Error: engine error: edge ordering is incoherent between flex and plugin / mujoco.elasticity.solid

[shunsei-t]

Hi,

I'm a student and I'm trying to use MuJoCo for elastic solid simulation.

I'm looking for some help with troubleshooting some errors.

Here is a model which explains my question:

minimal XML

<mujoco>
  <extension>
    <plugin plugin="mujoco.elasticity.solid"/>
  </extension>

  <worldbody>

    <flexcomp name="softlimb" dim="2" type="mesh" file="test.obj">
      <plugin plugin="mujoco.elasticity.solid">
        <config key="poisson" value="0.3"/>
        <config key="young" value="1e8"/>
        <config key="damping" value="0.002"/>
      </plugin>
    </flexcomp>
  </worldbody>
</mujoco>

minimal Python code

import time
import mujoco.viewer

model = mujoco.MjModel.from_xml_path("assets/flex.xml")
data = mujoco.MjData(model)
n_steps = 5

with mujoco.viewer.launch_passive(model, data) as viewer:
    start = time.time()
    while True:
        step_start = time.time()
        for _ in range(n_steps):
            mujoco.mj_step(model, data)
        viewer.sync()
        time_until_next_step = model.opt.timestep - (time.time() - step_start)
        if time_until_next_step > 0:
            time.sleep(time_until_next_step)

obj file
obj_files.zip

Here is a error message.

ValueError: Error: engine error: edge ordering is incoherent between flex and plugin

and I saw this issue.
#1647