code: function _fromAngleAxis(axis, angle) {
    var s = Math.sin(angle/2);
    var c = Math.cos(angle/2);
  
    return new _Quaternion(axis.x * s, axis.y * s, axis.z * s, c);
  }
docs: Returns a quaternion for the given unit axis and angles in radians
  
  @param {Vector3} axis: unit vector
  @param {Number} angle: in radians
  @returns {Quaternion} quaternion