Unsteady contacts: objects repel upon contact. #2195

Shiduo-zh · 2024-10-30T16:16:41Z

Shiduo-zh
Oct 30, 2024

Intro

Hi!

I am a graduate student at Fudan University, I use MuJoCo for my research on manipulation simulation.

My setup

mujuco 3.2.2
python 3.10.14
ubuntu 20.04

My question

When using MuJoCo for simulation, I encountered some strange collision phenomena. When a card comes into contact with the tablecloth, there are occasional instances where the card is directly bounced far away upon contact with the other object.

Based on previous issues I’ve searched, I tried adjusting parameters such as impratio(e.g. impratio from 1 to 50), enable multiccd, solref(in this setting, "0.001 1") and solimp(0.998 0.998 0.001), but the problem persists. And I attach my setting and asset in the following section.

I would like to understand:

1.	What causes this abnormal contact?
2.	What other parameters can be adjusted to avoid this type of abnormal mesh-mesh collision?

Thanks for your patience and response!

Failure Case:
The placemat is placemat_5.xml
(in the 40th second, all cards flew away.)

success_False.mp4

Success Case:
The placemat is placemat_6.xml

success_True.mp4

Minimal model and/or code that explain my question

global config

<mujoco model="BaseScene">
    <compiler angle="radian"/>
    <size memory="5000M"/>
    <option impratio="1"
            timestep="0.002" 
            density="1.225" 
            viscosity="1.8e-5"  
            integrator="implicitfast">
        <flag multiccd="enable"/>
    </option>
    <include file="../common/cameras.xml"/>
    <statistic extent="0.5" center="0 -.5 0"/>
    <visual>
        <!-- <map fogend="1" shadowclip="0.01"/> -->
        <!-- <headlight diffuse="0.2 0.2 0.2" ambient="0.3 0.3 0.3" specular="0 0 0" /> -->
        <quality shadowsize="8192"/>
        <global offwidth="1280" offheight="960"/>
    </visual>
    <worldbody>
    </worldbody>

</mujoco>

assets files
placemat_.zip
poker.zip
other xml files

placemat_6.xml

<mujoco model="placemat_6">
  <compiler angle="radian"/>
  <default>
    <default class="visual">
      <geom group="2" type="mesh" contype="0" conaffinity="0"/>
    </default>
    <default class="collision">
      <geom group="3" type="mesh" solref="0.001 1" solimp="0.998 0.998 0.001"/>
    </default>
    <default class="keypoint">
      <site type="sphere" size="0.01" group="3" rgba="1 0 0 1"/>
    </default>
  </default>
  <asset>
    <texture type="2d" name="material_0" file="material_0.png"/>
    <material name="material_0" texture="material_0" specular="0.4000000000000001" shininess="0.001"/>
    <mesh file="placemat_6.obj" scale="0.35 0.35 0.35"/>
    <mesh file="placemat_6_collision_0.obj" scale="0.35 0.35 0.35"/>
  </asset>
  <worldbody>
    <body name="placemat_6" euler="0 0 1.57">
      <geom material="material_0" mesh="placemat_6" class="visual"/>
      <geom mesh="placemat_6_collision_0" rgba="0.920239868558051 0.23639053077114314 0.03807289455627372 1" class="collision"/>
    </body>
    <site class="keypoint" pos="0.15 0.12 0"/>
    <site class="keypoint" pos="-0.15 -0.12 0"/>
  </worldbody>
</mujoco>

placemat_5.xml

<mujoco model="placemat_5">
  <compiler angle="radian"/>
  <default>
    <default class="visual">
      <geom group="2" type="mesh" contype="0" conaffinity="0"/>
    </default>
    <default class="collision">
      <geom group="3" type="mesh" solref="0.001 1" solimp="0.998 0.998 0.001"/>
    </default>
    <default class="keypoint">
      <site type="sphere" size="0.01" group="3" rgba="1 0 0 1"/>
    </default>
  </default>
  <asset>
    <texture type="2d" name="material_0" file="material_0.png"/>
    <material name="material_0" texture="material_0" specular="0.4000000000000001" shininess="0.001"/>
    <mesh file="placemat_5.obj" scale="0.5 0.5 0.5"/>
    <mesh file="placemat_5_collision_0.obj" scale="0.5 0.5 0.5"/>
    <mesh file="placemat_5_collision_1.obj" scale="0.5 0.5 0.5"/>
    <mesh file="placemat_5_collision_2.obj" scale="0.5 0.5 0.5"/>
  </asset>
  <worldbody>
    <body name="placemat_5" euler="">
      <geom material="material_0" mesh="placemat_5" class="visual"/>
      <geom mesh="placemat_5_collision_0" rgba="0.9025340388748923 0.16195453644088398 0.9843349143653423 1" class="collision"/>
      <geom mesh="placemat_5_collision_1" rgba="0.49885567005984965 0.6724431508315711 0.7200880766743581 1" class="collision"/>
      <geom mesh="placemat_5_collision_2" rgba="0.6877420702161725 0.9528137096444969 0.9552802145832006 1" class="collision"/>
    </body>
    <site class="keypoint" pos="0.15 0.15 0"/>
    <site class="keypoint" pos="-0.15 -0.15 0"/>
  </worldbody>
</mujoco>

