Mastering XR Interactions: Select, Activate, Hover in Unity

In Extended Reality (XR), intuitive and responsive interactions are paramount to creating immersive and engaging user experiences. This module delves into the core interaction patterns of 'Select', 'Activate', and 'Hover' within the Unity XR Interaction Toolkit, providing the foundational knowledge for building effective AR and VR applications.

Understanding Core Interaction States

The Unity XR Interaction Toolkit defines several key states that an interactable object can be in when a user is interacting with it. We will focus on three fundamental states: Hover, Select, and Activate.

Hover: The initial point of contact.

Hover occurs when a user's pointing raycast (from a controller or gaze) enters the collider of an interactable object. It's the first signal that an object is being targeted.

The 'Hover' state is typically used to provide visual feedback to the user, indicating that an object is currently being targeted or is capable of interaction. This feedback can include highlighting the object, displaying a tooltip, or changing its appearance. In Unity XR Interaction Toolkit, this is managed by the IXRHoverInteractor interface.

What is the primary purpose of the 'Hover' interaction state in XR?

To provide visual feedback to the user, indicating that an object is currently being targeted or is capable of interaction.

Select: Grasping or picking up an object.

Select is triggered when the user performs a specific input action (like pressing a button) while hovering over an object. It signifies the user's intent to 'grab' or 'pick up' the object.

The 'Select' state is crucial for actions like picking up objects, toggling switches, or initiating a drag operation. It's a more deliberate action than hovering. The XR Interaction Toolkit uses the IXRSelectInteractor interface to manage this state. When an object is selected, it often becomes 'attached' to the interactor, moving with it.

What input action typically triggers the 'Select' interaction state?

A specific input action, such as pressing a controller button, while hovering over an object.

Activate: Performing an action on an object.

Activate is triggered by a secondary input action (often a different button press or a gesture) while an object is already selected. It's used for actions like firing a weapon, pressing a button, or confirming a choice.

The 'Activate' state represents the final confirmation of an action on an already selected object. For example, if you select a virtual button, activating it might trigger an event. This is handled by the IXRActivateInteractor interface. It allows for a two-step interaction process: first select, then activate.

What is the purpose of the 'Activate' interaction state?

To perform a secondary action or confirm a choice on an object that has already been selected.

Implementing Interactions in Unity

The Unity XR Interaction Toolkit provides components and interfaces to easily implement these interaction patterns. Key components include

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XRGrabInteractable

for objects that can be picked up, and

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XRBaseInteractable

as a base for custom interactable objects. Interactors, such as

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XRRayInteractor

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XRDirectInteractor

, are responsible for initiating these states.

Visualizing the interaction flow: A user's controller (Interactor) emits a ray. When this ray enters an object's collider, the 'Hover' state is triggered, often causing visual feedback. If the user then presses a button (Select Input), the object enters the 'Select' state, potentially attaching to the controller. A subsequent button press (Activate Input) triggers the 'Activate' state, performing an action on the object.

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Text-based content

Library pages focus on text content

Interaction State	Trigger Condition	Typical Use Case	Associated Interface
Hover	Raycast enters collider	Visual feedback, targeting	IXRHoverInteractor
Select	Hover + Select Input	Picking up, grabbing, initiating drag	IXRSelectInteractor
Activate	Select + Activate Input	Performing action, confirming choice	IXRActivateInteractor

Remember that the specific input bindings for Select and Activate are configurable within your Unity Input System setup, allowing you to map them to different controller buttons or gestures.

Customizing Interaction Behavior

You can extend the behavior of these interactions by subscribing to events on interactable objects, such as

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hoverEntered

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hoverExited

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selectEntered

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selectExited

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activated

, and

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deactivated

. This allows for dynamic responses to user actions, creating more sophisticated and engaging XR experiences.

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Learning Resources

Unity XR Interaction Toolkit Documentation(documentation)

The official Unity documentation providing a comprehensive overview of the XR Interaction Toolkit, including core concepts and components.

XR Interaction Toolkit: Interactors(documentation)

Detailed explanation of different interactor types (Ray, Direct, etc.) and how they facilitate interactions in XR.

XR Interaction Toolkit: Interactables(documentation)

Learn about the various interactable components and how to make objects interactive in your XR scenes.

Unity Learn: XR Interaction Toolkit Basics(tutorial)

A beginner-friendly learning path covering the fundamentals of setting up and using the XR Interaction Toolkit.

Creating Interactive Objects in Unity XR(video)

A practical video tutorial demonstrating how to create and configure interactive objects using the XR Interaction Toolkit.

Unity XR Interaction Toolkit: Grab and Release(video)

Focuses on the common 'grab and release' interaction pattern, explaining the underlying mechanics.

Unity XR Interaction Toolkit: Hover and Selection(video)

A tutorial specifically detailing how to implement hover and selection feedback for interactive elements.

Understanding XR Input and Interaction(blog)

An article explaining how the XR Interaction Toolkit integrates with Unity's Input System for flexible control mapping.

Best Practices for XR Interaction Design(blog)

Insights into designing intuitive and effective interactions for VR and AR experiences, applicable to Unity development.

XR Interaction Toolkit: Custom Interactables(documentation)

Guide on creating your own custom interactable components by extending the base classes provided by the toolkit.

Handling Interactions: Select, Activate, Hover

Mastering XR Interactions: Select, Activate, Hover in Unity

Understanding Core Interaction States

Hover: The initial point of contact.

Select: Grasping or picking up an object.

Activate: Performing an action on an object.

Implementing Interactions in Unity

Customizing Interaction Behavior

Learning Resources