CGAL users discussion list

[Ben Strasser <>]

Hello,

I'm trying to iterator over the boundaries of the facets of a Voronoi
diagram and have run into a CGAL behavior I can not explain. I build the
diagram of the points (1, 1), (-1, 1), (-1, -1) and (1, -1). Then I just
print out what objects CGAL gives me.

seg:-0 -0 -0 -0
ray:-0 -0 4 -0
ray:-0 -0 -0 4
 --- 
ray:-0 -0 -4 -0
ray:-0 -0 -0 4
 --- 
ray:-0 -0 -0 -4
seg:-0 -0 -0 -0
ray:-0 -0 -4 -0
 --- 
ray:-0 -0 -0 -4
ray:-0 -0 4 -0
 --- 

The rays are correct as each of the 4 facets is delimited by 2 rays.
However what is a segment starting at the origin and ending at the origin
supposed to mean. Did I run into a bug? Can anyone reproduce this?

My compiler: gcc version 4.4.1 (Ubuntu 4.4.1-4ubuntu8)
CGAL version: 
#define CGAL_VERSION 3.4
#define CGAL_VERSION_NR 1030401000
#define CGAL_SVN_REVISION 47779
(that's the current ubuntu package)

Below is a minimal example that produces the output above.

thanks for your time,
Ben Strasser






#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>
typedef CGAL::Exact_predicates_exact_constructions_kernel Kernel;
typedef CGAL::Segment_2<Kernel> Segment;
typedef CGAL::Ray_2<Kernel> Ray;
typedef CGAL::Point_2<Kernel> Point;
typedef CGAL::Line_2<Kernel> Line;
typedef CGAL::Delaunay_triangulation_2<Kernel> Triangulation;
        
#include<cassert>
#include<iostream>
using std::cout;
using std::endl;

int main(){
        Point voronoi[] = {Point(1, 1), Point(-1, 1), Point(-1, -1), Point(1,
-1)};

        Triangulation t;
        t.insert(voronoi[0]);
        t.insert(voronoi[1]);
        t.insert(voronoi[2]);
        t.insert(voronoi[3]);

        for(Triangulation::Finite_vertices_iterator 
i=t.finite_vertices_begin(),
i_end=t.finite_vertices_end(); i!=i_end; ++i){          
                Triangulation::Edge_circulator c = t.incident_edges(i), e;
                assert(c != NULL);
                
                while(t.is_infinite(*c))
                        ++c;    
                e = c;  
                do{
                        
                        CGAL::Object obj = t.dual(c);
                        const Segment*seg = CGAL::object_cast<Segment>(&obj);
                        const Ray*ray = CGAL::object_cast<Ray>(&obj);
                        const Line*line = CGAL::object_cast<Line>(&obj);

                        if(seg) cout << "seg:" << *seg <<endl;
                        if(ray) cout << "ray:" << *ray <<endl;
                        if(line) cout << "line:" << *line <<endl;

                        ++c;
                        while(t.is_infinite(*c))
                                ++c;

                }while(c != e);
                cout << " --- " << endl;        
        }

}