Spring/damper doing nothing for articulations

[mlp1802]

When trying to drive my articulation joints, only "max_force" affects my articulation moving speed. Spring/damper can be zero or a billion, it makes no difference. What could be wrong? Physx 5.1.3..(used from rust but that shouldn't matter)

pub fn set_articulation_joint_reduced_target(
    joint: PtrArticulationJointReducedCoordinate,
    axis: PxArticulationAxis,
    max_force: f32,
    spring: f32,
    damper: f32,
    target: f32,
) {
    unsafe {
        let drive = PS::PxArticulationDrive_new_1(
            spring,
            damper,
            max_force,
            PS::PxArticulationDriveType::Target,
        );

        PS::PxArticulationJointReducedCoordinate_setDriveParams_mut(joint, axis, &drive);
        PS::PxArticulationJointReducedCoordinate_setDriveTarget_mut(joint, axis, target, true);
        }
}

[preist-nvidia]

I am not sure - but I am sure that the drives work - please compare your setup to one of the snippets, e.g: https://github.com/NVIDIA-Omniverse/PhysX/blob/main/physx/snippets/snippetfixedtendon/SnippetFixedTendon.cpp#L126

This drive works.

[mlp1802]

Differences from my code is:

1. My code uses drive type TARGET
2. I set the drive params before every step (in the snippet it's set once)
3. Minor differences to how scene is created.
   I'll try to make a minimal example to see if I can pinpoint it further.

[preist-nvidia]

The target does nothing but hardcode to a fixed very large position gain and zero velocity gain: https://github.com/NVIDIA-Omniverse/PhysX/blob/main/physx/source/lowleveldynamics/src/DyFeatherstoneArticulation.cpp#L2644

And then set the drive to force mode. FYI we will deprecate this mode in 5.3.0.

[preist-nvidia]

Oops I see the error. Setting drive params is not allowed while the simulation is running. But I need to set spring/damper dynamically or I'm just having the same speed of animation constantly, how can that be done?

Instead of the gains, you can also set the drive target position/velocity. Here for position: https://nvidia-omniverse.github.io/PhysX/physx/5.2.1/_build/physx/latest/class_px_articulation_joint_reduced_coordinate.html?highlight=setdrivetarget#_CPPv4N36PxArticulationJointReducedCoordinate14setDriveTargetEN18PxArticulationAxis4EnumEK6PxRealb

But those are also not allowed to be set during simulation. You need to update in-between simulation steps.

[preist-nvidia]

The snippet updates the drive target, FWIW.

[mlp1802]

Yes I do update in between simulation steps..how else can you update it? Maybe during some callback or something? (I don't use any callbacks)

[mlp1802]

Ah ok so you want me to use force mode? I'm not sure, how can you drive a joint towards an orientation like that?

[mlp1802]

Instead of the gains, you can also set the drive target position/velocity. Here for position: https://nvidia-omniverse.github.io/PhysX/physx/5.2.1/_build/physx/latest/class_px_articulation_joint_reduced_coordinate.html?highlight=setdrivetarget#_CPPv4N36PxArticulationJointReducedCoordinate14setDriveTargetEN18PxArticulationAxis4En

Am I not already doing that ?
S::PxArticulationJointReducedCoordinate_setDriveTarget_mut(joint, axis, target, true);

[mlp1802]

Solved! I was under the impression that FORCE joint drive type would make the PS::PxArticulationJointReducedCoordinate_setDriveTarget_mut(joint, axis, target, true); drive towards a "FORCE" target. But now I understand that it's just a normal position.
So using the type FORCE works, spring and damper and all. Could maybe have been explained a little better in the docs, considering the complexity. But when the end is good everything is good, thanks!

[mlp1802]

Closing