Surface_mesh_simplification/edge_collapse_constrained_border_surface_mesh.cpp

#include <iostream>
#include <fstream>
#include <map>

#include <CGAL/Simple_cartesian.h>
#include <CGAL/Surface_mesh.h>

// Simplification function
#include <CGAL/Surface_mesh_simplification/edge_collapse.h>

// Midpoint placement policy
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Midpoint_placement.h>

//Placement wrapper
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Constrained_placement.h>

// Stop-condition policy
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Count_stop_predicate.h>

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

typedef CGAL::Surface_mesh<Point_3> Surface_mesh; 
typedef boost::graph_traits<Surface_mesh>::halfedge_descriptor halfedge_descriptor;
typedef boost::graph_traits<Surface_mesh>::edge_descriptor edge_descriptor;

namespace SMS = CGAL::Surface_mesh_simplification ;

//
// BGL property map which indicates whether an edge is marked as non-removable
//
struct Border_is_constrained_edge_map{
  const Surface_mesh* sm_ptr;
  typedef edge_descriptor key_type;
  typedef bool value_type;
  typedef value_type reference;
  typedef boost::readable_property_map_tag category;

  Border_is_constrained_edge_map(const Surface_mesh& sm)
    : sm_ptr(&sm)
  {}

  friend bool get(Border_is_constrained_edge_map m, const key_type& edge) {
    return  CGAL::is_border(edge, *m.sm_ptr);
  }
};

//
// Placement class
//
typedef SMS::Constrained_placement<SMS::Midpoint_placement<Surface_mesh>,
                                   Border_is_constrained_edge_map > Placement;

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

  if (argc!=2){
    std::cerr << "Usage: " << argv[0] << " input.off\n";
    return EXIT_FAILURE;
  }

  std::ifstream is(argv[1]);
  if(!is){
    std::cerr << "Filename provided is invalid\n";
    return EXIT_FAILURE;
  }

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

  Surface_mesh::Property_map<halfedge_descriptor,std::pair<Point_3, Point_3> > constrained_halfedges;

  constrained_halfedges = surface_mesh.add_property_map<halfedge_descriptor,std::pair<Point_3, Point_3> >("h:vertices").first;

  std::size_t nb_border_edges=0;
  BOOST_FOREACH(halfedge_descriptor hd, halfedges(surface_mesh)){
    if(CGAL::is_border(hd,surface_mesh)){
      constrained_halfedges[hd] = std::make_pair(surface_mesh.point(source(hd,surface_mesh)),
                                                 surface_mesh.point(target(hd,surface_mesh)));
      ++nb_border_edges;
    }
  }

  // Contract the surface mesh as much as possible
  SMS::Count_stop_predicate<Surface_mesh> stop(0);

  Border_is_constrained_edge_map bem(surface_mesh);
  
  // This the actual call to the simplification algorithm.
  // The surface mesh and stop conditions are mandatory arguments.
  int r = SMS::edge_collapse
            (surface_mesh
            ,stop
             ,CGAL::parameters::edge_is_constrained_map(bem)
                               .get_placement(Placement(bem))
            );

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

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

  // now check!
  BOOST_FOREACH(halfedge_descriptor hd, halfedges(surface_mesh)){
    if(CGAL::is_border(hd,surface_mesh)){
      --nb_border_edges;
      if(constrained_halfedges[hd] != std::make_pair(surface_mesh.point(source(hd,surface_mesh)),
                                                     surface_mesh.point(target(hd,surface_mesh)))){
        std::cerr << "oops. send us a bug report\n";
      }

    }
  }
  assert( nb_border_edges==0 );

  return EXIT_SUCCESS ;
}