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With the exception of snap interactions, most of the interactions managed by the Interaction SDK follow a unified Pointer Lifecycle contract. The contract defines states for interactions and the order in which they can be traversed. This unified contract enables Pointer handlers to work with multiple interaction types without being coupled to specific implementations.

For example, a Grabbable is a Pointer handler. It consumes a set of Pointer updates from an Interactable and produces a transformation change on an object. Because Ray, Poke, and Grab interactions all adhere to the Pointer Lifecycle contract, Grabbable can work with any of them.

To learn how to use Pointer Events to send and receive information, see Use Data.

Pointer Event

The Pointer Lifecycle is fulfilled by a set of Pointer Event objects. Despite their name, Pointer Event objects aren’t events. Instead, they are payloads that represent the result of an interaction. Think of them as 3D versions of the 2D PointerEvents used in web development. Each Pointer Event object consists of four things.

Note: Snap interaction doesn’t use Pointer Events, so to learn which interactor triggered a snap interaction, check the snap interactable’s SelectingInteractorViews field. That field lists all of the interactors that are currently snapped to the interactable.

Identifier: A unique string that tells you which interactor in the scene triggered the interaction.
PointerEventType: One of the following types of events: Hover, Unhover, Select, Unselect, Move, and Cancel.
Pose: A Pose that provides the 3D coordinates of the interaction point (ex. the grab point on an object or the poke point on a surface).
Data: By default, this points to the interactor, but you can provide an object instead to pass custom data.

The output of a Pointer Event looks like this.

// Identifier
1954361006

// PointerEventType
Select

// Pose
((-0.18, 0.89, 0.37), (0.00000, 0.96593, 0.25882, 0.00000))

// Data
(-0.16, 0.88, 0.37) (0.23, 0.82, 0.34)(0.00, 0.50, -0.87) 0.005 (0.23, 0.87, 0.26) True False False True False 3 Hover

Pointer Lifecycle

An IPointable broadcasts a set of Pointer Events every time it changes state. An IPointable must adhere to the Pointer Lifecycle contract. This contract defines the order of events the IPointable can broadcast in order to transition a Pointer through three conceptual states. For more details, see Pointable.

None <-> Hovering <-> Selecting

Any Pointer must start with a Hover event (transitioning from None to Hovering).
Any Pointer must end with an Unhover event (transitions to None).
A Select event transitions a Hovering Pointer to a Selecting state.
While Selecting, no Select or Unhover events may occur.
From a Selecting state, an Unselect must occur to transition back to a Hovering state.
Any number of Move events can occur during Hovering or Selecting states.
A Cancel event may occur once during Hovering or Selecting states. If in a Selecting state, it must be followed by an Unselect and then it must then be followed by an Unhover.

Debugging Pointers

Using Interaction SDK, you can visualize what Pointer events are being produced in 3D space. Use PointableDebugGizmos to render spheres for each Pointer produced by an IPointable, including the interactables that implement IPointable, such as RayInteractable, PokeInteractable, GrabInteractable, and others.

To learn how to send and receive information via PointerEvents, see Use Data.
To learn about Pointables, which are Interactables that broadcast Pointer Events, see Pointable.

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