Engine API Reference - v2.7.1
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    Class XrAnchors

    Anchors provide an ability to specify a point in the world that needs to be updated to correctly reflect the evolving understanding of the world by the underlying AR system, such that the anchor remains aligned with the same place in the physical world. Anchors tend to persist better relative to the real world, especially during a longer session with lots of movement.

    app.xr.start(camera, pc.XRTYPE_AR, pc.XRSPACE_LOCALFLOOR, {
        anchors: true
    });

    Hierarchy (View Summary)

    Index

    Accessors

    available list persistence supported uuids

    Methods

    create fire forget hasEvent off on once restore

    Events

    EVENT_ADD EVENT_AVAILABLE EVENT_DESTROY EVENT_ERROR EVENT_UNAVAILABLE

    Accessors

    • get available(): boolean

      True if Anchors are available. This information is available only when session has started.

      Returns boolean

    • get uuids(): null | string[]

      Array of UUID strings of persistent anchors, or null if not available.

      Returns null | string[]

    Methods

    • Create an anchor using position and rotation, or from hit test result.

      Parameters

      • position: XRHitTestResult | Vec3

        Position for an anchor or a hit test result.

      • Optionalrotation: Quat | XrAnchorCreateCallback

        Rotation for an anchor or a callback if creating from a hit test result.

      • Optionalcallback: XrAnchorCreateCallback

        Callback to fire when anchor was created or failed to be created.

      Returns void

      // create an anchor using a position and rotation
      app.xr.anchors.create(position, rotation, (err, anchor) => {
          if (!err) {
              // new anchor has been created
          }
      });

      // create an anchor from a hit test result
      hitTestSource.on('result', (position, rotation, inputSource, hitTestResult) => {
          app.xr.anchors.create(hitTestResult, function (err, anchor) {
              if (!err) {
                  // new anchor has been created
              }
          });
      });

    • 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');

    • Forget an anchor by removing its UUID from underlying systems.

      Parameters

      • uuid: string

        UUID string associated with persistent anchor.

      • Optionalcallback: XrAnchorForgetCallback

        Callback to fire when anchor persistent data was removed or error if failed.

      Returns void

      // forget all available anchors
      const uuids = app.xr.anchors.uuids;
      for (let i = 0; i < uuids.length; i++) {
          app.xr.anchors.forget(uuids[i]);
      }

    • 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.

      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

      Can be used for removing event in the future.

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

      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

      • can be used for removing event in the future.
      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

    • Restore anchor using persistent UUID.

      Parameters

      • uuid: string

        UUID string associated with persistent anchor.

      • Optionalcallback: XrAnchorCreateCallback

        Callback to fire when anchor was created or failed to be created.

      Returns void

      // restore an anchor using uuid string
      app.xr.anchors.restore(uuid, function (err, anchor) {
          if (!err) {
              // new anchor has been created
          }
      });

      // restore all available persistent anchors
      const uuids = app.xr.anchors.uuids;
      for(let i = 0; i < uuids.length; i++) {
          app.xr.anchors.restore(uuids[i]);
      }

    Events

    EVENT_ADD: string = 'add'

    Fired when a new XrAnchor is added. The handler is passed the XrAnchor that was added.

    app.xr.anchors.on('add', (anchor) => {
        console.log('Anchor added');
    });
    EVENT_AVAILABLE: string = 'available'

    Fired when anchors become available.

    app.xr.anchors.on('available', () => {
        console.log('Anchors are available');
    });
    EVENT_DESTROY: string = 'destroy'

    Fired when an XrAnchor is destroyed. The handler is passed the XrAnchor that was destroyed.

    app.xr.anchors.on('destroy', (anchor) => {
        console.log('Anchor destroyed');
    });
    EVENT_ERROR: string = 'error'

    Fired when an anchor failed to be created. The handler is passed an Error object.

    app.xr.anchors.on('error', (err) => {
        console.error(err.message);
    });
    EVENT_UNAVAILABLE: string = 'unavailable'

    Fired when anchors become unavailable.

    app.xr.anchors.on('unavailable', () => {
        console.log('Anchors are unavailable');
    });

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