How Can I Make A Textured Skin For Deformables

[lyd405121]

Intro

Hi! I am now developing a tool that can tranform any 3d model into a mjcf softbody automaticlly

My setup

Lastest Verison Between Mujoco 3.2.7 and 3.2.8

My question

Main Question

• I failed to make texured softbody in mujoco
• I read the mjcf spec, and found there is a chapter for object
• I have successfully make an un-skinned softbody by using , which can't be textured
• I have also successfully make a un-skinned by using in , but still don't konw how to add a textured skin
• Searching all the models in mujoco and mujoco_menagerie, dm_control,mujoco-mpc, I only found some xml with binary file called *.skn
• Is there any ascii format skin in mjcf that I can reference to

More Question

• I found there is an update for fast deformable object method.
• And I have tried the new models in the directory in "model/flex"
• But they are not able to support textured material expcept the softbox.xml which is a typed box
• Is it possible to support any textured model with this new fast deformable method.

Minimal model and/or code that explain my question

My work

• I designed a tool to make softbody with following steps
• First using fTetWild to tetrahedralize 3D model and output a .msh(gmsh file)
• Second parsing .msh and get all the points and tetrahedron index
• Third make a xml node called , building the child node with element and body attribute
• Forth filling worldbody node with points in the second step as the attribute in body node

• It was automaticlly generated by my tool from a mesh of a coffee cup
  

• Then I will make a skin using a distance analyzor for weights and morph compute(Work in progress)

• But I am stuck by the texture part. I can't find any acsii reference for textured skin in mjcf

My goal

• Make a tool for anyone using mujoco to quickly produce softbody with a singgle commond line
• If I succeed, I will open source that for everyone.
• And here's my standalone mjcf file

autogen-softbody.zip

Confirmations

• I searched the latest documentation thoroughly before posting.
• I searched previous Issues and Discussions, I am certain this has not been raised before.

[quagla]

Hi is this example useful? https://github.com/google-deepmind/mujoco/blob/main/model/flex/softbox.xml

[lyd405121]

• I have read the softbox.xml， But it is a box with builtin type <type="box">
• What I want to achieve is any 3d model skin, For example the bunny with texture

[lyd405121]

Solved By Latest Fix

• Hi，@quagla , I noticed there is a update for texutre fix
• So I try it by using fast softbody, It works!!!!
• Now the bunny has its own color

How to Make Flex textured

• First, you should have a model with uv coordinate， in *.obj file, you must find vt word inside
• Second, unlike "body" node. "flexcomp" should directly write the mesh file path

  <flexcomp type="mesh" file="bunny_with_uv.obj" pos="0 0 .1" dim="2" euler="90 0 0"
              radius=".001" material="matsponge" mass=".05" name="softbody" dof="trilinear">

• It would be nice if mujoco support xml like this:

  <asset>
    <texture name="texsponge" type="2d" file="sponge.png"/>
    <material name="matsponge" texture="texsponge" specular="0.3"/>
    <mesh name="bunny" file="bunny_with_uv.obj" scale="1 1 1"/>
  </asset>

    <flexcomp type="mesh" mesh="bunny" pos="0 0 .1" dim="2" euler="90 0 0"
              radius=".001" material="matsponge" mass=".05" name="softbody" dof="trilinear"/>

• Because in this way, we can refer to the same asset anywhere

Can I contribute my model to mujoco?

• I use UVAtlas to unwrap the original bunny.obj and name it bunny_with_uv.obj
• Then I wrote a textured bunny for softbody simulation called bunny_with_uv.xml

<mujoco model="Trilinear">
  <include file="scene.xml"/>

  <option solver="CG" tolerance="1e-6" timestep=".001" integrator="implicitfast"/>

  <size memory="100M"/>

  <visual>
    <map stiffness="100"/>
  </visual>


  <asset>
    <texture name="texsponge" type="2d" file="sponge.png"/>
    <material name="matsponge" texture="texsponge" specular="0.3"/>
  </asset>
  
  <worldbody>
    <body>
      <joint name="press" type="slide" axis="0 0 1" damping="500"/>
      <geom type="box" size=".02 .2 .2" pos="0 0 .5"/>
    </body>
    <flexcomp type="mesh" file="bunny_with_uv.obj" pos="0 0 .1" dim="2" euler="90 0 0"
              radius=".001" material="matsponge" mass=".05" name="softbody" dof="trilinear">
      <elasticity young="1e3" poisson="0.1" damping="0.001"/>
      <contact selfcollide="none" internal="false"/>
    </flexcomp>
  </worldbody>

  <actuator>
    <position name="press" joint="press" gear="-1 0 0 0 0 0" ctrlrange="-1 1" kp="1000"/>
  </actuator>
</mujoco>

• Can I contribute my model and mjcf , because I have bother the mujoco team a lot, and I also want to make a contribution to this work