Interface IXRGrabTransformer

An interface that allows the target position, rotation, and scale of an XRGrabInteractable to be calculated. The Process(XRGrabInteractable, XRInteractionUpdateOrder.UpdatePhase, ref Pose, ref Vector3) method is responsible for calculating the pose that the interactable will move to and the scale it will be resized to. Implementers are only responsible for calculating the pose and scale, which is handled and applied by Unity in XRGrabInteractable.

Namespace: UnityEngine.XR.Interaction.Toolkit.Transformers
Syntax
public interface IXRGrabTransformer
Remarks

Implementers are encouraged to derive from XRBaseGrabTransformer instead of this interface directly. However, advanced users can use this interface to totally override that behavior.

Properties

canProcess

Whether this grab transformer can process targets. Transformers that can process targets receive calls to Process(XRGrabInteractable, XRInteractionUpdateOrder.UpdatePhase, ref Pose, ref Vector3), transformers that cannot process do not. Transformers will still have other event methods called to allow for initialization on the frame the grab changes happens.

Declaration
bool canProcess { get; }
Property Value
Type Description
Boolean

Methods

OnGrab(XRGrabInteractable)

Called by Unity when the given Interactable is grabbed (in other words, when entering the Select state). This method won't be called again until the Interactable is released by every Interactor. Use this to do any code initialization based on the first Interactor that selects the Interactable.

Declaration
void OnGrab(XRGrabInteractable grabInteractable)
Parameters
Type Name Description
XRGrabInteractable grabInteractable

The XR Grab Interactable being grabbed.
Remarks

In other words, this will be called when the selection count changes from 0 to 1.

See Also

OnGrabCountChanged(XRGrabInteractable, Pose, Vector3)

Called by Unity each time the number of selections changes for the given Interactable while grabbed by at least one Interactor, including when it is first grabbed. Use this to do any code initialization based on each Interactor currently selecting the Interactable, for example computing the initial distance between both Interactors grabbing the object.

Declaration
void OnGrabCountChanged(XRGrabInteractable grabInteractable, Pose targetPose, Vector3 localScale)
Parameters
Type Name Description
XRGrabInteractable grabInteractable

The XR Grab Interactable being grabbed.
Pose targetPose

The current target pose for the current frame.
Vector3 localScale

The current scale of the Interactable's transform relative to the GameObjects parent.
Remarks

There will always be at least one Interactor selecting the Interactable when this method is called. In other words, this will be called when the selection count changes from 0 to 1 and whenever it subsequently changes while still above 0. This method is called by Unity right before Process(XRGrabInteractable, XRInteractionUpdateOrder.UpdatePhase, ref Pose, ref Vector3) if the selection count changed.
To get the number of Interactors selecting the Interactable in your implementation method:

grabInteractable.interactorsSelecting.Count

OnLink(XRGrabInteractable)

Called by Unity when the given Interactable links to this grab transformer. Use this to do any code initialization for the given Interactable.

Declaration
void OnLink(XRGrabInteractable grabInteractable)
Parameters
Type Name Description
XRGrabInteractable grabInteractable

The XR Grab Interactable being linked to this transformer.
See Also

OnUnlink(XRGrabInteractable)

Called by Unity when the given Interactable unlinks from this grab transformer. Use this to do any code cleanup for the given Interactable.

Declaration
void OnUnlink(XRGrabInteractable grabInteractable)
Parameters
Type Name Description
XRGrabInteractable grabInteractable

The XR Grab Interactable being unlinked from this transformer.
See Also

Process(XRGrabInteractable, XRInteractionUpdateOrder.UpdatePhase, ref Pose, ref Vector3)

Called by the linked Interactable to calculate the target pose and scale. Modify the value of targetPose and/or localScale (or neither).

Declaration
void Process(XRGrabInteractable grabInteractable, XRInteractionUpdateOrder.UpdatePhase updatePhase, ref Pose targetPose, ref Vector3 localScale)
Parameters
Type Name Description
XRGrabInteractable grabInteractable

The XR Grab Interactable to calculate the target pose and scale for.
XRInteractionUpdateOrder.UpdatePhase updatePhase

The update phase this is called during.
Pose targetPose

The target pose for the current frame.
Vector3 localScale

The scale of the Interactable's transform relative to the GameObjects parent.
Remarks

When there is more than one linked grab transformer that can process, the updated value of each ref parameter is passed to each in series according to its order in the list. You can utilize this by, for example, having the first grab transformer compute the target pose, and the second compute just the scale.
If your transformer requires the use of two or more selections, you should first check for that condition in your implementation method:

if (grabInteractable.interactorsSelecting.Count < 2) return;

See Also

See Also