Class XrAnchor

An anchor keeps track of a position and rotation that is fixed relative to the real world. This allows the application to adjust the location of virtual objects placed in the scene in a way that helps with maintaining the illusion that the placed objects are really present in the user's environment.

Hierarchy (View Summary)

Accessors

persistent uuid

Methods

destroy fire forget getPosition getRotation hasEvent off on once persist

Events

EVENT_CHANGE EVENT_DESTROY EVENT_FORGET EVENT_PERSIST

Accessors

persistent

uuid

Methods

destroy

fire

  • fire(
        name: string,
        arg1?: any,
        arg2?: any,
        arg3?: any,
        arg4?: any,
        arg5?: any,
        arg6?: any,
        arg7?: any,
        arg8?: any,
    ): EventHandler

  • 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.

    Example

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

forget

  • forget(callback?: XrAnchorForgetCallback): void

  • Removes the persistent UUID of an anchor from the underlying system. This effectively makes the anchor non-persistent, so it will not be restored in future WebXR sessions.

    Parameters

    • Optionalcallback: XrAnchorForgetCallback

      Optional callback function to be called when the anchor has been forgotten or if an error occurs.

    Returns void

    Example

    // Forget the anchor and log the result or error
    anchor.forget((err) => {
        if (err) {
            console.error('Failed to forget anchor:', err);
        } else {
            console.log('Anchor has been forgotten');
        }
    });

getPosition

getRotation

hasEvent

  • hasEvent(name: string): boolean

  • 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.

    Example

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

off

  • off(name?: string, callback?: HandleEventCallback, scope?: object): EventHandler

  • 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: object

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

    Returns EventHandler

    Self for chaining.

    Example

    const handler = function () {
    };
    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

on

  • on(name: string, callback: HandleEventCallback, scope?: object): EventHandle

  • 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: object = ...

      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.

    Example

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

    Example

    const evt = obj.on('test', function (a, b) {
        console.log(a + b);
    });
    // some time later
    evt.off();

once

  • once(name: string, callback: HandleEventCallback, scope?: object): EventHandle

  • 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: object = ...

      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.

    Example

    obj.once('test', function (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

persist

  • persist(callback?: XrAnchorPersistCallback): void

  • Persists the anchor between WebXR sessions by generating a universally unique identifier (UUID) for the anchor. This UUID can be used later to restore the anchor from the underlying system. Note that the underlying system may have a limit on the number of anchors that can be persisted per origin.

    Parameters

    • Optionalcallback: XrAnchorPersistCallback

      Optional callback function to be called when the persistent UUID has been generated or if an error occurs.

    Returns void

    Example

    // Persist the anchor and log the UUID or error
    anchor.persist((err, uuid) => {
        if (err) {
            console.error('Failed to persist anchor:', err);
        } else {
            console.log('Anchor persisted with UUID:', uuid);
        }
    });

Events

StaticEVENT_CHANGE

EVENT_CHANGE: string = 'change'

Fired when an anchor's position and/or rotation is changed.

Example

anchor.on('change', () => {
    // anchor has been updated
    entity.setPosition(anchor.getPosition());
    entity.setRotation(anchor.getRotation());
});

StaticEVENT_DESTROY

EVENT_DESTROY: string = 'destroy'

Fired when an anchor is destroyed.

Example

// once anchor is destroyed
anchor.once('destroy', () => {
    // destroy its related entity
    entity.destroy();
});

StaticEVENT_FORGET

EVENT_FORGET: string = 'forget'

Fired when an anchor has been forgotten.

Example

anchor.on('forget', () => {
    // anchor has been forgotten
});

StaticEVENT_PERSIST

EVENT_PERSIST: string = 'persist'

Fired when an anchor has has been persisted. The handler is passed the UUID string that can be used to restore this anchor.

Example

anchor.on('persist', (uuid) => {
    // anchor has been persisted
});

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