code: public static Vector3d getNormal(Point3d ptA, Point3d ptB, Point3d ptC) {
          Vector3d vectorAB = new Vector3d();
          Vector3d vectorAC = new Vector3d();
          Vector3d normal = new Vector3d();
          StereoTool.getRawNormal(ptA, ptB, ptC, normal, vectorAB, vectorAC);
          normal.normalize();
          return normal;
      }
docs: <p>Given three points (A, B, C), makes the vectors A-B and A-C, and makes
  the cross product of these two vectors; this has the effect of making a
  third vector at right angles to AB and AC.</p>
  
  <p>NOTE : the returned normal is normalized; that is, it has been
  divided by its length.</p>
  
  @param ptA the 'middle' point
  @param ptB one of the end points
  @param ptC one of the end points
  @return the vector at right angles to AB and AC