Point_set_processing_3/edges_example.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/vcm_estimate_edges.h>
#include <CGAL/property_map.h>
#include <CGAL/IO/read_points.h>
 
#include <utility> // defines std::pair
#include <vector>
#include <fstream>
 
// Types
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef Kernel::Point_3 Point;
typedef Kernel::Vector_3 Vector;
 
// Point with normal vector stored in a std::pair.
typedef std::pair<Point, Vector> PointVectorPair;
typedef std::vector<PointVectorPair> PointList;
 
typedef std::array<double,6> Covariance;
 
int main (int , char**)
{
  // Reads a polygon mesh file in points[].
  std::list<PointVectorPair> points;
  if(!CGAL::IO::read_points(CGAL::data_file_path("meshes/fandisk_large.off"),
                            std::back_inserter(points),
                            CGAL::parameters::point_map(CGAL::First_of_pair_property_map<PointVectorPair>())))
  {
    std::cerr << "Error: cannot read file data/fandisk_large.off" << std::endl;
    return EXIT_FAILURE;
  }
 
  // Estimates covariance matrices per points.
  double R = 0.2,
         r = 0.1;
  std::vector<Covariance> cov;
  CGAL::First_of_pair_property_map<PointVectorPair> point_map;
 
  CGAL::compute_vcm(points, cov, R, r,
                    CGAL::parameters::point_map (point_map).geom_traits (Kernel()));
 
  // Find the points on the edges.
  // Note that this step is not expensive and can be done several time to get better results
  double threshold = 0.16;
  std::ofstream output("points_on_edges.xyz");
  int i = 0;
  for(const PointVectorPair& p : points)
  {
    if(CGAL::vcm_is_on_feature_edge(cov[i], threshold))
      output << p.first << "\n";
    ++i;
  }
 
  return 0;
}