Objects missing when converting GLB to USD.

[jaraujo98]

I am trying to convert a GLB file to USD using the mesh converter tool. My goal is to use it as a scene for training agents with vision. I have an RTX 3090, so I'm constrained to using IsaacSim 4.5 and IsaacLab 2.1. I run the mesh converter tool as

uv run scripts/tools/convert_mesh.py assets/scene.glb assets/processed/scene.usd --make-instanceable --collision-approximation none

(I had to do a few tweaks to the IsaacLab pyproject.toml files in order to be able to use uv directly instead of pip)

The script runs without issue. However, when it gets to this line (IsaacLab/source/isaaclab/isaaclab/sim/converters/mesh_converter.py:_convert_asset link)

prim.GetReferences().AddReference(self.usd_path)

where self.usd_path is the path to the USD file the converter just created, a series of messages like the following one get printed

2025-11-17 00:14:54 [39,549ms] [Warning] [omni.usd] Warning: in _ReportErrors at line 2890 of 
/builds/omniverse/usd-ci/USD/pxr/usd/usd/stage.cpp - In </World/furniture/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d_001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d____001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d______root_001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d______root____027/flower>: Could not open asset @/props/flower.usd@ 
for reference introduced by @.../assets/processed/scene.usd@</World/furniture/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d_001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d____001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d______root_001/
ff0d0a7fe6e2a685cf03bf6ef2e32ae44d79372d______root____027/flower>. 
(instantiating stage on stage @.../assets/processed/scene.usd@ <0x55d5e49275c0>)

The props/flower.usd file exists, and I can load it into Blender, for example. When the IsaacSim window opens, I can see part of the scene, but the objects that triggered warnings are missing. Things that I have tried:

• Converting the GLB to OBJ using Blender and importing the OBJ: it gives me all of the geometry, but I lose the texture information.
• Loading GLB into Blender, fixing non-manifold geometry, exporting to GLB: Issue persists.
• Loading GLB into Blender, simplifying object names, exporting to GLB: Issue persists.
• Exporting the GLB to USD in Blender: Opening the file in IsaacSim loads something, but no geometry is shown in the viewport. I am also concerned that the file generated by Blender is not instanceable, and so not usable for parallel simulation.

My attempts at trying to understand the mechanisms behind USD conversion and their requirements have failed. Any pointers to what I might be doing wrong would be greatly appreciated! Thank you!

[jaraujo98]

I managed to find a workaround using Blender's OBJ export.

1. Load the GLB file into Blender.
2. Save the Blender file.
3. File -> External Data -> Unpack Resources (this saves the texture files somewhere Blender can reference them)
4. OBJ export -> Materials -> Set "Path Mode" to "Copy"

This will create the OBJ file, the MTL file, and all the images required in the folder where the blend file was originally saved. After that, the mesh converter does its job properly.

I still wonder whether @RandomOakForest has any tips for dealing with the original issue, though (updating to IsaacSim 5.1 and IsaacLab 2.3 is a perfectly acceptable answer at this point). 🤔

[jaraujo98]

For more information related to this see this discussion.