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[魏华祎 <>]

Hi, Sebastien,

    Thanks for your reply. Yes, you are right, the infinite vertex is already present there. But, what about the infinite faces? Do I need create them explicitly? The output of tri.number_of_faces() is still three. It should be two.

     

Huayi

On Sun, May 22, 2011 at 11:29 PM, Sebastien Loriot (GeometryFactory) <sloriot.ml@gmail.com> wrote:

The infinite vertex is already present in the triangulation even when empty, so you don't need to create it.

S.

魏华祎 wrote:

 Hi, everyone,
          I have a 2d simple triangulation with four vertices: p1 = (0,0),  p2 = (1,0), p3  = (1,1), p4 = ( 0,1),  and two triangles: (p2, p3, p1) and (p4,p1,p3). And I want to construct a object of Triangulation_2 class, explicitly ( not write these information into files, then use >> read them). The following is my code. But at last, I got five finite vertices and three finite faces. I am confused,  can anyone give me some suggestions about it?  Thanks very much!

   By the way, I follow the code of  the "file_input" member function in Triangulation_data_structure_2.h to write my own code.



#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/IO/Color.h>
#include <CGAL/Triangulation_2.h>

#include <CGAL/Triangulation_face_base_2.h>
#include <CGAL/Triangulation_vertex_base_2.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Triangulation_vertex_base_2<K> Vb;
typedef CGAL::Triangulation_face_base_2<K> Fb;
typedef CGAL::Triangulation_data_structure_2<Vb,Fb> Tds;
typedef CGAL::Triangulation_2<K,Tds> Triangulation;

typedef Triangulation::Face_handle Face_handle;
typedef Triangulation::Vertex_handle Vertex_handle;
typedef Triangulation::Point Point;

typedef Triangulation::Finite_vertices_iterator Fvi;

int main(){


 int n = 4, m = 2, d = 2;
 std::vector<Point> P(4);
 P[0] = Point(0,0);
 P[1] = Point(1,0);
 P[2] = Point(1,1);
 P[3] = Point(0,1);

 std::vector<Vertex_handle> V(n+1);
 std::vector<Face_handle> F(m);

 Triangulation tri;
 tri.tds().set_dimension(d);
 // if I comment the following two lines, there will four finite vertices, but still three faces
 V[0] = tri.tds().create_vertex();   tri.set_infinite_vertex(V[0]); // set the infinite vertex of tri

 // create the vertex_handles
 for(int i = 1; i< 5;i++){
   V[i] = tri.tds().create_vertex();
   V[i]->set_point(P[i-1]);
 }

 //create the first face and set its vertices
 F[0] = tri.create_face();
 F[0]->set_vertex(0,V[2]);
 V[2]->set_face(F[0]);

 F[0]->set_vertex(1,V[3]);
 V[3]->set_face(F[0]);

 F[0]->set_vertex(2,V[1]);
 V[1]->set_face(F[0]);

 // create the second face and set its vertices
 F[1] = tri.create_face();
 F[1]->set_vertex(0,V[4]);
 V[4]->set_face(F[1]);

 F[1]->set_vertex(1,V[1]);
 V[1]->set_face(F[1]);
   F[1]->set_vertex(2,V[3]);
 V[3]->set_face(F[1]);

 // set neighbor information
 F[0]->set_neighbor(0,F[1]);
 F[1]->set_neighbor(0,F[0]);

 std::cout<<tri.number_of_vertices()<<std::endl<<tri.number_of_faces()<<std::endl;

 return 0;
}

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