CGAL users discussion list

[Stefan Salewski <>]

I have a minimal test program for generating the convex hull of circles
inserted into the Apollonius graph, see below. Seems to work fine.
Before I write some bindings for Ruby language, one more question: It is
possible to associate some data to each site? For the Delaunay
triangulation there is
http://www.cgal.org/Manual/latest/doc_html/cgal_manual/Triangulation_2/Chapter_main.html#Subsection_37.11.1
which shows for example how we can add color information to vertices.

Boost RTREE
http://www.boost.org/doc/libs/1_54_0/libs/geometry/doc/html/geometry/spatial_indexes/rtree_quickstart.html
uses something like std::pair<Box, MyGeometryId>. For the Apollonius
graph I do not see something similar. My first idea was to use a hash
map to map x, y coordinates of sites of the convex hull result to my
associated data structures (complex circular objects). I guess it may be
problematic due to rounding -- I may use two doubles to create a site
and as keys of my hash entry, but may get back a rounded double value
due to CGAL's intern exact arithmetic? 

#include <iostream>

#include <CGAL/MP_Float.h>
typedef CGAL::MP_Float NT;

#include <CGAL/Simple_cartesian.h>
typedef CGAL::Simple_cartesian<NT>  Kernel;
#include <CGAL/Apollonius_graph_2.h>
#include <CGAL/Apollonius_graph_traits_2.h>
typedef CGAL::Apollonius_graph_traits_2<Kernel>   Traits;
typedef CGAL::Apollonius_graph_2<Traits>          Apollonius_graph;
#include <CGAL/Apollonius_site_2.h>
typedef Apollonius_graph::Vertex_handle VH;
typedef Apollonius_graph::Site_2 Site;
typedef Site::Point_2                             Point;

class AG : public Apollonius_graph
{
public:
  int hash; // supported by Ruby hash
};

int main()
{
  AG ag;
  VH h;
  Point p;
  Site s;

  p = Point(0, 0);
  s = Site(p, 2);
  h = ag.insert(s);
  std::cout <<  h->site() << std::endl;

  p = Point(0, 1);
  s = Site(p, 2);
  ag.insert(s);
  p = Point(1, 0);
  s = Site(p, 2);
  ag.insert(s);
  p = Point(1, 1);
  s = Site(p, 2);
  ag.insert(s);
  p = Point(0.5, 0.5);
  s = Site(p, 2);
  ag.insert(s);
  p = Point(0.1, 0.1);
  s = Site(p, 2.2);
  ag.insert(s);

  Apollonius_graph::Vertex_circulator Cvert =
ag.incident_vertices(ag.infinite_vertex()); //take points incident to
infinte vertex
  Apollonius_graph::Vertex_circulator Cvert0 = Cvert;
  std::vector<Site> Vsite0;
  do{
    ++Cvert;
    std::cout <<  Cvert->site() << std::endl;
  }while(Cvert0!=Cvert);
  return 0;
}