Object floating above the ground in Isaac Sim

Good morning,

I’m creating a robotics simulation in Isaac Sim and I have a terrain with some slopes. I added the option “Rigid Body with Colliders Preset” both to the ground and the object. The result is that the object floats above the terrain when the latter goes down (decrease in the z coordinate). I attach below the picture of the behavior. Could you please tell me how to solve the problem? Thanks in advance!

Maybe you can try to change the approximation of the mesh Collider.

Select the target mesh in the stage, in property → Physics → Collider → Approximation
Usually, the “convexDecomposition” does a good job in my cases.

I tried “convexDecomposition” and it was pretty much the same as “convexHull”. After I tried “SDF Mesh” and the cube finally touched the ground, also looking at the collisions I can see that they follow the terrain. I attach a picture of that below. Thanks for the suggestion to change Approximation method!

But now I have a doubt. The terrain in the picture is just a part of a big environment where I want to simulate my robots. That environment is composed of many many pieces, I saw that selecting all the pieces in the stage is possible to add them the option “Rigid Body with Colliders Preset”. But is there a way to set “SDF Mesh” as approximation method for all the parts? Changing it manually for each object in the stage will take hours…

Hi @paros97 , does this document help? Deformable-Body Simulation — Omniverse Workflows documentation

Are your units matching the stage units (metersPerUnits), I am asking because some attributes like contactOffset is computed based on that.
Having said that, its most likely contactOffset that makes the objects settle above the ground so high. You can change the contactOffset manually by selecting the cube and in the collision API advanced section you can set some value. Note that the value needs to respect the scaling of your scene, typically for a meters scene the default is 0.02, but it really depends on your scene scale.

Hi @rthaker, thanks for the suggestion , I did not know about deformable objects in Isaac Sim. It is good to know it.

@AlesBorovicka thanks for the reply, I scaled the usd file using the “USD Unit Converter” tool and I’m quite sure that the scale is correct. As I said in the previous post the problem was solved after changing the approximation method to “SDF Mesh”. After I discovered that also “Triangle Mesh” does a good work.

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