Alpha_wrap_2/point_set_wrap_2.cpp

#define CGAL_AW2_DEBUG_PP
 
#include "output_helper.h"
 
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
 
#include <CGAL/alpha_wrap_2.h>
#include <CGAL/Multipolygon_with_holes_2.h>
 
#include <CGAL/Point_set_3.h>
#include <CGAL/IO/read_points.h>
#include <CGAL/IO/WKT.h>
#include <CGAL/Real_timer.h>
 
#include <iostream>
#include <string>
 
using K = CGAL::Exact_predicates_inexact_constructions_kernel;
using Point_2 = K::Point_2;
using Point_3 = K::Point_3;
using Vector_2 = K::Vector_2;
using Vector_3 = K::Vector_3;
 
using Point_set_2 = CGAL::Point_set_3<Point_2, Vector_2>;
using Point_set_3 = CGAL::Point_set_3<Point_3, Vector_3>;
 
using Multipolygon = CGAL::Multipolygon_with_holes_2<K>;
 
int main(int argc, char** argv)
{
  std::cout.precision(17);
  std::cerr.precision(17);
 
  const std::string filename = argc > 1 ? argv[1] : CGAL::data_file_path("points_3/circles.ply");
 
  // This code reads a _3D_ point file
  Point_set_3 point_set_3;
  if(!CGAL::IO::read_points(filename,
                            point_set_3.index_back_inserter(),
                            CGAL::parameters::point_map(point_set_3.point_push_map())))
  {
  std::cerr << "Can't read input file " << filename << std::endl;
  return EXIT_FAILURE;
  }
 
  // Project onto the xy plane
  Point_set_2 point_set_2;
  for (const auto& p3 : point_set_3.points())
    point_set_2.insert(Point_2(p3.x(), p3.y()));
 
  std::cout << point_set_2.size() << " points" << std::endl;
 
  // Compute the alpha and offset values
  const double relative_alpha = (argc > 2) ? std::stod(argv[2]) : 10.;
  const double relative_offset = (argc > 3) ? std::stod(argv[3]) : 300.;
 
  CGAL::Bbox_2 bbox;
  for (const auto& p2 : point_set_2.points())
    bbox += p2.bbox();
 
  std::ofstream proj_out("projected.xyz");
  proj_out.precision(std::numeric_limits<double>::max_digits10);
  for (const auto& p2 : point_set_2.points())
    proj_out << p2 << " 0\n";
  proj_out.close();
 
  const double diag_length = std::sqrt(CGAL::square(bbox.xmax() - bbox.xmin()) +
                                       CGAL::square(bbox.ymax() - bbox.ymin()));
  const double alpha = diag_length / relative_alpha;
  const double offset = diag_length / relative_offset;
  std::cout << "absolute alpha = " << alpha << " absolute offset = " << offset << std::endl;
 
  // Construct the wrap
  CGAL::Real_timer t;
  t.start();
 
  Multipolygon wrap;
  CGAL::alpha_wrap_2(point_set_2.points(), alpha, offset, wrap);
 
  t.stop();
  std::cout << "Result: " << wrap.polygons_with_holes().size() << " polygon(s)" << std::endl;
  std::cout << "Took " << t.time() << " s." << std::endl;
 
  // Save the result
  const std::string output_name = generate_output_name(filename, relative_alpha, relative_offset);
  std::cout << "Writing to " << output_name << std::endl;
 
  std::ofstream out(output_name);
  out.precision(std::numeric_limits<double>::max_digits10);
  CGAL::IO::write_multi_polygon_WKT(out, wrap);
 
  std::cout << "Done." << std::endl;
 
  return EXIT_SUCCESS;
}