quaternion to matrix

qtn.js

/**
 * @class InteractionCamera
 * @example
 * let camera = new InteractionCamera();
 * window.addEventListener('mousedown', camera.startEvent, false);
 * window.addEventListener('mousemove', camera.moveEvent, false);
 * window.addEventListener('mouseup', camera.endEvent, false);
 * camera.update();
 * mMatrix = gl3.Math.Qtn.toMat4(camera.qtn, mMatrix);
 */
class InteractionCamera {
    /**
     * @constructor
     */
    constructor(){
        this.qtn               = qtn.identity(qtn.create());
        this.dragging          = false;
        this.prevMouse         = [0, 0];
        this.rotationScale     = Math.min(window.innerWidth, window.innerHeight);
        this.rotation          = 0.0;
        this.rotateAxis        = [0.0, 0.0, 0.0];
        this.rotatePower       = 1.5;
        this.rotateAttenuation = 0.9;
        this.scale             = 1.0;
        this.scalePower        = 0.0;
        this.scaleAttenuation  = 0.8;
        this.scaleMin          = 0.5;
        this.scaleMax          = 1.5;
        this.startEvent        = this.startEvent.bind(this);
        this.moveEvent         = this.moveEvent.bind(this);
        this.endEvent          = this.endEvent.bind(this);
        this.wheelEvent        = this.wheelEvent.bind(this);
    }
    /**
     * mouse down event
     * @param {Event} eve - event object
     */
    startEvent(eve){
        this.dragging = true;
        this.prevMouse = [eve.pageX, eve.pageY];
    }
    /**
     * mouse move event
     * @param {Event} eve - event object
     */
    moveEvent(eve){
        if(this.dragging !== true){return;}
        let x = this.prevMouse[0] - eve.pageX;
        let y = this.prevMouse[1] - eve.pageY;
        this.rotation = Math.sqrt(x * x + y * y) / this.rotationScale * this.rotatePower;
        this.rotateAxis[0] = y;
        this.rotateAxis[1] = x;
        this.prevMouse = [eve.pageX, eve.pageY];
    }
    /**
     * mouse up event
     */
    endEvent(){
        this.dragging = false;
    }
    /**
     * wheel event
     * @param {Event} eve - event object
     */
    wheelEvent(eve){
        let w = eve.wheelDelta;
        if(w > 0){
            this.scalePower = 0.01;
        }else if(w < 0){
            this.scalePower = -0.01;
        }
    }
    /**
     * quaternion update
     */
    update(){
        this.scalePower *= this.scaleAttenuation;
        this.scale = Math.max(this.scaleMin, Math.min(this.scaleMax, this.scale + this.scalePower));
        if(this.rotation === 0.0){return;}
        this.rotation *= this.rotateAttenuation;
        let q = qtn.identity(qtn.create());
        q = qtn.rotate(this.rotation, this.rotateAxis);
        this.qtn = qtn.multiply(this.qtn, q);
    }
}