Hey,
Sorry for the late reply, my notification settings weren't working properly.
When we view the models in Xcode or Finder, the 3D model always appear black (even when I take those from Apple's website -- see screenshot https://imgur.com/FF0hyC8 ), so I have no idea on how to debug this using my Mac.
We are using Unity's USD plugin to export our models, but even when I use
xcrun usdz_converter
the export does not work.
We have since investigated a bit further and found out that this is only happening to models with a texture applied to the color map -- when the material has a solid color instead of a texture, this bug does not happen.
Here's what happens when we're on iOS 12 (here and here) and on iOS 13 (here and here), when we use this sample URL
Here's the correspondent GLB file with no bugs.
Here's the correspondent FBX/MAT files.
Please let me know if you find anything out or if you need more information.