[C API] Meshes fail to load: "Error: no decoder found for mesh file"

[davidhozic]

Intro

Hi!

I am a researcher at University of Ljubljana, I use MuJoCo for my research.

My setup

MuJoCo-3.6.0 (C API), Linux Fedora 43, amd64.

What's happening? What did you expect?

Trying to load a model with meshes fails, with the error message:

Error: no decoder found for mesh file

This happens both with actual code and also with the compile sample, which is part of official releases inside the bin/ directory.

The same model I tested (which isn't the one below) worked fine in 3.3.7.

Update:
This happens because the decoding logic is moved into a plugin library (libstl_decoder.so). This is a breaking dependency change and it doesn't seem to be documented anywhere.

Steps for reproduction

Use the compile sample from the official 3.6.0 release and try to load in the bottom model.

Minimal model for reproduction

The STL file is provided in the ZIP file (STL files aren't allowed on GitHub issues?): bug-mujoco-meshes.zip

<mujoco>
    <asset>
        <mesh file="bug-mujoco-meshes.stl"/>
    </asset>

    <worldbody>
        <geom type="mesh" mesh="bug-mujoco-meshes"/>
    </worldbody>
</mujoco>

Code required for reproduction

Not relevant.

Confirmations

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