_onRendererDisposed() {
        // cancel animation frame
        this._animationFrameID && window.cancelAnimationFrame(this._animationFrameID);

        // remove event listeners
        this._resizeHandler && window.removeEventListener("resize", this._resizeHandler, false);
        this._scrollManager && this._scrollManager.dispose();
    }
This is called when the renderer has finished disposing all the WebGL stuff
*