Class ViewBox

ViewBox automatically fits a defined box area into the camera view regardless of screen size or aspect ratio.
This component is useful for framing characters, objects, or scenes in the center of the view while ensuring they remain fully visible.
You can animate or scale the viewbox to create dynamic zoom effects, cinematic transitions, or responsive framing.

The ViewBox component works by adjusting the camera's focus rect settings (offset and zoom) to ensure that the box defined by the GameObject's position, rotation, and scale fits perfectly within the visible viewport. It supports different modes for one-time fitting or continuous adjustment, making it versatile for both static compositions and animated sequences.

Key Features:

  • Automatically adjusts camera framing to fit the box area
  • Works with any screen size and aspect ratio
  • Supports one-time fitting or continuous updates
  • Can be animated for dynamic zoom and framing effects
  • Multiple ViewBoxes can be active, with the most recently enabled taking priority
  • Handles camera positioning to ensure the box is visible (moves camera if inside the box)

Common Use Cases:

Example: Basic setup - Add a ViewBox component to frame an object

const viewBox = new Object3D();
viewBox.position.set(0, 1, 0); // Position the viewbox center
viewBox.scale.set(2, 2, 2);    // Define the box size
viewBox.addComponent(ViewBox, { debug: true });
scene.add(viewBox);

Example: Animated ViewBox for zoom effects

const viewBox = new Object3D();
viewBox.addComponent(ViewBox, { mode: "continuous" });
scene.add(viewBox);

// Animate the viewbox scale over time
function update() {
  const scale = 1 + Math.sin(Date.now() * 0.001) * 0.5;
  viewBox.scale.setScalar(scale);
}

Example: One-time fitting with user control afterwards

const viewBox = new Object3D();
viewBox.addComponent(ViewBox, {
  mode: "once", // Fit once, then allow free camera control
  referenceFieldOfView: 60
});
scene.add(viewBox);

See

  • Camera - The camera component that ViewBox controls
  • OrbitControls - Camera controls that work alongside ViewBox
  • DragControls - Alternative camera controls compatible with ViewBox
  • LookAtConstraint - Another way to control camera targeting
  • SceneSwitcher - Can be combined with ViewBox for scene transitions
  • Context.setCameraFocusRect - The underlying focus rect API used by ViewBox
  • Context.focusRectSettings - Manual control of focus rect settings
  • ViewBoxMode - The mode type for controlling ViewBox behavior

Component

Hierarchy (View Summary)

Properties

debug gameObject guid referenceFieldOfView sourceId? instances

Accessors

[$componentName] activeAndEnabled context destroyed enabled forward layer mode name right scene static tag up worldEuler worldPosition worldQuaternion worldRotation

Methods

addEventListener awake destroy dispatchEvent earlyUpdate? lateUpdate? onAfterRender? onBeforeRender? onBeforeXR? onCollisionEnter? onCollisionExit? onCollisionStay? onDestroy onEnterXR? onLeaveXR? onPausedChanged? onPointerClick? onPointerDown? onPointerEnter? onPointerExit? onPointerMove? onPointerUp? onTriggerEnter? onTriggerExit? onTriggerStay? onUpdateXR? onValidate? onXRControllerAdded? onXRControllerRemoved? removeEventListener resolveGuids? setWorldPosition setWorldQuaternion setWorldRotation start? startCoroutine stopCoroutine supportsXR? update?

Properties

debug

debug: boolean = false

Enables debug visualization and logging for this ViewBox instance.

When enabled, you will see:

  • A yellow wireframe box showing the active ViewBox bounds in 3D space
  • Gray wireframe boxes for inactive ViewBox instances
  • A red dashed outline on screen showing the projected box in 2D (when using ?debugviewbox URL parameter)
  • Console logs for mode changes, FOV settings, and camera adjustments

Tip: You can also enable debug visualization globally for all ViewBoxes by adding ?debugviewbox to your URL.

See

Gizmos for the gizmo rendering system used for debug visualization

Default

false

gameObject

gameObject: GameObject

Reference to the GameObject this component is attached to This is a three.js Object3D with additional GameObject functionality

guid

guid: string = "invalid"

Unique identifier for this component instance, used for finding and tracking components

referenceFieldOfView

referenceFieldOfView: number = -1

The reference field of view (in degrees) used to calculate how the box should fit within the camera view. This determines the baseline camera FOV for fitting calculations.

