isVisible(obj, floating = obj.floating) {
		if (floating === true || obj.floating === true) {
			// check against screen coordinates
			return renderer.overlaps(obj.getBounds());
		} else {
			// check if within the current camera
			return obj.getBounds().overlaps(this);
		}
	}
check if the specified renderable is in the camera
@param {Renderable|Entity|Sprite|NineSliceSprite} obj - to be checked against
@param {boolean} [floating = obj.floating] - if visibility check should be done against screen coordinates
@returns {boolean} true if within the viewport