How to represent geometry correctly

[lyd405121]

Intro

Hi!

I am an graphic engineer, I use MuJoCo for developing an Embedded AI simulator.

My setup

Latest Mujoco 3.2.6
using pure C++
windows 10

My question

Background

• Using mujoco to pick & place basic geometry or the combination of them is tested for my case
• Which is deployed in our factory for cmos sensor pick and scan.
  
• Then my ambition turns to coffee shop for picking paper coffee cup which is treated as rigidbody while it is not
• Unfortunately, it failed。
  
• Because I use mesh type for geometry collision test, the same mesh for rendering， which is easy but not work

 <geom mesh="coffee_cup0" material="coffee_cup0" class="coffee_cup0_visual"/>
 <geom name="coffee_cup0_collision1" class="coffee_cup0_collision" type="mesh" mesh="coffee_cup0"/>

• Then I change the collision type to cylinder which is not as accurate as the reality
• But works!

<geom mesh="coffee_cup0" material="coffee_cup0" class="coffee_cup0_visual"/>
<geom name="coffee_cup0_collision1" class="coffee_cup0_collision" type="cylinder" size="0.035 0.07" pos="0.0 0.07 0.0" quat="1 1 0 0"/>

How to balance

• If I want both accurate and bettter friction to simulate collision for frustum of a cone
• There are three ways after racking my brains:
• ① fisrt，make many small cylinder to represent frustum of a cone which is like the process of differential
• ② second，generate sdf for a frustum of cone ，and using the extension of mujoco，which need lots of work to develop
• ③ third，modify the basic geometry for mujoco，make my own version of frustum of cone collision test
• Or there is a method for frition setting that out of my knowledge
• ** Really Need Help**, cause there are too many geometry shape in our world to conclude into basic shape of mujoco

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.