docs: function _getAngleAxis(quaternion) {
    return function() {
      var sqrt = Math.sqrt(1 - quaternion.w * quaternion.w);
      return {
        axis: new Vector3(quaternion.x / sqrt, quaternion.y / sqrt, quaternion.z / sqrt),
        angle: 2 * Math.acos(quaternion.w) * radToDeg
      };
    }
  }