Behavior:

  • If set to -1 (default), the component will automatically use the camera's FOV on the first frame
  • Should typically match your camera's FOV for predictable framing
  • Can be set to a different value to create specific framing effects

Example: If your camera has an FOV of 60° and you set referenceFieldOfView to 60, the ViewBox will fit objects as they would appear with that field of view. Setting it to a wider FOV (e.g., 90) makes objects appear smaller, while a narrower FOV (e.g., 30) makes them appear larger.

See

Camera for the camera component and its FOV property

Default

-1 (automatically uses the camera's FOV on the first frame)

OptionalsourceId

sourceId?: string

Identifier for the source asset that created this component. For example, URL to the glTF file this component was loaded from

Static Readonlyinstances

instances: ViewBox[] = []

Array of all active ViewBox instances in the scene. When multiple ViewBoxes are enabled, the last one in the array (most recently enabled) takes priority and controls the camera. Other ViewBoxes remain registered but inactive, displayed with a dimmed gizmo color when debug visualization is enabled.

Accessors

[$componentName]

  • get "[$componentName]"(): undefined | string

    Get the original component type name before minification (available if the component is registered in the TypeStore)

    Returns undefined | string

activeAndEnabled

  • get activeAndEnabled(): boolean

    Checks if this component is currently active (enabled and part of an active GameObject hierarchy) Components that are inactive won't receive lifecycle method calls

    Returns boolean

    True if the component is enabled and all parent GameObjects are active

context

  • get context(): Context

    The context this component belongs to, providing access to the runtime environment including physics, timing utilities, camera, and scene

    Returns Context

  • set context(context: Context): void

    Parameters

    Returns void

destroyed

  • get destroyed(): boolean

    Checks if this component has been destroyed

    Returns boolean

    True if the component or its GameObject has been destroyed

enabled

  • get enabled(): boolean

    Controls whether this component is enabled Disabled components don't receive lifecycle callbacks

    Returns boolean

  • set enabled(val: boolean): void

    Parameters

    • val: boolean

    Returns void

forward

  • get forward(): Vector3

    Gets the forward direction vector (0,0,-1) of this component's GameObject in world space

    Returns Vector3

layer

  • get layer(): number

    The layer value of the GameObject this component is attached to Used for visibility and physics filtering

    Returns number

mode

  • get mode(): ViewBoxMode

    Controls how the ViewBox applies camera adjustments.

    Modes:

    • "once": Applies the framing adjustment once when the ViewBox becomes active, then stops updating. This is ideal when you want to frame the view initially but allow users to freely zoom, pan, or orbit afterwards. Perfect for interactive scenes where you want a good starting view but full user control.

    • "continuous": Continuously updates the camera framing while this ViewBox is active. Use this when animating or scaling the ViewBox over time, or when you need the framing to constantly adjust. Great for cutscenes, scrollytelling, or any scenario with animated ViewBoxes.

    Example Use Cases:

    • Set to "once" for: Initial scene framing, product showcases where users explore freely after initial framing
    • Set to "continuous" for: Animated zoom effects, scrollytelling sequences, dynamic camera movements tied to ViewBox transforms

    Returns ViewBoxMode

    See

    ViewBoxMode for the type definition

    Default

    "continuous"
  • set mode(v: ViewBoxMode): void

    Parameters

    Returns void

name

  • get name(): string

    The name of the GameObject this component is attached to Used for debugging and finding objects

    Returns string

  • set name(str: string): void

    Parameters

    • str: string

    Returns void

right

  • get right(): Vector3

    Gets the right direction vector (1,0,0) of this component's GameObject in world space

    Returns Vector3

scene

  • get scene(): Scene

    Shorthand accessor for the current scene from the context

    Returns Scene

    The scene this component belongs to

static

  • get static(): boolean

    Indicates whether the GameObject is marked as static Static objects typically don't move and can be optimized by the engine

    Returns boolean

  • set static(value: boolean): void

    Parameters

    • value: boolean

    Returns void

tag

  • get tag(): string

    The tag of the GameObject this component is attached to Used for categorizing objects and efficient lookup

    Returns string

  • set tag(str: string): void

    Parameters

    • str: string

    Returns void

up

  • get up(): Vector3

    Gets the up direction vector (0,1,0) of this component's GameObject in world space

    Returns Vector3

worldEuler

  • get worldEuler(): Euler

    Gets the rotation of this component's GameObject in world space as Euler angles (in radians)

    Returns Euler

  • set worldEuler(val: Euler): void

    Sets the rotation of this component's GameObject in world space using Euler angles (in radians)

