Engine API Reference - v2.21.0-beta.4
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    Class XrTrackedImage

    The tracked image interface that is created by the Image Tracking system and is provided as a list from XrImageTracking#images. It contains information about the tracking state as well as the position and rotation of the tracked image.

    Hierarchy (View Summary)

    Index

    Accessors

    emulated image trackable tracking width

    Methods

    fire getPosition getRotation hasEvent off on once

    Events

    EVENT_TRACKED EVENT_UNTRACKED

    Accessors

    • get emulated(): boolean

      True if image was recently tracked but currently is not actively tracked due to inability of identifying the image by the underlying AR system. Position and rotation will be based on the previously known transformation assuming the tracked image has not moved.

      Returns boolean

    • get trackable(): boolean

      True if image is trackable. A too small resolution or invalid images can be untrackable by the underlying AR system.

      Returns boolean

    • get tracking(): boolean

      True if image is in tracking state and being tracked in real world by the underlying AR system.

      Returns boolean

    • get width(): number

      Get the width (in meters) of image in real world.

      Returns number

    • set width(value: number): void

      Width that is provided to assist tracking performance. This property can be updated only when the AR session is not running.

      Parameters

      • value: number

      Returns void

    Methods

    • Fire an event, all additional arguments are passed on to the event listener.

      Parameters

      • name: string

        Name of event to fire.

      • Optionalarg1: any

        First argument that is passed to the event handler.

      • Optionalarg2: any

        Second argument that is passed to the event handler.

      • Optionalarg3: any

        Third argument that is passed to the event handler.

      • Optionalarg4: any

        Fourth argument that is passed to the event handler.

      • Optionalarg5: any

        Fifth argument that is passed to the event handler.

      • Optionalarg6: any

        Sixth argument that is passed to the event handler.

      • Optionalarg7: any

        Seventh argument that is passed to the event handler.

      • Optionalarg8: any

        Eighth argument that is passed to the event handler.

      Returns EventHandler

      Self for chaining.

      obj.fire('test', 'This is the message');

    • Get the world position of the tracked image.

      Returns Vec3

      Position in world space.

      // update entity position to match tracked image position
      entity.setPosition(trackedImage.getPosition());

    • Get the world rotation of the tracked image.

      Returns Quat

      Rotation in world space.

      // update entity rotation to match tracked image rotation
      entity.setRotation(trackedImage.getRotation());

    • Test if there are any handlers bound to an event name.

      Parameters

      • name: string

        The name of the event to test.

      Returns boolean

      True if the object has handlers bound to the specified event name.

      obj.on('test', () => {}); // bind an event to 'test'
      obj.hasEvent('test'); // returns true
      obj.hasEvent('hello'); // returns false

    • Detach an event handler from an event. If callback is not provided then all callbacks are unbound from the event, if scope is not provided then all events with the callback will be unbound.

      Use this form to remove all listeners matching a name (and optionally callback/scope). To remove a single known subscription, prefer retaining the EventHandle returned by EventHandler#on / EventHandler#once and calling its EventHandle#off: it removes exactly that subscription and is faster (no scan of the callback list).

      Parameters

      • Optionalname: string

        Name of the event to unbind.

      • Optionalcallback: HandleEventCallback

        Function to be unbound.

      • Optionalscope: any

        Scope that was used as the this when the event is fired.

      Returns EventHandler

      Self for chaining.

      const handler = () => {};
      obj.on('test', handler);

      obj.off(); // Removes all events
      obj.off('test'); // Removes all events called 'test'
      obj.off('test', handler); // Removes all handler functions, called 'test'
      obj.off('test', handler, this); // Removes all handler functions, called 'test' with scope this

    • Attach an event handler to an event.

      Parameters

      • name: string

        Name of the event to bind the callback to.

      • callback: HandleEventCallback

        Function that is called when event is fired. Note the callback is limited to 8 arguments.

      • Optionalscope: any = ...

        Object to use as 'this' when the event is fired, defaults to current this.

      Returns EventHandle

      An event handle. For later removal, prefer retaining this handle and calling its EventHandle#off over EventHandler#off with a name/callback: it removes exactly this subscription and is faster (no scan of the callback list).

      obj.on('test', (a, b) => {
          console.log(a + b);
      });
      obj.fire('test', 1, 2); // prints 3 to the console

      // preferred removal: retain the handle and call off() on it
      const evt = obj.on('test', (a, b) => {
          console.log(a + b);
      });
      // some time later
      evt.off();

    • Attach an event handler to an event. This handler will be removed after being fired once.

      Parameters

      • name: string

        Name of the event to bind the callback to.

      • callback: HandleEventCallback

        Function that is called when event is fired. Note the callback is limited to 8 arguments.

      • Optionalscope: any = ...

        Object to use as 'this' when the event is fired, defaults to current this.

      Returns EventHandle

      An event handle. For removal before it fires, prefer retaining this handle and calling its EventHandle#off over EventHandler#off with a name/callback: it removes exactly this subscription and is faster (no scan of the callback list).

      obj.once('test', (a, b) => {
          console.log(a + b);
      });
      obj.fire('test', 1, 2); // prints 3 to the console
      obj.fire('test', 1, 2); // not going to get handled

    Events

    EVENT_TRACKED: string = 'tracked'

    Fired when image becomes actively tracked.

    trackedImage.on('tracked', () => {
        console.log('Image is now tracked');
    });
    EVENT_UNTRACKED: string = 'untracked'

    Fired when image is no longer actively tracked.

    trackedImage.on('untracked', () => {
        console.log('Image is no longer tracked');
    });

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