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Can't apply convex decomposition to a hollow cylinder (STL file) in Python? #53

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kurtenkera opened this issue Aug 2, 2024 · 4 comments
Open

Can't apply convex decomposition to a hollow cylinder (STL file) in Python? #53

kurtenkera opened this issue Aug 2, 2024 · 4 comments

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@kurtenkera
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Hi,

I am trying to use the example script python/package/bin/coacd on an STL file of a hollow cylinder (attached:
hollowcyl.zip).

image

I want to decompose this cylinder into a union of convex objects so I can accurately simulate collision detection in MuJoCo. The picture above shows the hollow cylinder in a MuJoCo simulation. The video below shows that a small sphere is unable to fall through the hollow cylinder as its convex hull doesn't allow this.

Screencast.from.02-08-24.11.50.29.webm

When I execute the code:

cd python
python package/bin/coacd -i hollowcyl.stl -o hollowcyl_coacd.stl

I still get the same issues, whereas I was expecting this to produce an STL file that allows the sphere to fall through the cylinder? I have read the code in python/package/bin/coacd line-by-line and I don't know why I am encountering this issue. Can anyone help?

Thanks in advance!
@SarahWeiii
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Owner

Hi here are the .obj and .stl files that coacd generated, by visualization I feel the results are reasonble, can you show the coacd result you generate to compare? I also attached the files.

Screenshot 2024-08-01 at 23 15 33 Screenshot 2024-08-01 at 23 15 45

out.zip

@CumulusAlpha
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Hello, CoACD!
I have tried your out.zip in my mujoco, however, it doesn't work as well. You can see as below:
2025-01-12 14-07-20 的屏幕截图

And after I hold the "H" button(which can show the real convex mesh, i think), the hole is filled up again like below:
2025-01-12 14-13-50 的屏幕截图

I am wondering how can I solve this problem, thanks for your kind helping!

@CumulusAlpha
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CumulusAlpha commented Jan 12, 2025 •
edited
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And here is my mujoco code, sorry for that i forget to post it before:
`

<geom name="floor" size="0 0 0.05" type="plane" material="groundplane"/>
    
<body name="sphere1" pos="1 1 10">
  <joint type="free" name="sphere_joint" damping="0.001"/>
  <geom name="sphere1" type="sphere" size="0.1" rgba="1 1 1 1" mass="0.2"/>
</body>

<body name="cylinder1">
  <joint type="free" name="cylinder_joint" damping="0.001"/>
  <geom name="cylinder1" type="mesh" mass="1"  rgba="1 1 1 1" mesh="cylinder1"/>
</body>

`

image

@CumulusAlpha
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CumulusAlpha commented Jan 14, 2025 •
edited
Loading

Oh, i think i figure out the problem When you import the part, do not just import a single Stl file that coacd generates! Instead, let coacd generate several parts and include them in just one body.

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3 participants
@SarahWeiii @CumulusAlpha @kurtenkera