Is there a plan for a USD importer?

[psclklnk]

After discovering the USDExporter just some days ago while browsing through the documentation and codebase, I was wondering whether there are plans to implement a similar feature for importing USD scenes into MuJoCo for simulation. Or is this task seen as too ambiguous due to the expressiveness of USD (and the many ways of describing scenes in it)?

[Balint-H]

What kind of use cases do you think would there be for a USD importer? Authoring/editing scenes in something like Blender?

[ProNeverFake]

I'm now trying robocasa & robosuite that are based on mujoco. Robocasa applies yaml files as layout descriptions, setting up the poses of walls, floors, fixtures in the scene (cabinets, microwaves and other objects that get fixed joints to the world body), while a user-friendly GUI for object importing and adjusting is missing.
A straightforward idea is to leverage other utility-providers, like unity, blender and Isaac sim, and import the modified scene file back to mujoco for further usage. In this usecase I think a USD importer is necessary.

[psclklnk]

Yes exactly I was asking that question because in combination with a feature complete USD exporter, a corresponding importer would significantly ease interfacing with tools such as Blender.

For example, you could design the (collision and visual) meshes and materials for your simulation in Blender, then hand that off to MuJoCo for simulation and then either render it in Blender or potentially use a different rendering engine that supports USD.

All in all, it would make MuJoCo more of a first class of a landscape of very sophisticated 3D modeling and rendering tools.

[ProNeverFake]

I would like to know the main difficulty in conducting such a conversion. In my understanding, a USD file offers verbose information about the scene, and the only difficulty lies in finding the corresponding definitions, splitting the assets and the "skeletons", and organizing the resources accordingly.
It would be great if you could further show me the core problem in developing such a tool/functionality. If there is a plan for development, I'm willing to contribute.

[psclklnk]

I think you're right about the high-level picture: creating an importer is mostly about converting data structures.

I was asking here in the forum instead of getting my hands dirty right away because of two reasons:

• I have limited experience with USD and the way how it is intended to be used (I e.g. do not know if there are multiple ways of achieving the same scene with different descriptions, and if in this case there is one description style which is more commonly used)
• From the few interactions I had with USD (using IsaacSim), I remember that Nvidia created extensions to the default USD language to specify additional properties that were important to the simulation using PhysX.

Therefore I think that there is a conversation to be had about what structure to expect from these USD files that should be imported, ideally taking into account the interoperability with existing tools.