Brax MuJoCo Collision Cylinder, Ellipsoid #2811

pachoremayuresh · 2025-08-20T07:27:45Z

pachoremayuresh
Aug 20, 2025

Intro

Hi!
I am Mayuresh Pachore. I am a master's student atthe University of Bologna Currently doing my research internship at SAXION SMART LAB Enschede.
I am Using MuJoCo For Reinforcement Learning. And I am using Brax for it.

My setup

in drone.xml

<worldbody>
    <body name="drone" pos="0 0 1.27175" euler="0 0 0.523599">  <!--0.27175-->
        <joint name="drone_x" type="slide" axis="1 0 0"/>
        <joint name="drone_y" type="slide" axis="0 1 0"/>
        <joint name="drone_z" type="slide" axis="0 0 1"/>
        <inertial pos="0 0 0" mass="2" diaginertia="0.06185585085 0.46467853407 0.47162119244"/>
        <geom type="mesh" mesh="base" material="grey"/>
        <geom name="arm" type="cylinder" size="0.01 0.3475" pos="0.300943827 -0.17375 0.0" euler="-2.61799 1.5708 0" material = "white"/>
        <geom name="End_Effector" type="sphere" size="0.01" pos="0.60188765563 -0.3475 0.0" euler="0 0 -0.523599" material = "red"/>
        <geom name="prop1" type="ellipsoid" size=".13 .13 .01" pos="0.38998 0 0" euler="0.34906585 0 0" material="yellow"/>
        <geom name="prop2" type="ellipsoid" size=".13 .13 .01" pos="0.195 0.3377 0" euler="-0.34906585 0 1.0472" material="pink"/>
        <geom name="prop3" type="ellipsoid" size=".13 .13 .01" pos="-0.195 0.3377 0" euler="0.34906585 0 2.0944" material="purple"/>
        <geom name="prop4" type="ellipsoid" size=".13 .13 .01" pos="-0.38998 0 0" euler="0.34906585 0 0" material="green"/>
        <geom name="prop5" type="ellipsoid" size=".13 .13 .01" pos="-0.195 -0.3377 0" euler="-0.34906585 0 1.0472" material="orange"/>
        <geom name="prop6" type="ellipsoid" size=".13 .13 .01" pos="0.195 -0.3377 0" euler="0.34906585 0 2.0944" material="blue"/>
        <site name="thrust1" pos="0.38998 0 0" euler="0.34906585 0 0"/>
        <site name="thrust2" pos="0.195 0.3377 0" euler="-0.34906585 0 1.0472"/>
        <site name="thrust3" pos="-0.195 0.3377 0" euler="0.34906585 0 2.0944"/>
        <site name="thrust4" pos="-0.38998 0 0" euler="0.34906585 0 0"/>
        <site name="thrust5" pos="-0.195 -0.3377 0" euler="-0.34906585 0 1.0472"/>
        <site name="thrust6" pos="0.195 -0.3377 0" euler="0.34906585 0 2.0944"/>
        <site name="End_Effector_Sensor" pos="0.60188765563 -0.3475 0.0" euler="0 0 -0.523599"/>
        <site name="CoM"/>
        <camera name="parallel_cam" mode="targetbody" target='drone' pos="1.80943827 2.17375 0.5" euler="1.32582133 0  2.61799"/>
    </body> 
</worldbody>

in scene.xml

<contact>
    <pair geom1="End_Effector" geom2="Wall" solref="-1000 0" solimp="0.99 0.99 0.0001 0.5 2" friction="1 1 0.005 0.0001 0.0001"/>
</contact>


<worldbody>
    <light pos="0 0 1.5" dir="0 0 -1" directional="true"/>
    <geom name="floor" size="0 0 0.05" type="plane" material="groundplane"/>
    <geom name="Wall" pos="0.905 0 10" size="0.2 10.0 10" type="box" material="dark_grey"/>
</worldbody>

<sensor>
    <contact name="contact_sensor" geom1="End_Effector" geom2="Wall" data="found force torque dist pos"/>
</sensor>

My question

##I am receiving an error

File ~/.local/lib/python3.10/site-packages/mujoco/mjx/_src/io.py:111, in put_model(m, device, _full_compat)
109 if not collision_driver.has_collision_fn(t1, t2) and not _full_compat:
110 t1, t2 = mujoco.mjtGeom(t1), mujoco.mjtGeom(t2)
--> 111 raise NotImplementedError(f'({t1}, {t2}) collisions not implemented.')
112 # margin/gap not supported for meshes and height fields
113 no_margin = {mujoco.mjtGeom.mjGEOM_MESH, mujoco.mjtGeom.mjGEOM_HFIELD}

NotImplementedError: (mjtGeom.mjGEOM_CYLINDER, mjtGeom.mjGEOM_BOX) collisions not implemented.

The file works fine in MuJoCo Viewer but when I am trying to implement that in brax I get this error.

Is it because MuJoCo MJCF has not implemented the CYLINDER and ELLIPSOID collision functions?
Looking Forward to understanding on this.

Confirmations

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

kevinzakka · 2025-08-20T23:11:30Z

kevinzakka
Aug 20, 2025
Collaborator

Hi @pachoremayuresh, see the MJX documentation for a list of what collisions are supported.

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Brax MuJoCo Collision Cylinder, Ellipsoid #2811

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Brax MuJoCo Collision Cylinder, Ellipsoid #2811

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pachoremayuresh Aug 20, 2025

Intro

My setup

in drone.xml

in scene.xml

My question

Confirmations

Replies: 1 comment

Uh oh!

kevinzakka Aug 20, 2025 Collaborator

pachoremayuresh
Aug 20, 2025

kevinzakka
Aug 20, 2025
Collaborator