如何在CGAL中迭代面

你可以用 Delaunay::triangle 从面(迭代器)转换为相应的三角形。根据CGAL 3.8:

// points.cin contains point pairs, e.g.,
// 3 5 
// 0 0
// 1 9
// ...
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>
#include <fstream>

typedef CGAL::Exact_predicates_exact_constructions_kernel K;
typedef CGAL::Delaunay_triangulation_2<K> Delaunay;
typedef K::Point_2   Point;

int main()
{
  std::ifstream in("points.cin");
  std::istream_iterator<Point> begin(in);
  std::istream_iterator<Point> end;

  Delaunay dt;
  dt.insert(begin, end);

  Delaunay::Finite_faces_iterator it;
  for (it = dt.finite_faces_begin(); it != dt.finite_faces_end(); it++)
  {
    std::cout << dt.triangle(it) << std::endl;
  }

  return 0;
}

它 国际直拨电话 是顶点数(0、1或2)。在下面的示例中,顶点是一个点2对象,可以使用x()和y()方法访问其笛卡尔坐标。

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Triangulation_euclidean_traits_2.h>
#include <CGAL/Delaunay_triangulation_2.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Triangulation_euclidean_traits_2<K> Gt;
typedef CGAL::Delaunay_triangulation_2<Gt> Delaunay;

typedef K::Point_2 Point_2;
typedef std::vector<Point_2> Points;

int main()
{
    Points points;
    points.push_back(Point_2(0,0));
    points.push_back(Point_2(0,7));
    points.push_back(Point_2(7,0));
    points.push_back(Point_2(7,7));

    Delaunay dt(points.begin(), points.end());

    // Print Cartesian coordinates of vertices of triangles in 2D Delaunay triangulation
    for (Delaunay::Finite_faces_iterator it = dt.finite_faces_begin(); it != dt.finite_faces_end(); it++)
    {
        std::cout << " " << dt.triangle(it)[0].x() << " " << dt.triangle(it)[0].y() << " ";
        std::cout << " " << dt.triangle(it)[1].x() << " " << dt.triangle(it)[1].y() << " ";
        std::cout << " " << dt.triangle(it)[2].x() << " " << dt.triangle(it)[2].y() << " ";
        std::cout << std::endl << "-------------------" << std::endl;
    }
    return 0;
}

这是谷歌的一个例子。有限面迭代器被排版。

  Interval_skip_list isl;
  for(Finite_faces_iterator fh = dt.finite_faces_begin();
      fh != dt.finite_faces_end();
      ++fh){
    isl.insert(Interval(fh));
  }
  std::list<Interval> level;
  isl.find_intervals(50, std::back_inserter(level));
  for(std::list<Interval>::iterator it = level.begin();
      it != level.end();
      ++it){
    std::cout << dt.triangle(it->face_handle()) << std::endl;
  }

如果您想要一个真正扩展的示例来说明如何准确地执行您想要的操作,请从这里查看X平面场景工具的源代码: http://scenery.x-plane.com/code.php

嗯,我有一个类似的问题,我做了很多研究(主要是因为我没有任何关于C++的知识)。我想通过它的顶点整数表示来打印三角形。下面是它的外观:

#include <CGAL/Surface_mesh_default_triangulation_3.h>
#include <CGAL/Complex_2_in_triangulation_3.h>
#include <CGAL/make_surface_mesh.h>
#include <CGAL/Implicit_surface_3.h>

// This is the file where you can look for an example of iterating, geting basic vertex positions, outputing triangles
// #include <CGAL/IO/Complex_2_in_triangulation_3_file_writer.h>

// default triangulation for Surface_mesher
typedef CGAL::Surface_mesh_default_triangulation_3 Tr;

// c2t3
typedef CGAL::Complex_2_in_triangulation_3<Tr> C2t3;

typedef Tr::Geom_traits GT;
typedef GT::Sphere_3 Sphere_3;
typedef GT::Point_3 Point_3;
typedef GT::FT FT;

typedef FT (*Function)(Point_3);

typedef CGAL::Implicit_surface_3<GT, Function> Surface_3;

// This already have been defined
//typedef typename C2t3::Triangulation Tr;
typedef typename Tr::Vertex_handle Vertex_handle;
typedef typename Tr::Finite_vertices_iterator Finite_vertices_iterator;
typedef typename Tr::Finite_facets_iterator Finite_facets_iterator;

typedef typename Tr::Point Point;


FT sphere_function (Point_3 p) {
  const FT x = p.x();
  const FT y = p.y();
  const FT z = p.z();

  //const FT x2=p.x()*p.x(), y2=p.y()*p.y(), z2=p.z()*p.z();
  const FT a = 2;
  const FT b = 1;
  const FT c = 1.5;
  return x*x/a/a + y*y/b/b + z*z/c/c -1;
}

int main() {
  Tr tr;            // 3D-Delaunay triangulation
  C2t3 c2t3 (tr);   // 2D-complex in 3D-Delaunay triangulation

  // defining the surface
  Surface_3 surface(sphere_function,             // pointer to function
                    Sphere_3(CGAL::ORIGIN, 2.)); // bounding sphere
  // Note that "2." above is the *squared* radius of the bounding sphere!

  // defining meshing criteria
  CGAL::Surface_mesh_default_criteria_3<Tr> criteria(30.,  // angular bound
                                                     0.1,  // radius bound
                                                     0.1); // distance bound
  // meshing surface
  CGAL::make_surface_mesh(c2t3, surface, criteria, CGAL::Non_manifold_tag());

  std::cout << "Final number of points: " << tr.number_of_vertices() << "\n";

  // Here should be the main code

  Tr& tr2 = c2t3.triangulation();

  std::map<Vertex_handle, int> V;
  int inum = 0;
  Finite_vertices_iterator vit = tr2.finite_vertices_begin();
  while(vit != tr2.finite_vertices_end()) {

    // making an integer representation of vertex pointers
    V[vit] = inum++;

    // obtaining vertex positions from vertex pointer vit
    Point p = static_cast<Point>(vit->point());
    std::cout << p.x() << " " << p.y() << " " << p.z() << std::endl;

    ++vit;
  }

  Finite_facets_iterator fit = tr2.finite_facets_begin();

  while (fit != tr2.finite_facets_end()) {

    typename Tr::Cell_handle cell = fit->first;
    const int& index = fit->second;

    int index1 = V[cell->vertex(tr.vertex_triple_index(index, 0))];
    int index2 = V[cell->vertex(tr.vertex_triple_index(index, 1))];
    int index3 = V[cell->vertex(tr.vertex_triple_index(index, 2))];

    std::cout << index1 << " " << index2 << " " << index3 << std::endl;
    ++fit;
  }

}

用(如果 mesh_implicit_function 是源、对象文件和可执行文件):

c++   -DCGAL_USE_GMP -DCGAL_USE_MPFR -DCGAL_USE_ZLIB -frounding-math -o mesh_an_implicit_function.cpp.o -c mesh_an_implicit_function.cpp
c++ mesh_an_implicit_function.cpp.o  -o mesh_an_implicit_function -lmpfr -lgmp -lCGAL -lboost_thread