DeviceOrientationCameraController.js

/*global define*/
define([
        '../Core/defined',
        '../Core/destroyObject',
        '../Core/DeveloperError',
        '../Core/Math',
        '../Core/Matrix3',
        '../Core/Quaternion'
    ], function(
        defined,
        destroyObject,
        DeveloperError,
        CesiumMath,
        Matrix3,
        Quaternion) {
    'use strict';

    /**
     * @private
     */
    function DeviceOrientationCameraController(scene) {
        //>>includeStart('debug', pragmas.debug);
        if (!defined(scene)) {
            throw new DeveloperError('scene is required.');
        }
        //>>includeEnd('debug');

        this._scene = scene;

        this._lastAlpha = undefined;
        this._lastBeta = undefined;
        this._lastGamma = undefined;

        this._alpha = undefined;
        this._beta = undefined;
        this._gamma = undefined;

        var that = this;

        function callback(e) {
            var alpha = e.alpha;
            if (!defined(alpha)) {
                that._alpha = undefined;
                that._beta = undefined;
                that._gamma = undefined;
                return;
            }

            that._alpha = CesiumMath.toRadians(alpha);
            that._beta = CesiumMath.toRadians(e.beta);
            that._gamma = CesiumMath.toRadians(e.gamma);
        }

        window.addEventListener('deviceorientation', callback, false);

        this._removeListener = function() {
            window.removeEventListener('deviceorientation', callback, false);
        };
    }

    var scratchQuaternion1 = new Quaternion();
    var scratchQuaternion2 = new Quaternion();
    var scratchMatrix3 = new Matrix3();

    function rotate(camera, alpha, beta, gamma) {
        var direction = camera.direction;
        var right = camera.right;
        var up = camera.up;

        var bQuat = Quaternion.fromAxisAngle(direction, beta, scratchQuaternion2);
        var gQuat = Quaternion.fromAxisAngle(right, gamma, scratchQuaternion1);

        var rotQuat = Quaternion.multiply(gQuat, bQuat, gQuat);

        var aQuat = Quaternion.fromAxisAngle(up, alpha, scratchQuaternion2);
        Quaternion.multiply(aQuat, rotQuat, rotQuat);

        var matrix = Matrix3.fromQuaternion(rotQuat, scratchMatrix3);
        Matrix3.multiplyByVector(matrix, right, right);
        Matrix3.multiplyByVector(matrix, up, up);
        Matrix3.multiplyByVector(matrix, direction, direction);
    }

    DeviceOrientationCameraController.prototype.update = function() {
        if (!defined(this._alpha)) {
            return;
        }

        if (!defined(this._lastAlpha)) {
            this._lastAlpha = this._alpha;
            this._lastBeta = this._beta;
            this._lastGamma = this._gamma;
        }

        var a = this._lastAlpha - this._alpha;
        var b = this._lastBeta - this._beta;
        var g = this._lastGamma - this._gamma;

        rotate(this._scene.camera, -a, b, g);

        this._lastAlpha = this._alpha;
        this._lastBeta = this._beta;
        this._lastGamma = this._gamma;
    };

    /**
     * Returns true if this object was destroyed; otherwise, false.
     * <br /><br />
     *
     * @returns {Boolean} <code>true</code> if this object was destroyed; otherwise, <code>false</code>.
     */
    DeviceOrientationCameraController.prototype.isDestroyed = function() {
        return false;
    };

    /**
     * Destroys the resources held by this object.  Destroying an object allows for deterministic
     * release of resources, instead of relying on the garbage collector to destroy this object.
     * <br /><br />
     * Once an object is destroyed, it should not be used; calling any function other than
     * <code>isDestroyed</code> will result in a {@link DeveloperError} exception.  Therefore,
     * assign the return value (<code>undefined</code>) to the object as done in the example.
     *
     * @returns {undefined}
     *
     * @exception {DeveloperError} This object was destroyed, i.e., destroy() was called.
     */
    DeviceOrientationCameraController.prototype.destroy = function() {
        this._removeListener();
        return destroyObject(this);
    };

    return DeviceOrientationCameraController;
});