I tried the following process with both Blender and Maya. I'm also running a React app locally so I Quick Look the cube through Safari.
A. OBJ to usdz:
1. Create a cube
2. Unwrap the uv's
3. Export OBJ
4. Paint and export PBR textures from Substance Painter
5. Convert to usdz with usdz_converter and apply only the color map:
xcrun usdz_converter cube.obj cube.usdz -g pCube1 -color_map cube_BaseColor.png -v
B. ABC to usdz:
1,2 same as above.
3. Export Alembic (ABC) and FBX (for Substance Painter)
5,6 same as above.
OBJ -> usdz textures are applied correctly, i.e. each cube face is a different color. ABC to usdz appears scrambled, i.e. the color map is applied but the scale and location is weird.
Upon inspecting the file in Xcode/SceneKit, it seems that upon converting ABC to usdz the texture coordinates are lost. They're definitely there in the Alembic file- could this be a bug?
Does that clarify my process? Any thoughts or solutions?