lib/Mi manual de algoritmos/version_world_finals_2009/src/geometria/distance_point_to_segment.cpp

   1 /*
   2   Returns the closest distance between point pnt and the segment
   3   that goes from point a to b
   4   Idea by:
   5   http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/
   6  */
   7 double distance_point_to_segment(const point &a,const point &b,
   8                                  const point &pnt){
   9   double u =
  10     ((pnt.x - a.x)*(b.x - a.x) + (pnt.y - a.y)*(b.y - a.y))
  11     /distsqr(a, b);
  12   point intersection;
  13   intersection.x = a.x + u*(b.x - a.x);
  14   intersection.y = a.y + u*(b.y - a.y);
  15   if (u < 0.0 || u > 1.0){
  16     return min(dist(a, pnt), dist(b, pnt));
  17   }
  18   return dist(pnt, intersection);
  19 }