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Description
Intro
Hi!
I am a individual researcher, I use MuJoCo for my research on robotic manipulation.
I started with a very simple example of having a square piece of soft material.
I tried to simulate the random initial state of the soft piece so I use euler property.
While when the euler was set "0 0 0" it's working well, it's totally broken if it was set to "10 0 0".
My setup
MuJoCo==3.3.0, Python API, Running inside Docker: FROM nvidia/cuda:12.2.2-devel-ubuntu22.04
What's happening? What did you expect?
python -m mujoco.viewer --mjcf=./models/cloth.xml
The simulation diverges quickly with logs:
WARNING: Nan, Inf or huge value in QACC at DOF 0. The simulation is unstable. Time = 0.0870.
Steps for reproduction
- Load the model below.
- Run the code below.
Minimal model for reproduction
<mujoco model="simple_square_soft_stable">
<compiler angle="degree"/>
<option timestep="0.001" gravity="0 0 -9.81">
<flag energy="enable" contact="enable" gravity="enable"/>
</option>
<size njmax="5000" nconmax="1000"/>
<asset>
<texture name="grid" type="2d" builtin="checker"
rgb1=".2 .3 .4" rgb2=".1 0.15 0.2"
width="512" height="512" mark="cross" markrgb=".8 .8 .8"/>
<material name="groundmat" texture="grid" texrepeat="2 2"/>
<material name="softmat" rgba="0.8 0.2 0.2 1.0" specular="0.3" shininess="0.5"/>
</asset>
<worldbody>
<light diffuse=".8 .8 .8" pos="0 0 3" dir="0 0 -1"/>
<geom name="ground" type="plane" size="2 2 0.1" pos="0 0 0" material="groundmat"/>
<!-- More stable soft body configuration -->
<flexcomp name="square" type="grid" count="10 10 1" spacing="0.04 0.04 0.04" pos="0 0 1" euler="10 0 0"
radius="0.005" mass="1.0" material="softmat">
<contact solref="0.02 0.5" solimp="0.9 0.95 0.001" friction="0.7 0.1 0.1" condim="3" internal="true"/>
<edge damping="0.5"/>
<elasticity poisson="0.3" young="1000"/>
</flexcomp>
<!-- Ball for interaction -->
<!--<body name="ball" pos="0.0 0 0.6"> -->
<!-- <geom type="sphere" size="0.05" density="500" rgba="0.2 0.6 0.8 1"/> -->
<!--</body> -->
</worldbody>
</mujoco>
Confirmations
- I searched the latest documentation thoroughly before posting.
- I searched previous Issues and Discussions, I am certain this has not been raised before.