[Question] Why is gravity compensation disabled in PinkInverseKinematicsAction for fixed-base articulation with gravity enabled?

[kyu-sz]

Hi all, I noticed this piece of code in PinkInverseKinematicsAction (link):

        if not self._asset.cfg.spawn.rigid_props.disable_gravity:
            # Get gravity compensation forces using cached tensor
            if self._asset.is_fixed_base:
                gravity = torch.zeros_like(
                    self._asset.root_physx_view.get_gravity_compensation_forces()[:, self._controlled_joint_ids_tensor]
                )

Seems like for fixed-base articulation with gravity enabled, it intentionally doesn't apply gravity compensation. Why?

P.S. Meanwhile I see in OmniGibson (link):

use_gravity_compensation (bool): If True, will add gravity compensation to the computed efforts. This is an experimental feature that only works on fixed base robots. We do not recommend enabling this.

[RandomOakForest]

This seems to be a design desision. For fixed-base robots with gravity enabled, the current behavior in PinkInverseKinematicsAction is essentially a conservative “do nothing” placeholder rather than a deliberate, fully justified control design choice.

[kyu-sz]

Does that mean, with gravity enabled, PinkInverseKinematicsAction only supports mobile-base robots, but doesn't support fixed-base robots? To use it for fixed-base robots, gravity must be disabled? And any reason for this design choice?