Proposal

Changing the "set_external_force_and_torque" method to allow applying wrenches at a position that's not the center of the articulation.

This could look like so:

    def set_external_force_and_torque(
        self,
        forces: torch.Tensor,
        torques: torch.Tensor,
        positions: torch.Tensor | None = None,
        body_ids: Sequence[int] | slice | None = None,
        env_ids: Sequence[int] | None = None,
    ):

When no positions are provided, the implementation uses the current behavior. However, if positions are provided, then it passes them to the PhysX tensor API:

self.root_physx_view.apply_forces_and_torques_at_position(
    force_data=self._external_force_b.view(-1, 3),
    torque_data=self._external_torque_b.view(-1, 3),
    position_data=self._external_wrench_positions_b.view(-1, 3),
    indices=self._ALL_INDICES,
    is_global=False,
)

Motivation

It would be great to be able to apply forces away from the center of the object. This is useful for thruster/propeller based systems such as drones, planes, boats, and satellites. In these systems, the position where the forces are applied can vary depending on the level of realism on wants to have. Also, this can be used to easily implement morphable geometries for drones, satellites, and boats, as there is no need to have different physical configurations: just to apply forces at different positions.

Alternatives

The current alternative is to create rigid bodies where you want to apply the force, but if you want to change their positions, you need to attach it to a set of joints.

Checklist

• [x ] I have checked that there is no similar issue in the repo (required)

Acceptance Criteria

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