This is not an issue for models that are closed volumes, but it will not work well when models have planes or faces that can be visible from both sides.

Double sided rendering is not supported, so all models are rendered single sided.All textures will be mapped using the first UV channel. Multiple UV channels are not supported.Animations will loop endlessly in Quick Look. Animation loop modes are not supported.

Vertex Colors are not supported, so models that depend on Vertex Colors will not look correct.

A workaround could be to duplicate the base color texture in the emission channel.

Quick Look does not have a Shadeless mode, so 3D scans and other models set to Shadeless may look darker than expected.

Point Clouds are not available in USDZ.

For a more exhaustive list, please visit Google's USD from glTF compatibility documentation. Here are some key Sketchfab features that are not supported by USDZ / AR Quick Look. The USDZ format and Apple's AR Quick Look have additional limitations. Since the USDZ file is generated based on the glTF file, anything unsupported by glTF will not be supported by USDZ.

Maximum number vertex attributes per mesh is often set to 16, which can be especially problematic for morph target animations.

Multiple UVs - some engines may force every channel to use the same Texture Coordinates.

Some features are supported by the glTF format itself, but not by certain engines like Unity or Three.js (e.g.

Refraction, Dithered, and Additive transparency (will be converted to Blending).

Some shaders and features are not supported by the glTF specification, so they will not be exported. If you upload a model with 8k textures, all three versions will be generated.

For example, if you upload a model with source textures that are only 512×512 px, we will only generate a GLB with the original textures. We only generate each version when necessary. We also generate several versions of GLB with different maximum texture resolutions: Then, we convert that glTF file into a USDZ file with as much of the same data as possible. Sketchfab takes your original 3D data (meshes, objects, animations, etc.) combined with all the material information in 3D Settings, and converts it to the glTF format using PBR materials and textures. You can also import models directly into your 3D software using Importers.

Export fbx with texture maps from unity