_getBackupCanvasDrawer(){
            if(!this._backupCanvasDrawer){
                this._backupCanvasDrawer = this.viewer.requestDrawer('canvas', {mainDrawer: false});
                this._backupCanvasDrawer.canvas.style.setProperty('visibility', 'hidden');
                this._backupCanvasDrawer.getSupportedDataFormats = () => this._supportedFormats;
                this._backupCanvasDrawer.getDataToDraw = this.getDataToDraw.bind(this);
            }

            return this._backupCanvasDrawer;
        }
Get the backup renderer (CanvasDrawer) to use if data cannot be used by webgl
Lazy loaded
@private
@returns {CanvasDrawer}