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Modify current grabbing pose of a HandGrabInteractor dynamically

lufinkey
Level 4

I'm looking for a simple way to change the current grabbing pose of a HandGrabInteractor as it's being held (for example in response to a button press or change in the object etc). I have a dirty way of setting it using reflection but it always realigns the hand to the wrong position. Is there a correct / easier way to do this?

1 ACCEPTED SOLUTION

Accepted Solutions

lufinkey
Level 4

After spending WAY too much time trying to figure this out, I was able to get it working with the following code:

 

 

public bool ApplyNewPoseToGrabbingInteractor(HandGrabInteractor interactor, HandGrabInteractable interactableWithNewGrabPose) {
	// ensure we have a selected interactable and a valid snap address
	if (interactor.SelectedInteractable == null) {
		return false;
	}
	var snapAddress = (SnapAddress<HandGrabInteractable>)MPUtils.GetMemberValue(interactor, "_currentSnap");
	if (SnapAddress<HandGrabInteractable>.IsNullOrInvalid(snapAddress)) {
		return false;
	}
	var oldSnapPoint = snapAddress.SnapPoint;

	// get grab properties
	var hand = interactor.Hand;
	var trackedPinchPose = (Pose)MPUtils.GetMemberValue(interactor, "_trackedPinchPose");
	var trackedGripPose = (Pose)MPUtils.GetMemberValue(interactor, "_trackedGripPose");

	// get previous snap address properties
	var snappingInteractable = snapAddress.Interactable;
	var handPose = (HandPose)MPUtils.GetMemberValue(interactor, "_cachedBestHandPose");
	var snapPoint = (Pose)MPUtils.GetMemberValue(interactor, "_cachedBestSnapPoint");
	var usePinchPoint = snapAddress.SnappedToPinch;

	// update grab point values
	var grabPoint = usePinchPoint ? trackedPinchPose : trackedGripPose;
	bool poseFound = interactableWithNewGrabPose.CalculateBestPose(grabPoint, hand.Scale, hand.Handedness,
		ref handPose, ref snapPoint, out bool usesHandPose, out float poseScore);
	MPUtils.SetMemberValue(interactor, "_cachedBestHandPose", handPose);
	MPUtils.SetMemberValue(interactor, "_cachedBestSnapPoint", snapPoint);

	// apply pose if able
	if (poseFound) {
		var snapHandPose = usesHandPose ? handPose : null;
		snapAddress.Set(snappingInteractable, snapHandPose, snapPoint, usePinchPoint);
		if (interactor.SnapData != null) {
			MPUtils.SetMemberValue(interactor, "SnapData", snapAddress);
		}
		// adjust pointable element position/rotation to compensate for pose difference
		var pointableElementTransform = (snappingInteractable.PointableElement as Component)?.transform;
		var snapPointRotOffset = snapPoint.rotation * Quaternion.Inverse(oldSnapPoint.rotation);
		if (pointableElementTransform != null) {
			var oldRotation = pointableElementTransform.rotation;
			var newRotation = oldRotation * Quaternion.Inverse(snapPointRotOffset);
			pointableElementTransform.position -= -(pointableElementTransform.rotation * oldSnapPoint.position) + (newRotation * snapPoint.position);
			pointableElementTransform.rotation = newRotation;
		}
	}

	return poseFound;
}

 

 


The MPUtils.SetMemberValue and MPUtils.GetMemberValue methods are just helper methods to access private member variables via reflection.
Hopefully this saves someone else the time I spent trying to get this working! And if the oculus team reads this, it would be really awesome if you could add this as a feature! I'm sure this is probably the worst way to accomplish this

Edit: this was done on oculus interaction sdk v40, for reference

View solution in original post

1 REPLY 1

lufinkey
Level 4

After spending WAY too much time trying to figure this out, I was able to get it working with the following code:

 

 

public bool ApplyNewPoseToGrabbingInteractor(HandGrabInteractor interactor, HandGrabInteractable interactableWithNewGrabPose) {
	// ensure we have a selected interactable and a valid snap address
	if (interactor.SelectedInteractable == null) {
		return false;
	}
	var snapAddress = (SnapAddress<HandGrabInteractable>)MPUtils.GetMemberValue(interactor, "_currentSnap");
	if (SnapAddress<HandGrabInteractable>.IsNullOrInvalid(snapAddress)) {
		return false;
	}
	var oldSnapPoint = snapAddress.SnapPoint;

	// get grab properties
	var hand = interactor.Hand;
	var trackedPinchPose = (Pose)MPUtils.GetMemberValue(interactor, "_trackedPinchPose");
	var trackedGripPose = (Pose)MPUtils.GetMemberValue(interactor, "_trackedGripPose");

	// get previous snap address properties
	var snappingInteractable = snapAddress.Interactable;
	var handPose = (HandPose)MPUtils.GetMemberValue(interactor, "_cachedBestHandPose");
	var snapPoint = (Pose)MPUtils.GetMemberValue(interactor, "_cachedBestSnapPoint");
	var usePinchPoint = snapAddress.SnappedToPinch;

	// update grab point values
	var grabPoint = usePinchPoint ? trackedPinchPose : trackedGripPose;
	bool poseFound = interactableWithNewGrabPose.CalculateBestPose(grabPoint, hand.Scale, hand.Handedness,
		ref handPose, ref snapPoint, out bool usesHandPose, out float poseScore);
	MPUtils.SetMemberValue(interactor, "_cachedBestHandPose", handPose);
	MPUtils.SetMemberValue(interactor, "_cachedBestSnapPoint", snapPoint);

	// apply pose if able
	if (poseFound) {
		var snapHandPose = usesHandPose ? handPose : null;
		snapAddress.Set(snappingInteractable, snapHandPose, snapPoint, usePinchPoint);
		if (interactor.SnapData != null) {
			MPUtils.SetMemberValue(interactor, "SnapData", snapAddress);
		}
		// adjust pointable element position/rotation to compensate for pose difference
		var pointableElementTransform = (snappingInteractable.PointableElement as Component)?.transform;
		var snapPointRotOffset = snapPoint.rotation * Quaternion.Inverse(oldSnapPoint.rotation);
		if (pointableElementTransform != null) {
			var oldRotation = pointableElementTransform.rotation;
			var newRotation = oldRotation * Quaternion.Inverse(snapPointRotOffset);
			pointableElementTransform.position -= -(pointableElementTransform.rotation * oldSnapPoint.position) + (newRotation * snapPoint.position);
			pointableElementTransform.rotation = newRotation;
		}
	}

	return poseFound;
}

 

 


The MPUtils.SetMemberValue and MPUtils.GetMemberValue methods are just helper methods to access private member variables via reflection.
Hopefully this saves someone else the time I spent trying to get this working! And if the oculus team reads this, it would be really awesome if you could add this as a feature! I'm sure this is probably the worst way to accomplish this

Edit: this was done on oculus interaction sdk v40, for reference