .usdz.

Texture images bound to UsdPreviewSurface inputs (via UsdUVTexture's inputs:file) are supported and converted.

Texture files are external assets on disk, so the same rule as Multi-file Scenes applies: package the USD file as a .usdz so the textures are bundled inside the archive.

Multi-file Scenes

In short,

Package multi-file scenes as .usdz.

If your USD scene references other USD files upload it as a single .usdz package, not a folder of loose .usd/.usda/.usdc files.

Uploading a main file that references sibling files on disk (folder structure) is not yet supported, but will be in the future. .usdz bundles the main stage and everything it references into one archive, and is supported.

Remote Assets

In short,

If using remote assets, flatten the stage before export. Remote assets aren't supported for now.

Files may reference geometry via a payload pointing to a remote Omniverse asset-store URL (https://...) instead of embedding it.

The converter cannot resolve remote HTTP(S) references, so those meshes will be silently missing.

Flatten the stage during export so payloaded content is baked in the file directly.

Instancing

In short,

Reuse meshes and materials wherever possible (especially for large USD files). Also make use of prototypes.

Use native USD instancing (references) for meshes, materials, that appear more than once in the scene.

For large prim structures that repeat themselves, make use of prototypes (instanceable = true). Each prototype will be converted into a separate scene which will be referenced by the main scene.

Making use of references and protoypes is critical for very large USD files.