How do I rotate a PxD6Joint's actor globally?

Development World Creation
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1

So I am working on my custom Physics Handle, which derives from USceneComponent. I copied a lot of code from Epic’s Physics Handle.

I have developed the following functions:

void UVRPhysicsHandle::RotateGrabbedComponentToTheRight(float Degrees)
{
	if (!GrabbedComponent || FMath::IsNearlyZero(Degrees)) { return; }
	RotateGrabbedComponent(FQuat(GetUpVector(), FMath::DegreesToRadians(Degrees)));
}

void UVRPhysicsHandle::RotateGrabbedComponent(const FQuat& Rotation)
{
	if (!GrabbedComponent || !HandleData) { return; }
	
	PxTransform PoseInv = HandleData->getLocalPose(physx::PxJointActorIndex::eACTOR1).getInverse();
	PoseInv = PoseInv.transform(PxTransform(U2PQuat(Rotation)));
	HandleData->setLocalPose(physx::PxJointActorIndex::eACTOR1, PoseInv.getInverse());
    // problem: Pose is local, but Rotation is global space
}

HandleData is a physx::PxD6Joint*

The result is that the PxD6Joint rotates the GrabbedComponent (PxJointActorIndex::eACTOR1) around its origin. But the rotation should happen relative to my Physics Handle Component. If I pass in a global FQuat

RotateGrabbedComponent(FQuat(FVector(0.f, 0.f, 1.f), FMath::DegreesToRadians(Degrees)));

instead of

RotateGrabbedComponent(FQuat(GetUpVector(), FMath::DegreesToRadians(Degrees)));

The Physics Handle rotates the GrabbedComponent in the GrabbedComponent’s local space.

Any ideas?

Edit: I thought it might be worth mentioning, that getLocalPose() essentially returns a Transform from the PxActor to the Joint. In my case the Joint location is Identical to the other PxActor’s location, because the other PxActor’s local pose is the Identity Transform.

2

I solved my problem with a somewhat different approach. I feel like the basis for the original function was flawed, which made it impossible to rotate in any other way than locally.

The conversion from world space quaternion to local space quat was never really the problem. The code for that would simply be:

FQuat WorldSpaceQuat;
FQuat WorldToLocalSpaceQuat; // i.e. the global quat of the object we want to be local to. (Another world for local to is relative to)
FQuat LocalSpaceQuat = WorldToLocalSpaceQuat.Inverse() * WorldSpaceQuat;

Anyways, for anyone that’s interested, here’s my final code for the RotateGrabbedComponent method:

void UVRPhysicsHandle::RotateGrabbedComponent(const FQuat& Rotation)
{
	if (!GrabbedComponent || !HandleData) { return; }

	
	PxRigidActor* KinActor, * GrabbedActor;
	HandleData->getActors(KinActor, GrabbedActor);
	if (!KinActor || !GrabbedActor) { return; }

	PxTransform GlobalActorPose = GrabbedActor->getGlobalPose();
	PxTransform LocalActorHandlePose = HandleData->getLocalPose(physx::PxJointActorIndex::eACTOR1);
	PxTransform GlobalHandlePose = GlobalActorPose.transform(LocalActorHandlePose);
	PxTransform NewGlobalActorPose = PxTransform(GlobalActorPose.p, U2PQuat(Rotation) * GlobalActorPose.q);

	PxTransform NewLocalActorPose = NewGlobalActorPose.transformInv(GlobalHandlePose).getNormalized();
	HandleData->setLocalPose(physx::PxJointActorIndex::eACTOR1, NewLocalActorPose);
}