Alpha_wrap_3/point_set_wrap.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
 
#include <CGAL/alpha_wrap_3.h>
#include <CGAL/IO/read_points.h>
#include <CGAL/Real_timer.h>
 
#include <iostream>
#include <string>
 
using K = CGAL::Exact_predicates_inexact_constructions_kernel;
using Point_3 = K::Point_3;
 
using Point_container = std::vector<Point_3>;
using Mesh = CGAL::Surface_mesh<Point_3>;
 
int main(int argc, char** argv)
{
  // Read the input
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("points_3/oni.pwn");
  std::cout << "Reading " << filename << "..." << std::endl;
 
  Point_container points;
  if(!CGAL::IO::read_points(filename, std::back_inserter(points)) || points.empty())
  {
    std::cerr << "Invalid input." << std::endl;
    return EXIT_FAILURE;
  }
 
  std::cout << points.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_3 bbox = CGAL::bbox_3(std::cbegin(points), std::cend(points));
  const double diag_length = std::sqrt(CGAL::square(bbox.xmax() - bbox.xmin()) +
                                       CGAL::square(bbox.ymax() - bbox.ymin()) +
                                       CGAL::square(bbox.zmax() - bbox.zmin()));
  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();
 
  Mesh wrap;
  CGAL::alpha_wrap_3(points, alpha, offset, wrap);
 
  t.stop();
  std::cout << "Result: " << num_vertices(wrap) << " vertices, " << num_faces(wrap) << " faces" << std::endl;
  std::cout << "Took " << t.time() << " s." << std::endl;
 
  // Save the result
  std::string input_name = std::string(filename);
  input_name = input_name.substr(input_name.find_last_of("/") + 1, input_name.length() - 1);
  input_name = input_name.substr(0, input_name.find_last_of("."));
  std::string output_name = input_name + "_" + std::to_string(static_cast<int>(relative_alpha))
                            + "_" + std::to_string(static_cast<int>(relative_offset)) + ".off";
  std::cout << "Writing to " << output_name << std::endl;
  CGAL::IO::write_polygon_mesh(output_name, wrap, CGAL::parameters::stream_precision(17));
 
  return EXIT_SUCCESS;
}