update() {

		this.frameId ++;

		if ( this.lastTime === undefined ) this.lastTime = performance.now();

		this.deltaTime = ( performance.now() - this.lastTime ) / 1000;

		this.lastTime = performance.now();

		this.time += this.deltaTime;

	}
Updates the internal state of the node frame. This method is
called by the renderer in its internal animation loop.