code: public Quaterniond toQuaternion(double x, double y, double z) {
          return Quaterniond.fromAngleRadAxis(getAngleRad(), x, y, z);
      }
docs: Converts this complex to a quaternion by
  using the provided double components vector
  as a rotation axis.
  
  @param x The x component of the axis vector
  @param y The y component of the axis vector
  @param z The z component of the axis vector
  @return A quaternion of this rotation around the given axis