Isaac Sim Version
5.0.0
Operating System
Ubuntu 22.04
Hello, I am trying to do the following:
I have a custom mesh that I imported using .STL/.GLB which is like a semicircle and I want to make it deformable and actuate it using cables. The way I want to do it is use deformable body API and distance joints to simulate the behaviour. However, I have an issue.
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I tried using the beta deformable body APIs but I cannot get them to work as intended. My deform body is made of TPU 95A (https://um-support-files.ultimaker.com/materials/2.85mm/tds/TPU-95A/Ultimaker-TPU95A-TDS-v5.00.pdf) and when I use deform body and get the material props to it, the deform body is not behaving the same. it is not stifff enough to maintain its original position and collapses on itself. Basically, It is acting like a jelly which it should not do. I reduced the mesh solver resolution from 10 to 4 and then it doesn’t collapse on itself but I am not sure it is the way to do it…
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assuming this way is okay, the second part I did was I needed to have rigid body attachments which I can use to actuate the deform body using the distance joints. how, but I attach the rigid bodies to the deform body using Add→Physics→Attachment, it seems it attaches but it is not properly fixed to the deform bdy and it just pulls away form it. I want the rigid bodies to be like screws. I have attached the screenshots:
In the above, u can see the deform body, (I disabled collision mesh simplification) and a cube and sphere rigid body with collider presets on it. this is before the sim starts.
The above is when I run the simulation. I do not understand by the attachment is not fully fixed. Please help.
NOTE: This is using the deformable body API (deprecated) as the beta version is not working for me)
Hi @shivengarg8426, thank you for posting your question. Regarding the stiffness of the deformable, making the mesh coarser is one way to make it stiffer but it really is more of a simulation artifact. If you make the mesh resolution higher, you will need to adjust some parameters in the Deformable material to get it to behave the way you want it. Decreasing Elastic Damping will make the object stiffer.
Also, it helps to increase simulation the Time Steps Per Second in the physics scene setting (you might need to create a physics scene if there isn’t one already). The default value is 60, but it is too coarse for fine meshes and can make deformables appear as softer.
Finally, on the issue of making the attachment “welded” unfortunately the feature is not perfect and currently it does a best attempt to make the attachment points fixed.
All in all the deprecated deformables in physX definitely has a few drawbacks. Hopefully the up and coming Newton GitHub - newton-physics/newton: An open-source, GPU-accelerated physics simulation engine built upon NVIDIA Warp, specifically targeting roboticists and simulation researchers. integration into Isaac Sim will provide a much higher fidelity deformables simulation.
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