CGAL - Recupera l'indice Vertex dopo la triangolazione del delaunay

Question

Sto calcolando la triangolazione 2D Delaunay di alcune migliaia di punti. Ogni punto ha più dati associati ad esso oltre le coordinate X e Y. Pertanto, mi chiedevo se fosse possibile recuperare l'indice di ciascun punto in modo da poter accedere alla mia struttura in un altro vettore.

Attualmente, poiché accedo ai vertici da un face_handle, restituisce un punto (cioè coordinate y, y) Come posso restituire ogni vertice dal suo ID (indice) invece delle sue coordinate x, y? Grazie.

#include <vector>
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef CGAL::Delaunay_triangulation_2<Kernel> Delaunay;
typedef Kernel::Point_2 Point;

void example() {

  std::vector<Point> points;
  points.push_back(Point(1,1)); //index 0
  points.push_back(Point(1,2)); //index 1
  points.push_back(Point(1,3)); //index 2
  points.push_back(Point(2,1)); //index 3
  points.push_back(Point(2,2)); //index 4
  points.push_back(Point(2,3)); //index 5

  Delaunay triangulation;
  triangulation.insert(points.begin(),points.end());

  for(Delaunay::Finite_faces_iterator fit = triangulation.finite_faces_begin();
      fit != triangulation.finite_faces_end(); ++fit) {

    Delaunay::Face_handle face = fit;
    std::cout << "Triangle:\t" << triangulation.triangle(face) << std::endl;
    std::cout << "Vertex 0:\t" << triangulation.triangle(face)[0] << std::endl;
  }
}

Output (coordinate x, y):

Triangle:   1 3 1 2 2 2
Vertex 0:   1 3
Triangle:   1 2 1 1 2 1
Vertex 0:   1 2
Triangle:   1 3 2 2 2 3
Vertex 0:   1 3
Triangle:   1 2 2 1 2 2
Vertex 0:   1 2

Output desiderato (indici):

Triangle:   2   1   4
Vertex 0:   2
Triangle:   1   0   3
Vertex 0:   1 
Triangle:   2   4   5
Vertex 0:   2
Triangle:   1   3   4
Vertex 0:   1

Answer 1

È possibile allegare qualsiasi informazione ai vertici in una triangolazione. Ad esempio per aggiungere indici (unsigned int) potresti fare quanto segue:

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>
#include <CGAL/Triangulation_vertex_base_with_info_2.h>
#include <vector>

typedef CGAL::Exact_predicates_inexact_constructions_kernel            Kernel;
typedef CGAL::Triangulation_vertex_base_with_info_2<unsigned int, Kernel> Vb;
typedef CGAL::Triangulation_data_structure_2<Vb>                       Tds;
typedef CGAL::Delaunay_triangulation_2<Kernel, Tds>                    Delaunay;
typedef Kernel::Point_2                                                Point;

int main() {

  std::vector< std::pair<Point,unsigned> > points;
  points.push_back( std::make_pair( Point(1,1), 0 ) );
  points.push_back( std::make_pair( Point(1,2), 1 ) );
  points.push_back( std::make_pair( Point(1,3), 2 ) );
  points.push_back( std::make_pair( Point(2,1), 3 ) );
  points.push_back( std::make_pair( Point(2,2), 4 ) );
  points.push_back( std::make_pair( Point(2,3), 5 ) );

  Delaunay triangulation;
  triangulation.insert(points.begin(),points.end());

  for(Delaunay::Finite_faces_iterator fit = triangulation.finite_faces_begin();
      fit != triangulation.finite_faces_end(); ++fit) {

    Delaunay::Face_handle face = fit;
    std::cout << "Triangle:\t" << triangulation.triangle(face) << std::endl;
    std::cout << "Vertex 0:\t" << triangulation.triangle(face)[0] << std::endl;
    std::cout << "Vertex 0:\t" << face->vertex(0)->info() << std::endl;
  }
}