Meta Developers

Design Guideline: Providing a comfortable hand tracking experience is essential for creating immersive and enjoyable apps. Refer to the Hand Tracking Design Guide to learn about best practices and to minimize risks of user discomfort.

Distance Hand Grab lets you use your hands to grab and move objects that are out of arm’s reach. Typically, this means attracting the object toward the hand and then grabbing like you do in a hand grab interaction.

Note: If you are just getting started with this Meta XR feature, we recommend that you use Building Blocks, a Unity extension for Meta XR SDKs, to quickly add features to your project.

DistanceHandGrabInteractor

The DistanceHandGrabInteractor is the Interactor class for this interaction. Like HandGrabInteractor, it uses the HandGrabAPI, Wrist, Grip, and PinchPoints, and can align a Synthetic hand visually. However, it detects eligible interactables differently.

To detect and select the best distant interactables, DistanceHandGrabInteractor uses multiple conical frustums.

SelectionFrustum: Objects inside this frustum are checked immediately, and the most centered one will become the new selected interactable. This frustum should be set to a point relative to the wrist instead of the Pointer Pose.
Optional Deselection Frustum: When set, the Selected interactable must exit this frustum rather than the SelectionFrustum, in order to be deselected. It should be wider than the SelectionFrustum. It also allows interactables to become stickier when no better interactables are within the Selection range. This frustum should be set to a point relative to the wrist instead of the Pointer Pose.
Optional Aid Frustum: When provided, interactables must be within both the SelectionFrustum and this frustum in order to be eligible for selection. Typically, this frustum originates from the head.
- Aid Blending: This indicates how centered an interactable must be within the Selection or Aid frustums to be selected. Values range from 0 to 1. A value of 0 indicates that the interactable must be within both frustums but it will be scored as centered within the SelectionFrustum. A value of 1 indicates that it is scored better if it is more centered within the Aid Frustum (Gaze selection).
Detection Delay: This value (in seconds) indicates how long the interactable must remain the best candidate before it becomes selected. Increasing this value helps reduce the chance of a false positive in noisy environments.

As demonstrated in the DistanceGrabExamples scene, the recommended approach for configuring the frustums is to set the Selection and Deselection frustums to a point relative to the wrist (instead of the Pointer Pose). Use FilteredTransforms for the frustum origins to keep the frustums stable while allowing the wrist to turn in order to select nearby interactables.

DistanceHandGrabInteractable

The DistanceHandGrabInteractable is the Interactable class of this interaction. It uses the same fields as the HandGrabInteractable. Additionally, it will copy those fields when you add it to a GameObject that already has a configured HandGrabInteractable component attached.

The versatility of the DistanceHandGrabInteractable is provided by the Movement Provider field, which indicates how the interactable moves when selected. If no value is provided, the interactable will move toward the interactor, and then attach to it and move in sync with it. Other behaviors are also provided (and additional behaviors can be created by implementing IMovementProvider). These can be found in the Movements folder, but some of the most relevant ones include the following:

MoveTowardsTarget: Attaching this behavior as a component allows tweaking the different parameters such as easing curve or velocity. For more information, see the Interactable Movements section.
AutoMoveTowardsTarget: This behavior is similar to MoveTowardsTarget but this behavior will finish the movement toward the interactor even if the selection is interrupted. This behavior is useful for quickly attracting multiple objects toward the user.
MoveFromTarget: This behavior does not attract an object toward the interactor, but rather it anchors the object at the interactor pose, allowing the interactor to move it a distance.
MoveAtSource: This moves the interactable at its current position, but does so using the delta movement of the interactor, as if the hand jumped automatically to the interactable position and moved it from there.

Ray Visual

Often used as a ghost reticle, DistantInteractionLineVisual draws a dotted line that connects the interactor with the currently hovered interactable. It’s possible to modify the material and thickness of the line, and it uses PolylineRenderer for the visuals.

Reference

For reference information about the components used by distance hand grab, see the following links.

To learn about best practices when designing for hands, see Designing for Hands.
To try distance hand grab in a prebuilt scene, see the DistanceGrabExamples scene.
To add Distance Hand Grab Interactions, see either Add an Interaction with Quick Actions if you’re using v62+, or Create Distance Hand Grab Interactions if you’re using a legacy version.
To add visual indicators that show when you’re hovering or selecting a distant object, see Create Ghost Reticles.

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