Fluid inertia model

[BinglunWang]

Intro

Hi!

I am a PhD student at UCL, I use MuJoCo for my research on a swimming project.

My setup

I'm trying to use the inertia model to run simulation.

My question

Given a human character .xml, how can I modify it to have fluid forces with inertial model and with collision at same time?

Do I just set density and viscousity and then run simulation?

Or could you explain more how the swimmer example have the fluid forces in the dm_control_suite?

https://github.com/google-deepmind/dm_control/blob/main/dm_control/suite/swimmer.py
https://github.com/google-deepmind/dm_control/blob/main/dm_control/suite/swimmer.xml

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.

[yuvaltassa]

Sorry the question is unclear. Fluid forces and contacts are orthogonal.