CGAL：无法正确选择迭代器

Question

我在 CGAL 库中从流 .txt 文件中的点构建了一个凸包 3d，并希望通过复制将它们插入到输出 .txt 文件中。问题是要为 std::copy 选择迭代器，它可以对容器 Polyhedron_3 poly 中的顶点进行排序。这是我的代码：

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/point_generators_3.h>
#include <CGAL/algorithm.h>
#include <CGAL/Polyhedron_3.h>
#include <CGAL/convex_hull_3.h>
#include <vector>
#include <fstream>

typedef CGAL::Exact_predicates_inexact_constructions_kernel  K;
typedef CGAL::Polyhedron_3<K>                     Polyhedron_3;
typedef K::Segment_3                              Segment_3;
// define point creator
typedef K::Point_3                                Point_3;
typedef CGAL::Creator_uniform_3<double, Point_3>  PointCreator;
//a functor computing the plane containing a triangular facet
struct Plane_from_facet {
  Polyhedron_3::Plane_3 operator()(Polyhedron_3::Facet& f) {
      Polyhedron_3::Halfedge_handle h = f.halfedge();
      return Polyhedron_3::Plane_3( h->vertex()->point(),
                                    h->next()->vertex()->point(),
                                    h->opposite()->vertex()->point());
  }
};

using namespace std;

int main()
{

  std::ifstream fin("/Users/Arseniy/Documents/Course Work/Test Input.txt");
  std::ofstream fout("/Users/Arseniy/Documents/Course Work/Test Output.txt");

  CGAL::set_ascii_mode(fin);
  CGAL::set_ascii_mode(fout);

  std::istream_iterator< Point_3 >  in_start(fin );
  std::istream_iterator< Point_3 >  in_end;
  std::ostream_iterator< Point_3 >  out( fout, "\n" );

  std::vector<Point_3> points;
  std::copy(in_start, in_end, std::back_inserter(points));

  Polyhedron_3 poly;

  // compute convex hull of non-collinear points
  CGAL::convex_hull_3(points.begin(), points.end(), poly);

  cout << "The convex hull contains " << poly.size_of_vertices() << " vertices" << std::endl;
  cout << "The convex hull contains " << poly.size_of_facets() << " facets" << std::endl;

  // assign a plane equation to each polyhedron facet using functor Plane_from_facet
  std::transform(poly.facets_begin(), poly.facets_end(), poly.planes_begin(),Plane_from_facet());

  std::copy(poly.vertices_begin(), poly.vertices_end(), ostream_iterator<int>(fout, ", "));

  return 0;
}

我无法确定 ostream_iterator<> 的类型，它应该是 vertex_iterator，但不是。

我也试图描述

typedef Polyhedron::Vertex_iterator

但这也是一个错误的决定。

Answer 1

可以使用OFF 文件格式将多面体写入文件。你可以简单地写：

std::ofstream fout("output.off");
fout << poly;

根据您的 CGAL 版本，您可能需要包含 CGAL/IO/Polyhedron_iostream.h

Answer 2

应该这样做：

std::copy(poly.points_begin(), poly.points_end(), ostream_iterator<Point_3>(fout, ", "));

CGAL：无法正确选择迭代器

CGAL: can't chose iterator correctly

c++

cgal

c++11