Surface_mesh_simplification/edge_collapse_enriched_polyhedron.cpp

#include <iostream>
#include <fstream>

#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polyhedron_3.h>
// Extended polyhedron items which include an id() field
#include <CGAL/Polyhedron_items_with_id_3.h>

#include <CGAL/Surface_mesh_simplification/edge_collapse.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Count_ratio_stop_predicate.h>


typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_3 Point;

// Setup an enriched polyhedron type which stores an id() field in the items
typedef CGAL::Polyhedron_3<Kernel,CGAL::Polyhedron_items_with_id_3> Surface_mesh;

typedef boost::graph_traits<Surface_mesh>::halfedge_descriptor halfedge_descriptor;
typedef boost::graph_traits<Surface_mesh>::vertex_descriptor vertex_descriptor;

namespace SMS = CGAL::Surface_mesh_simplification;


int main( int argc, char** argv )
{
  Surface_mesh surface_mesh;

  std::ifstream is(argv[1]);
  is >> surface_mesh;
  if (!CGAL::is_triangle_mesh(surface_mesh)){
    std::cerr << "Input geometry is not triangulated." << std::endl;
    return EXIT_FAILURE;
  }

  // The items in this polyhedron have an "id()" field
  // which the default index maps used in the algorithm
  // need to get the index of a vertex/edge.
  // However, the Polyhedron_3 class doesn't assign any value to
  // this id(), so we must do it here:
  int index = 0;

  for(halfedge_descriptor hd : halfedges(surface_mesh)){
    hd->id() = index++;
}
  index = 0;

  for(vertex_descriptor vd : vertices(surface_mesh)){
    vd->id() = index++;
}

  // In this example, the simplification stops when the number of undirected edges
  // drops below 10% of the initial count
  SMS::Count_ratio_stop_predicate<Surface_mesh> stop(0.1);


  // The index maps are not explicitelty passed as in the previous
  // example because the surface mesh items have a proper id() field.
  // On the other hand, we pass here explicit cost and placement
  // function which differ from the default policies, ommited in
  // the previous example.
  int r = SMS::edge_collapse(surface_mesh, stop);

  std::cout << "\nFinished...\n" << r << " edges removed.\n"
            << (surface_mesh.size_of_halfedges()/2) << " final edges.\n";

  std::ofstream os( argc > 2 ? argv[2] : "out.off" );
  os.precision(17);
  os << surface_mesh;

  return EXIT_SUCCESS;
}