Bugs found when building MuJuCo with USD

[Pap-let]

Intro

Hi!

I am a graduate student at ECNU, I use MuJoCo for my research on EmbodiedAI.

My setup

MuJoCo with USD on arm64 MacOS 26.1

What's happening? What did you expect?

I built the mujuco myself with the MUJOCO_WITH_USD=True and expecting to drag and load usd files in the simulate.cc.
Here are some bugs I have met with.

1. The official documentation on MuJuCo does not match the latest building pipeline, the document is still using USD_DIR to specify the self-built USD lib instead of the lastest pxr_DIR and does not mention that the user need to set MUJOCO_WITH_USD to True in order to build mujuco with usd.
2. There seem to be some issue on the mjUSEUSD variable since I didn't find where it is defined in the whole project but its defination is checked in many src files such as "simulate/main.cc". Even if I set MUJOCO_WITH_USD to True I still can't drag and load usd files in simulate.cc. The simulate.cc won't print OpenUSD version as it is assumed to. It will try to load a usd file as an xml and throw XML Error because mjUSEUSD is never defined.
3. According to the github update log there should be no need to manually set plugin info with export PXR_PLUGINPATH_NAME=/usr/local/lib/mujocoUsd/resources/*/plugInfo.json, the official documentation needs an update.

Steps for reproduction

1. build the mujuco with usd using

cmake .. -DCMAKE_BUILD_TYPE=Release -DMUJOCO_WITH_USD=True
cmake --build . -j 30
sudo cmake --install . 

2. run simulate and try drag and load a usd file, it will throw you some error with XML.

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[SagarJadhav30]

I’m looking into this and plan to submit a patch + doc update. Assigning to myself.

[SagarJadhav30]

cmake .. -DCMAKE_BUILD_TYPE=Release -DMUJOCO_WITH_USD=ON
cmake --build . -j
sudo cmake --install .
Then launch simulate and drag a .usd file → it is treated as XML and fails.
Environment - macOS arm64
MuJoCo built from source
OpenUSD built from source

@Pap-let I’m happy to help test or submit a PR once the intended behavior of mjUSEUSD and the build flags is clarified.

[Pap-let]

cmake .. -DCMAKE_BUILD_TYPE=Release -DMUJOCO_WITH_USD=ON cmake --build . -j sudo cmake --install . Then launch simulate and drag a .usd file → it is treated as XML and fails. Environment - macOS arm64 MuJoCo built from source OpenUSD built from source

@Pap-let I’m happy to help test or submit a PR once the intended behavior of mjUSEUSD and the build flags is clarified.

I have successfully built MuJoco with USD by annotating all the mjUSEUSD flags with DMUJOCO_WITH_USD=ON. It could serve as a temporary way to build the USD plugin.