Example Line Segment Intersections

The following program shows how to compute the intersections between 50 random segments. After computing the intersection, a window is used to display the segments and the intersections. On the right you see a set of 50 segments in the plane, the intesections are drawn in red. The picture is a screenshot from the program below. Remark: LEDA provides several variants for computing intersections between line segments using different algorithms and satisfying different output requirements. See the Manual Page of Geometry Algorithms and the LEDA Book for details.

#include <LEDA/core/list.h>
#include <LEDA/geo/point.h>
#include <LEDA/geo/random_point.h>
#include <LEDA/graphics/window.h>
#include <LEDA/geo/geo_alg.h>

using namespace leda;

int main()
{
  list<point> LP;
  random_points_in_square(50,100,LP);  

  list<segment> L;
  while (!LP.empty()) {
    point p=LP.pop();point q=LP.pop();
    L.append(segment(p,q));
  }

  list<point> intersections;
  SEGMENT_INTERSECTION(L,intersections);
 
  window W;
  W.init(-110,110,-110);
  W.open(); W.display();
  W.set_node_width(3);

  segment s; forall(s,L) W.draw_segment(s);
  W.read_mouse();
  point p; forall(p,intersections) W.draw_filled_node(p,red);
  W.read_mouse();
  W.screenshot("segment_intersection");

  return 0;
}	   

See also:

Data Types for 2-D Geometry

Linear Lists

Windows and Panels

Writing Kernel Independent Code

Geometry Algorithms

Geometry

GeoWin

Number Types

Manual Entries

Manual Page of Geometry Algorithms