Babylon.js/src/Cameras/Inputs/arcRotateCameraVRDeviceOrientationInput.ts

import { Nullable } from "../../types";
import { ArcRotateCamera } from "../../Cameras/arcRotateCamera";
import { ICameraInput, CameraInputTypes } from "../../Cameras/cameraInputsManager";

/**
 * Manage the device orientation inputs (gyroscope) to control an arc rotate camera.
 * @see http://doc.babylonjs.com/how_to/customizing_camera_inputs
 */
export class ArcRotateCameraVRDeviceOrientationInput implements ICameraInput<ArcRotateCamera> {
    /**
     * Defines the camera the input is attached to.
     */
    public camera: ArcRotateCamera;

    /**
     * Defines a correction factor applied on the alpha value retrieved from the orientation events.
     */
    public alphaCorrection = 1;

    /**
     * Defines a correction factor applied on the gamma value retrieved from the orientation events.
     */
    public gammaCorrection = 1;

    private _alpha = 0;
    private _gamma = 0;
    private _dirty = false;

    private _deviceOrientationHandler: () => void;

    /**
     * Instantiate a new ArcRotateCameraVRDeviceOrientationInput.
     */
    constructor() {
        this._deviceOrientationHandler = this._onOrientationEvent.bind(this);
    }

    /**
     * Attach the input controls to a specific dom element to get the input from.
     * @param element Defines the element the controls should be listened from
     * @param noPreventDefault Defines whether event caught by the controls should call preventdefault() (https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault)
     */
    public attachControl(element: HTMLElement, noPreventDefault?: boolean): void {
        this.camera.attachControl(element, noPreventDefault);
        window.addEventListener("deviceorientation", this._deviceOrientationHandler);
    }

    /** @hidden */
    public _onOrientationEvent(evt: DeviceOrientationEvent): void {
        if (evt.alpha !== null) {
            this._alpha = (+evt.alpha | 0) * this.alphaCorrection;
        }

        if (evt.gamma !== null) {
            this._gamma = (+evt.gamma | 0) * this.gammaCorrection;
        }
        this._dirty = true;
    }

    /**
     * Update the current camera state depending on the inputs that have been used this frame.
     * This is a dynamically created lambda to avoid the performance penalty of looping for inputs in the render loop.
     */
    public checkInputs(): void {
        if (this._dirty) {
            this._dirty = false;

            if (this._gamma < 0) {
                this._gamma = 180 + this._gamma;
            }

            this.camera.alpha = (-this._alpha / 180.0 * Math.PI) % Math.PI * 2;
            this.camera.beta = (this._gamma / 180.0 * Math.PI);
        }
    }

    /**
     * Detach the current controls from the specified dom element.
     * @param element Defines the element to stop listening the inputs from
     */
    public detachControl(element: Nullable<HTMLElement>): void {
        window.removeEventListener("deviceorientation", this._deviceOrientationHandler);
    }

    /**
     * Gets the class name of the current intput.
     * @returns the class name
     */
    public getClassName(): string {
        return "ArcRotateCameraVRDeviceOrientationInput";
    }

    /**
     * Get the friendly name associated with the input class.
     * @returns the input friendly name
     */
    public getSimpleName(): string {
        return "VRDeviceOrientation";
    }
}

(<any>CameraInputTypes)["ArcRotateCameraVRDeviceOrientationInput"] = ArcRotateCameraVRDeviceOrientationInput;