code: public static double orientationAngle(Point3d[] fixed, Point3d[] moved) {
  		Quat4d q = relativeOrientation(fixed, moved);
  		return angle(q);
  	}
docs: The angle of the relative orientation of the two sets of points in 3D.
  Equivalent to {@link #angle(Quat4d)} of the unit quaternion obtained by
  {@link #relativeOrientation(Point3d[], Point3d[])}.
  <p>
  The arrays of points need to be centered at the origin. To center the
  points use {@link CalcPoint#center(Point3d[])}.
  
  @param fixed
  array of Point3d, centered at origin. Original coordinates
  will not be modified.
  @param moved
  array of Point3d, centered at origin. Original coordinates
  will not be modified.
  @return the angle in radians of the relative orientation of the points,
  angle to rotate moved to bring it to the same orientation as
  fixed.