Convex decomposition cause problems

Autonomous Machines Robotics - Isaac Isaac Gym
1

I am trying to use Isaac gym for a sim to real experiment however I am encountering a lot of issues. The first one would be the mesh approximation using convex decomposition for the collisions.
I am using this set of parameters and my wheels still look like they are made of legos.

        asset_options.vhacd_enabled = True
        asset_options.vhacd_params.resolution = 30000000
        asset_options.vhacd_params.max_convex_hulls = 20
        asset_options.vhacd_params.max_num_vertices_per_ch = 1
        asset_options.convex_decomposition_from_submeshes = True
        asset_options.override_inertia = False
        asset_options.override_com = False

The frustrating part is that I do not need a convex approximation at all, the wheel as described in my URDF is a perfectly convex .obj triangle mesh… Is there a way to load this mesh directly WIHTOUT PhysX ruining it? I have noticed that the FleX backend won’t do this but then I can’t use the tensor API.

I am aware of the existence of primitives such as capsules but they wont do the job.

similar problem :
https://forums.developer.nvidia.com/t/importing-to-isaacgym-breaks-collision-mesh/233357/13

2

The solution to my problem was to add the following tag :

<sdf resolution=1024/>

In the urdf file.

I came up with this by analysing the bolt and nut example, in the example you can see they are loading a very high quality collision model of the nut and bolt, check their urdf files and you’ll see this tag.

Adding this tag and removing the above code made my wheel model look way better.

Hope this helps

1 Like
3

Hello!

Were you directly loading your URDF into your scene or did you have to convert it to a USD first?

When I add the tag to my URDF file and try to convert it to a USD, it throws a “cannot parse” error. I was also under the impression that there was no way to directly load URDFs to Isaacsim.

Thanks!