code: private static double[] toVector(Point3d src, Point3d dest) {
          return new double[]{dest.x - src.x, dest.y - src.y, dest.z - src.z};
      }
docs: Create a vector by specifying the source and destination coordinates.
  
  @param src  start point of the vector
  @param dest end point of the vector
  @return a new vector