poker

<mujoco model="card">
  <default>
    <geom solref=".5e-4" solimp="0.9 0.99 1e-4" fluidcoef="0.5 0.25 0.5 2.0 1.0"/>
    <default class="card">
      <geom type="mesh" mesh="card" mass="1.84e-4" fluidshape="ellipsoid" contype="0" conaffinity="0"/>
    </default>
    <default class="collision">
      <geom type="box" mass="0" size="0.047 0.032 .001" group="3" friction="1" solref="0.001 1" solimp="0.998 0.998 0.001"/>
    </default>
    <default class="grasppoint">
        <site type="sphere" size="0.01" group="4" rgba="0 0 1 1"/>
    </default>
  </default>
  <asset>
    <mesh name="card" file="./assets/card.obj"/>

    <texture type="2d" file="./assets/2_of_clubs.png"/>
    <material name="2_of_clubs" texture="2_of_clubs"/>

    <texture type="2d" file="./assets/2_of_diamonds.png"/>
    <material name="2_of_diamonds" texture="2_of_diamonds"/>

    <texture type="2d" file="./assets/2_of_hearts.png"/>
    <material name="2_of_hearts" texture="2_of_hearts"/>

    <texture type="2d" file="./assets/2_of_spades.png"/>
    <material name="2_of_spades" texture="2_of_spades"/>

    <texture type="2d" file="./assets/3_of_clubs.png"/>
    <material name="3_of_clubs" texture="3_of_clubs"/>

    <texture type="2d" file="./assets/3_of_diamonds.png"/>
    <material name="3_of_diamonds" texture="3_of_diamonds"/>

    <texture type="2d" file="./assets/3_of_hearts.png"/>
    <material name="3_of_hearts" texture="3_of_hearts"/>

    <texture type="2d" file="./assets/3_of_spades.png"/>
    <material name="3_of_spades" texture="3_of_spades"/>

    <texture type="2d" file="./assets/4_of_clubs.png"/>
    <material name="4_of_clubs" texture="4_of_clubs"/>

    <texture type="2d" file="./assets/4_of_diamonds.png"/>
    <material name="4_of_diamonds" texture="4_of_diamonds"/>

    <texture type="2d" file="./assets/4_of_hearts.png"/>
    <material name="4_of_hearts" texture="4_of_hearts"/>

    <texture type="2d" file="./assets/4_of_spades.png"/>
    <material name="4_of_spades" texture="4_of_spades"/>

    <texture type="2d" file="./assets/5_of_clubs.png"/>
    <material name="5_of_clubs" texture="5_of_clubs"/>

    <texture type="2d" file="./assets/5_of_diamonds.png"/>
    <material name="5_of_diamonds" texture="5_of_diamonds"/>

    <texture type="2d" file="./assets/5_of_hearts.png"/>
    <material name="5_of_hearts" texture="5_of_hearts"/>

    <texture type="2d" file="./assets/5_of_spades.png"/>
    <material name="5_of_spades" texture="5_of_spades"/>

    <texture type="2d" file="./assets/6_of_clubs.png"/>
    <material name="6_of_clubs" texture="6_of_clubs"/>

    <texture type="2d" file="./assets/6_of_diamonds.png"/>
    <material name="6_of_diamonds" texture="6_of_diamonds"/>

    <texture type="2d" file="./assets/6_of_hearts.png"/>
    <material name="6_of_hearts" texture="6_of_hearts"/>

    <texture type="2d" file="./assets/6_of_spades.png"/>
    <material name="6_of_spades" texture="6_of_spades"/>

    <texture type="2d" file="./assets/7_of_clubs.png"/>
    <material name="7_of_clubs" texture="7_of_clubs"/>

    <texture type="2d" file="./assets/7_of_diamonds.png"/>
    <material name="7_of_diamonds" texture="7_of_diamonds"/>

    <texture type="2d" file="./assets/7_of_hearts.png"/>
    <material name="7_of_hearts" texture="7_of_hearts"/>

    <texture type="2d" file="./assets/7_of_spades.png"/>
    <material name="7_of_spades" texture="7_of_spades"/>

    <texture type="2d" file="./assets/8_of_clubs.png"/>
    <material name="8_of_clubs" texture="8_of_clubs"/>

    <texture type="2d" file="./assets/8_of_diamonds.png"/>
    <material name="8_of_diamonds" texture="8_of_diamonds"/>

    <texture type="2d" file="./assets/8_of_hearts.png"/>
    <material name="8_of_hearts" texture="8_of_hearts"/>

    <texture type="2d" file="./assets/8_of_spades.png"/>
    <material name="8_of_spades" texture="8_of_spades"/>

    <texture type="2d" file="./assets/9_of_clubs.png"/>
    <material name="9_of_clubs" texture="9_of_clubs"/>

