Kinematic Bodies in Isaac Gym

Is there an option to make a body ‘kinematic’ in Isaac Gym? I’ve tested setting the mass to zero (this is how you do it in Bullet).

I know that one option is to have the kinematic bodies be in their own collision group and then set their positions/rotations every frame to override the physics. But this still requires wasteful physics optimization. I don’t see anything immediate on the API, is there a flag somewhere I’m missing?


As you mentioned set_actor_dof_states is one way to override the physics, you can also zero the gravity or masses which might simplify the dynamic equations. Your purpose is to make the simulation faster by bypassing the physics optimization?

Yea. What I am noticing is that if I set the dof state tensor and root state tensor every frame (to make the object static), this works, but there are slight ‘jitters’ in the character. Presumably because it is still being simulated before being visualized. Is there a way to bypass the physics optimization other than what you said. I’ll try zeroing the masses.

By reducing the dt you might be able to mitigate that jittering problem. What you are looking for is kinda animation or motion study without physics simulation, from another post I noticed that we don’t have direct access to PhysX’s features in Gym environment, otherwise probably you could change some parameters and make it like a motion study. I think you have to look into PhysX or even Sim! but I’m not sure if you can do multiple simulations on GPU like Gym.