    Parameters

    • val: Euler

      The world rotation Euler angles to set

    Returns void

worldPosition

  • get worldPosition(): Vector3

    Gets the position of this component's GameObject in world space.
    Note: This is equivalent to calling this.gameObject.worldPosition

    Returns Vector3

  • set worldPosition(val: Vector3): void

    Sets the position of this component's GameObject in world space

    Parameters

    • val: Vector3

      The world position vector to set

    Returns void

worldQuaternion

  • get worldQuaternion(): Quaternion

    Gets the rotation of this component's GameObject in world space as a quaternion Note: This is equivalent to calling this.gameObject.worldQuaternion

    Returns Quaternion

  • set worldQuaternion(val: Quaternion): void

    Sets the rotation of this component's GameObject in world space using a quaternion

    Parameters

    • val: Quaternion

      The world rotation quaternion to set

    Returns void

worldRotation

  • get worldRotation(): Vector3

    Gets the rotation of this component's GameObject in world space as Euler angles (in degrees)
    Note: This is equivalent to calling this.gameObject.worldRotation

    Returns Vector3

  • set worldRotation(val: Vector3): void

    Sets the rotation of this component's GameObject in world space using Euler angles (in degrees)

    Parameters

    • val: Vector3

      The world rotation vector to set (in degrees)

    Returns void

Methods

addEventListener

  • addEventListener<T extends Event>(type: string, listener: (evt: T) => any): void

    Registers an event listener for the specified event type

    Type Parameters

    Parameters

    • type: string

      The event type to listen for

    • listener: (evt: T) => any

      The callback function to execute when the event occurs

    Returns void

awake

  • awake(): void

    Called once when the component becomes active for the first time. This is the first lifecycle callback to be invoked

    Returns void

destroy

  • destroy(): void

    Destroys this component and removes it from its GameObject After destruction, the component will no longer receive lifecycle callbacks

    Returns void

dispatchEvent

  • dispatchEvent(evt: Event): boolean

    Dispatches an event to all registered listeners

    Parameters

    • evt: Event

      The event object to dispatch

    Returns boolean

    Always returns false (standard implementation of EventTarget)

OptionalearlyUpdate

  • earlyUpdate(): void

    Called at the beginning of each frame before regular updates. Use for logic that needs to run before standard update callbacks.

    Returns void

OptionallateUpdate

  • lateUpdate(): void

    Called after all update functions have been called. Use for calculations that depend on other components being updated first.

    Returns void

OptionalonAfterRender

  • onAfterRender(): void

    Called after the scene has been rendered. Use for post-processing or UI updates that should happen after rendering

    Returns void

OptionalonBeforeRender

  • onBeforeRender(frame: null | XRFrame): void

    Called immediately before the scene is rendered.

    Parameters

    • frame: null | XRFrame

      Current XRFrame if in an XR session, null otherwise

    Returns void

OptionalonBeforeXR

  • onBeforeXR(mode: XRSessionMode, args: XRSessionInit): void

    Called before an XR session is requested Use to modify session initialization parameters

    Parameters

    • mode: XRSessionMode

      The XR session mode being requested

    • args: XRSessionInit

      The session initialization parameters that can be modified

    Returns void

OptionalonCollisionEnter

  • onCollisionEnter(col: Collision): any

    Called when this component's collider begins colliding with another collider.

    Parameters

    • col: Collision

      Information about the collision that occurred

    Returns any

OptionalonCollisionExit

  • onCollisionExit(col: Collision): any

    Called when this component's collider stops colliding with another collider.

    Parameters

    • col: Collision

      Information about the collision that ended

    Returns any

OptionalonCollisionStay

  • onCollisionStay(col: Collision): any

    Called each frame while this component's collider is colliding with another collider

    Parameters

    • col: Collision

      Information about the ongoing collision

    Returns any

onDestroy

  • onDestroy(): void

    Called when the component is destroyed. Use for cleanup operations like removing event listeners

    Returns void

OptionalonEnterXR

OptionalonLeaveXR

OptionalonPausedChanged

  • onPausedChanged(isPaused: boolean, wasPaused: boolean): void

    Called when the context's pause state changes.