    <texture type="2d" file="./assets/9_of_diamonds.png"/>
    <material name="9_of_diamonds" texture="9_of_diamonds"/>

    <texture type="2d" file="./assets/9_of_hearts.png"/>
    <material name="9_of_hearts" texture="9_of_hearts"/>

    <texture type="2d" file="./assets/9_of_spades.png"/>
    <material name="9_of_spades" texture="9_of_spades"/>

    <texture type="2d" file="./assets/10_of_clubs.png"/>
    <material name="10_of_clubs" texture="10_of_clubs"/>

    <texture type="2d" file="./assets/10_of_diamonds.png"/>
    <material name="10_of_diamonds" texture="10_of_diamonds"/>

    <texture type="2d" file="./assets/10_of_hearts.png"/>
    <material name="10_of_hearts" texture="10_of_hearts"/>

    <texture type="2d" file="./assets/10_of_spades.png"/>
    <material name="10_of_spades" texture="10_of_spades"/>

    <texture type="2d" file="./assets/ace_of_clubs.png"/>
    <material name="ace_of_clubs" texture="ace_of_clubs"/>

    <texture type="2d" file="./assets/ace_of_diamonds.png"/>
    <material name="ace_of_diamonds" texture="ace_of_diamonds"/>

    <texture type="2d" file="./assets/ace_of_hearts.png"/>
    <material name="ace_of_hearts" texture="ace_of_hearts"/>

    <texture type="2d" file="./assets/ace_of_spades.png"/>
    <material name="ace_of_spades" texture="ace_of_spades"/>

    <texture type="2d" file="./assets/black_joker.png"/>
    <material name="black_joker" texture="black_joker"/>

    <texture type="2d" file="./assets/red_joker.png"/>
    <material name="red_joker" texture="red_joker"/>

    <texture type="2d" file="./assets/jack_of_clubs.png"/>
    <material name="jack_of_clubs" texture="jack_of_clubs"/>

    <texture type="2d" file="./assets/jack_of_diamonds.png"/>
    <material name="jack_of_diamonds" texture="jack_of_diamonds"/>

    <texture type="2d" file="./assets/jack_of_hearts.png"/>
    <material name="jack_of_hearts" texture="jack_of_hearts"/>

    <texture type="2d" file="./assets/jack_of_spades.png"/>
    <material name="jack_of_spades" texture="jack_of_spades"/>

    <texture type="2d" file="./assets/king_of_clubs.png"/>
    <material name="king_of_clubs" texture="king_of_clubs"/>

    <texture type="2d" file="./assets/king_of_diamonds.png"/>
    <material name="king_of_diamonds" texture="king_of_diamonds"/>

    <texture type="2d" file="./assets/king_of_hearts.png"/>
    <material name="king_of_hearts" texture="king_of_hearts"/>

    <texture type="2d" file="./assets/king_of_spades.png"/>
    <material name="king_of_spades" texture="king_of_spades"/>

    <texture type="2d" file="./assets/queen_of_clubs.png"/>
    <material name="queen_of_clubs" texture="queen_of_clubs"/>

    <texture type="2d" file="./assets/queen_of_diamonds.png"/>
    <material name="queen_of_diamonds" texture="queen_of_diamonds"/>

    <texture type="2d" file="./assets/queen_of_hearts.png"/>
    <material name="queen_of_hearts" texture="queen_of_hearts"/>

    <texture type="2d" file="./assets/queen_of_spades.png"/>
    <material name="queen_of_spades" texture="queen_of_spades"/>
  </asset>
</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.

Answered by yuvaltassa

Oct 31, 2024

When colliding small and fast things, you need a smaller timestep, did you try this?

View full answer

Shiduo-zh · 2024-10-30T17:29:17Z

Shiduo-zh
Oct 30, 2024
Author

And another video for example. I load the env with dm_control. Whenever the env is reset, only textures are randomized, the entities are the same.

collision_error.mp4

0 replies

yuvaltassa · 2024-10-31T11:09:44Z

yuvaltassa
Oct 31, 2024
Maintainer

When colliding small and fast things, you need a smaller timestep, did you try this?

1 reply

Shiduo-zh Oct 31, 2024
Author

Thank you for your prompt response! That is indeed the case. Previously, I had adjusted the Timestep to 1e-3, but it still failed. This time, I adjusted it to 1e-4, and the issue almost no longer occurs. I will make a trade-off between stability and speed！

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Unsteady contacts: objects repel upon contact. #2195

Shiduo-zh Oct 30, 2024

Intro

My setup

My question

Minimal model and/or code that explain my question

Confirmations

Replies: 2 comments · 1 reply

Shiduo-zh Oct 30, 2024 Author

yuvaltassa Oct 31, 2024 Maintainer

Shiduo-zh Oct 31, 2024 Author

Shiduo-zh
Oct 30, 2024

Replies: 2 comments 1 reply

Shiduo-zh
Oct 30, 2024
Author

yuvaltassa
Oct 31, 2024
Maintainer

Shiduo-zh Oct 31, 2024
Author