Alpha_wrap_3/triangle_soup_wrap.cpp

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Surface_mesh.h>
 
#include <CGAL/alpha_wrap_3.h>
#include <CGAL/Polygon_mesh_processing/bbox.h>
#include <CGAL/IO/polygon_soup_io.h>
#include <CGAL/Real_timer.h>
 
#include <array>
#include <iostream>
#include <string>
#include <vector>
 
namespace AW3 = CGAL::Alpha_wraps_3;
 
using K = CGAL::Exact_predicates_inexact_constructions_kernel;
using Point_3 = K::Point_3;
 
using Mesh = CGAL::Surface_mesh<Point_3>;
 
int main(int argc, char** argv)
{
  std::cout.precision(17);
 
  // Read the input
  const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/blobby-shuffled.off");
  std::cout << "Reading " << filename << "..." << std::endl;
 
  std::vector<Point_3> points;
  std::vector<std::array<std::size_t, 3> > faces;
  if(!CGAL::IO::read_polygon_soup(filename, points, faces) || faces.empty())
  {
    std::cerr << "Invalid input." << std::endl;
    return EXIT_FAILURE;
  }
 
  std::cout << "Input: " << points.size() << " points, " << faces.size() << " faces" << std::endl;
 
  // Compute the alpha and offset values
  const double relative_alpha = (argc > 2) ? std::stod(argv[2]) : 20.;
  const double relative_offset = (argc > 3) ? std::stod(argv[3]) : 600.;
 
  CGAL::Bbox_3 bbox;
  for(const Point_3& p : points)
    bbox += p.bbox();
 
  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;
 
  // Construct the wrap
  CGAL::Real_timer t;
  t.start();
 
  Mesh wrap;
  CGAL::alpha_wrap_3(points, faces, 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;
}