Segment Delaunay Graph

sdg.cpp

#include <iostream>
#include <fstream>
#include <cassert>

// example that uses the filtered traits,
// the segment Delaunay graph and the spatial sorting

// choose the kernel
#include <CGAL/Simple_cartesian.h>

typedef CGAL::Simple_cartesian<double> K;

// typedefs for the traits and the algorithm
#include <CGAL/Segment_Delaunay_graph_2.h>
#include <CGAL/Segment_Delaunay_graph_filtered_traits_2.h>

typedef CGAL::Segment_Delaunay_graph_filtered_traits_2<K> Gt;
typedef CGAL::Segment_Delaunay_graph_2<Gt>  SDG2;


int main(int argc, char* argv[])
{
  std::ifstream ifs(argv[1]);
  assert( ifs );

  //polygon points
  std::vector<Gt::Point_2> points;
  //segments of the polygon as a pair of point indices
  std::vector<std::pair<std::size_t,std::size_t> > indices;

  SDG2::Site_2 site;
  //read a close polygon given by its segments
  // s x0 y0 x1 y1
  // s x1 y1 x2 y2
  // ...
  // s xn yn x0 y0
  Gt::Point_2 p,q;
  ifs >> p;
  points.push_back(p);
  while(ifs >> q){
    if(p == q){
      std::cerr << "duplicate point: " << p << std::endl;
    }else{
      points.push_back(q);
      p = q;
    }
  }
  if(points.front() == points.back()){
    points.pop_back();
  }
  for(int i=0; i < points.size()-1; i++){
      indices.push_back( std::make_pair(i, i+1) );
    }
  ifs.close();

  SDG2          sdg;

  //insert the polygon segments all at once using spatial sorting to speed the insertion
  sdg.insert_segments( points.begin(), points.end(), indices.begin(), indices.end() );

  // validate the segment Delaunay graph
  if(sdg.is_valid(true, 1) ){
    std::cerr << "SDG is valid" << std::endl;
  }

  return 0;
}