Experiment with soft bodies - #10
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Set the Z dimension spacing to 1 for clarity Set the elasticity poisson constant to better reflect known constants for webbing.
ndunkelb-nasa
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Thanks Jodi, this is immensely helpful! It will save a ton of time and headache as more people are looking at flexible things in the future!
It does look like the pre-commit is failing. Have you run pre-commit on stuff before?
If not, I think it should be something like.
# install pre-commit. Don't do the apt version bc apparently that isn't correct.
# Don't ask me how I know...
pip install pre-commit
# run pre-commit and see any issues it has. Run this from somewhere inside the repo.
pre-commit run -a
# fix issues then commit again, and you should see the tests here pass|
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| ### *dim* | ||
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| At first I thought this shold be 3 dimensional, but there is no "flex" in the third dimension, so it wasn't necessary. |
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| At first I thought this shold be 3 dimensional, but there is no "flex" in the third dimension, so it wasn't necessary. | |
| At first I thought this should be 3 dimensional, but there is no "flex" in the third dimension, so it wasn't necessary. |
| All of these parameters came from trial and error. | ||
| As I learned more about how the flexcomps work, I was able to get the behavior I wanted, but the way I did this is not necessarily the only way -- for instance, I suspect there is a reasonable way to use a mesh type instead of a grid type and there is likely a reasonable way to model this as more explicitly 3 dimensional. | ||
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| ## *Flexcomp Attributes* |
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| ## *Flexcomp Attributes* | |
| ## *Flexcomp Attributes* | |
| The MuJoCo documentation for the flexcomp type are located [here](https://mujoco.readthedocs.io/en/3.2.6/XMLreference.html#body-flexcomp), but further explanation for this application is shown below. |
| ### *dim* | ||
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| At first I thought this shold be 3 dimensional, but there is no "flex" in the third dimension, so it wasn't necessary. | ||
| From a collision standpoint the *radius" parameter gives the strap volume. |
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| From a collision standpoint the *radius" parameter gives the strap volume. | |
| From a collision standpoint the *radius* parameter gives the strap volume. |
| ### *count*, and *spacing* | ||
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| Count and spacing determine the size of the object. | ||
| Count determines how many verticies will be in each dimension. Count*Spacing gives the length in each dimension. |
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| Count determines how many verticies will be in each dimension. Count*Spacing gives the length in each dimension. | |
| Count determines how many verticies will be in each dimension. | |
| Count*Spacing gives the length in each dimension. |
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| ### *rgba* | ||
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| Selected from the CPC baseball card. |
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| Selected from the CPC baseball card. |
| The documentation here is not clear (at least to me), but trial and error says it has to be "true". | ||
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| ### *solref* | ||
| Not set with much thought. |
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I find that the more I think about some mujoco params, the less sense they make to be fair!
| Selected from the CPC baseball card. | ||
| We should set it to whatever we want. | ||
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| ### *edge* |
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| ### *edge* | |
| ## *edge* |
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| ### *young* | ||
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| I wanted no stretch, so I set the young's constant high. |
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Just out of curiousity, did you look up any comparable numbers for this, or just trial and error? when getting into the 1.0eX, it is tough to have the intuition!
ndunkelb-nasa
approved these changes
Apr 17, 2026
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Added a mujoco model for a Crew Portable Carrier (CPC) with a flexible web handle.