The SDF plugin is very slow when simulating 200 particles #2504

Wel2018 · 2025-03-17T07:41:17Z

Wel2018
Mar 17, 2025

Intro

Hi!

I am a graduate student, I use MuJoCo for my research on physical simulation.

My setup

MuJoCo 3.3.0, API (C), Ubuntu 22.04

My question

Now I need to create 200 small balls and pour them into a mug. If the SDF plugin is not used, the freely falling balls will be bounced away when they hit the rim of the mug. By referring to the writing methods in model/plugin/sdf/mug.xml and model/plugin/sdf/cow.xml, I can achieve the desired effect, but the simulation speed will become slower and slower over time. My question is: How can I fix this problem to speed up the simulation?

0317cup.mp4

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 Path:

model/plugin/sdf/mug.xml

Model:

minimal XML

<mujoco>
  <compiler texturedir="asset"/>
  
  <extension>
    <plugin plugin="mujoco.sdf.torus">
      <instance name="torus">
        <config key="radius1" value="0.15"/>
        <config key="radius2" value="0.05"/>
      </instance>
    </plugin>
    <plugin plugin="mujoco.sdf.sdflib">
      <instance name="sdf">
        <config key="aabb" value="0"/>
      </instance>
    </plugin>
  </extension>

  <asset>
    <texture name="texspot" type="2d" file="spot.png"/>
    <material name="matspot" texture="texspot"/>
    <!-- <mesh name="spot" file="asset/spot.obj"> -->
    <mesh name="spot" file="../../mug/mug.obj" scale=".2 .2 .2">
      <plugin instance="sdf"/>
    </mesh>
    <mesh name="torus">
      <plugin instance="torus"/>
    </mesh>
  </asset>

  <option sdf_iterations="20" sdf_initpoints="40"/>

  <visual>
    <map force="1000"/>
  </visual>

  <default>
    <geom solref="0.01 1" solimp=".95 .99 .0001" friction="0.5"/>
  </default>

  <statistic meansize="0.2"/>

  <include file="scene.xml"/>
  <size memory="10G"/>
  
  <worldbody>
    <!-- cup -->
    <body euler="90 0 0" pos="0 0 0">
      <geom type="sdf" name="cow1" mesh="spot" material="matspot">
        <plugin instance="sdf"/>
      </geom>
    </body>

    <!-- ball: 2x2x50 -->
    <replicate count="2" offset=".25 0 0">
      <replicate count="2" offset="0 .25 0">
        <replicate count="50" offset="0 0 .25">
          <body pos=".0 .0 10.05">
            <joint type="slide" axis="1 0 0"/>
            <joint type="slide" axis="0 1 0"/>
            <joint type="slide" axis="0 0 1"/>
            <geom type="sphere" size=".12" rgba=".5 .8 .5 1" solref="0.01 1" solimp=".95 .99 .0001" friction="0.5" condim="1"/>
          </body>
        </replicate>
      </replicate>
    </replicate>

    <light name="left" pos="0 0 1"/>
    <light name="right" pos="1 0 1"/>
  </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.

Wel2018 · 2025-03-17T07:43:28Z

Wel2018
Mar 17, 2025
Author

By the way, how to simulate the effect of water flowing into a cup in mujoco?

0 replies

quagla · 2025-03-17T09:31:15Z

quagla
Mar 17, 2025
Collaborator

Hi you can try to reduce sdf_iterations and sdf_initpoints https://mujoco.readthedocs.io/en/latest/XMLreference.html#option-sdf-iterations, it will get faster but collisions might become less accurate.

0 replies

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The SDF plugin is very slow when simulating 200 particles #2504

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Wel2018 Mar 17, 2025

Intro

My setup

My question

Minimal model and/or code that explain my question

Confirmations

Replies: 2 comments

Uh oh!

Wel2018 Mar 17, 2025 Author

Uh oh!

quagla Mar 17, 2025 Collaborator

Wel2018
Mar 17, 2025

Wel2018
Mar 17, 2025
Author

quagla
Mar 17, 2025
Collaborator