    Parameters

    • isPaused: boolean

      Whether the context is currently paused

    • wasPaused: boolean

      The previous pause state

    Returns void

OptionalonPointerClick

OptionalonPointerDown

OptionalonPointerEnter

OptionalonPointerExit

OptionalonPointerMove

OptionalonPointerUp

OptionalonTriggerEnter

  • onTriggerEnter(col: ICollider): any

    Called when this component's trigger collider is entered by another collider

    Parameters

    • col: ICollider

      The collider that entered this trigger

    Returns any

OptionalonTriggerExit

  • onTriggerExit(col: ICollider): any

    Called when another collider exits this component's trigger collider

    Parameters

    • col: ICollider

      The collider that exited this trigger

    Returns any

OptionalonTriggerStay

  • onTriggerStay(col: ICollider): any

    Called each frame while another collider is inside this component's trigger collider

    Parameters

    • col: ICollider

      The collider that is inside this trigger

    Returns any

OptionalonUpdateXR

OptionalonValidate

  • onValidate(prop?: string): void

    Called when a field decorated with @validate() is modified.

    Parameters

    • Optionalprop: string

      The name of the field that was changed

    Returns void

OptionalonXRControllerAdded

OptionalonXRControllerRemoved

removeEventListener

  • removeEventListener<T extends Event>(
        type: string,
        listener: (arg: T) => any,
    ): void

    Removes a previously registered event listener

    Type Parameters

    Parameters

    • type: string

      The event type the listener was registered for

    • listener: (arg: T) => any

      The callback function to remove

    Returns void

OptionalresolveGuids

  • resolveGuids(guidsMap: GuidsMap): void

    Called when this component needs to remap guids after an instantiate operation.

    Parameters

    • guidsMap: GuidsMap

      Mapping from old guids to newly generated guids

    Returns void

setWorldPosition

  • setWorldPosition(x: number, y: number, z: number): void

    Sets the position of this component's GameObject in world space using individual coordinates

    Parameters

    • x: number

      X-coordinate in world space

    • y: number

      Y-coordinate in world space

    • z: number

      Z-coordinate in world space

    Returns void

setWorldQuaternion

  • setWorldQuaternion(x: number, y: number, z: number, w: number): void

    Sets the rotation of this component's GameObject in world space using quaternion components

    Parameters

    • x: number

      X component of the quaternion

    • y: number

      Y component of the quaternion

    • z: number

      Z component of the quaternion

    • w: number

      W component of the quaternion

    Returns void

setWorldRotation

  • setWorldRotation(x: number, y: number, z: number, degrees?: boolean): void

    Sets the rotation of this component's GameObject in world space using individual Euler angles

    Parameters

    • x: number

      X-axis rotation

    • y: number

      Y-axis rotation

    • z: number

      Z-axis rotation

    • degrees: boolean = true

      Whether the values are in degrees (true) or radians (false)

    Returns void

Optionalstart

  • start(): void

    Called once at the beginning of the first frame after the component is enabled. Use for initialization that requires other components to be awake.

    Returns void

startCoroutine

  • startCoroutine(routine: Generator, evt?: FrameEvent): Generator

    Starts a coroutine that can yield to wait for events. Coroutines allow for time-based sequencing of operations without blocking. Coroutines are based on generator functions, a JavaScript language feature.

    Parameters

    • routine: Generator

      Generator function to start

    • evt: FrameEvent = FrameEvent.Update

      Event to register the coroutine for (default: FrameEvent.Update)

    Returns Generator

    The generator function that can be used to stop the coroutine

    Example

    Time-based sequencing of operations

    *myCoroutine() {
      yield WaitForSeconds(1); // wait for 1 second
      yield WaitForFrames(10); // wait for 10 frames
      yield new Promise(resolve => setTimeout(resolve, 1000)); // wait for a promise to resolve
    }

    Example

    Coroutine that logs a message every 5 frames

    onEnable() {
      this.startCoroutine(this.myCoroutine());
    }
    private *myCoroutine() {
      while(this.activeAndEnabled) {
        console.log("Hello World", this.context.time.frame);
        // wait for 5 frames
        for(let i = 0; i < 5; i++) yield;
      }
    }

stopCoroutine

  • stopCoroutine(routine: Generator, evt?: FrameEvent): void

    Stops a coroutine that was previously started with startCoroutine

    Parameters

    • routine: Generator

      The routine to be stopped

    • evt: FrameEvent = FrameEvent.Update

      The frame event the routine was registered with

    Returns void

OptionalsupportsXR

  • supportsXR(mode: XRSessionMode): boolean

    Determines if this component supports a specific XR mode

    Parameters

    • mode: XRSessionMode

      The XR session mode to check support for

    Returns boolean

    True if the component supports the specified mode

Optionalupdate

  • update(): void

    Called once per frame during the main update loop. The primary location for frame-based game logic.

    Returns void

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