USDZ Export Issue – Incorrect Metallic/Roughness Rendering, Overly Glossy Appearance, and Flipped Normals

[Arek3D]

Hi, I believe there’s an issue with the USDZ exporter, specifically related to how it handles roughness values in the metallic/roughness workflow. When I export the same model to the GLB format, everything looks correct. However, exporting to USDZ from the same scene results in a visually different model: it appears overly glossy with intense white reflections and lacking any roughness.

When viewed on Mac or AR mode on iPad, the model has no visible roughness and is excessively reflective.

Tested on:
MacBook Pro 2018 (macOS 13.2.1)
iPad Pro (11-inch) MTXN2FD/A (iPadOS 18.5)

Moreover, in this particular demo model, it seems, that normals are flipped, which is I think a different bug.

Exporter:

Babylon.js docs

An example of problematic model:

Babylon.js Playground

You can also use an online viewer, where you can see the flipped textures and the lack of roughness.

USDZ Online Viewer

[Deltakosh]

cc @alexchuber

[alexchuber]

Thanks for the report! Will investigate soon.

The USDZ exporter is fairly new and limited in its PBR capabilities, but I wouldn’t expect the metal/rough values of a Babylon PBRMaterial to export like that. And the flipped orientation is certainly wrong