NotImplementedError: rne_postconstraint not implemented with equality constraints: connect, weld.

[HuNingHe]

Intro

I get error:

Traceback (most recent call last):
File "/home/zy/a2_model/model/xml/romela/test.py", line 16, in
mjx_model = mjx.put_model(mj_model)
^^^^^^^^^^^^^^^^^^^^^^^
File "/home/zy/miniconda3/envs/mujoco_playground/lib/python3.12/site-packages/mujoco/mjx/_src/io.py", line 160, in put_model
raise NotImplementedError(
NotImplementedError: rne_postconstraint not implemented with equality constraints: connect, weld.

My setup

When I run code below:
mujoco>3.0.1

import mujoco
from mujoco import mjx
import os

script_dir = os.path.dirname(os.path.abspath(__file__))
xml = script_dir + "/romela_scene.xml"
print("xml path:", xml)

mj_model = mujoco.MjModel.from_xml_path(xml)
mj_data = mujoco.MjData(mj_model)
renderer = mujoco.Renderer(mj_model)

mjx_model = mjx.put_model(mj_model)
mjx_data = mjx.put_data(mj_model, mj_data)

print(mj_data.qpos, type(mj_data.qpos))
print(mjx_data.qpos, type(mjx_data.qpos), mjx_data.qpos.devices())

this xml works fine in mujoco

My question

how to add equality constraint in mjx

Minimal model and/or code that explain my question

If you encountered the issue in a complex model, please simplify it as much as possible (while still reproducing the issue).

Model:

minimal XML

<mujoco>
  <worldbody>
    <light pos="0 0 1"/>
    <geom type="sphere" size="1" rgba="1 0 0 1"/>
  </worldbody>
</mujoco>

Code:

import mujoco
import mediapy as media
model = mujoco.MjModel.from_xml_string(xml)
data = mujoco.MjData(model)

with mujoco.Renderer(model) as renderer:
  mujoco.mj_forward(model, data)
  renderer.update_scene(data)

  media.show_image(renderer.render())

Confirmations

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

[thowell]

MJX support for equality constraints is listed in Feature Parity. However, there are certain sensor and equality constraint combinations that MJX does not currently support. Please see this check in io.py for more details.

Support for these sensor and equality constraint combinations could be added to MJX by updating rne_postconstraint to include the necessary equality constraint terms. For reference, the MuJoCo implementation is mj_rnePostConstraint.