Surface_mesh_simplification/edge_collapse_enriched_polyhedron.cpp

#include <iostream>
#include <fstream>

#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polyhedron_3.h>

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

// Visitor base
#include <CGAL/Surface_mesh_simplification/Edge_collapse_visitor_base.h>

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

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

// Non-default cost and placement policies
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Midpoint_and_length.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 Surface_mesh::Halfedge_handle Halfedge_handle ;
typedef Surface_mesh::Vertex_handle   Vertex_handle ;

namespace SMS = CGAL::Surface_mesh_simplification ;

typedef SMS::Edge_profile<Surface_mesh> Profile ;


// The following is a Visitor that keeps track of the simplification process.
// In this example the progress is printed real-time and a few statistics are
// recorded (and printed in the end).
//
struct Stats
{
  Stats() 
    : collected(0)
    , processed(0)
    , collapsed(0)
    , non_collapsable(0)
    , cost_uncomputable(0) 
    , placement_uncomputable(0) 
  {} 
  
  std::size_t collected ;
  std::size_t processed ;
  std::size_t collapsed ;
  std::size_t non_collapsable ;
  std::size_t cost_uncomputable  ;
  std::size_t placement_uncomputable ; 
} ;

struct My_visitor : SMS::Edge_collapse_visitor_base<Surface_mesh>
{
  My_visitor( Stats* s) : stats(s){} 

  // Called during the collecting phase for each edge collected.
  void OnCollected( Profile const&, boost::optional<double> const& )
  {
    ++ stats->collected ;
    std::cerr << "\rEdges collected: " << stats->collected << std::flush ;
  }                
  
  // Called during the processing phase for each edge selected.
  // If cost is absent the edge won't be collapsed.
  void OnSelected(Profile const&          
                 ,boost::optional<double> cost
                 ,std::size_t             initial
                 ,std::size_t             current
                 )
  {
    ++ stats->processed ;
    if ( !cost )
      ++ stats->cost_uncomputable ;
      
    if ( current == initial )
      std::cerr << "\n" << std::flush ;
    std::cerr << "\r" << current << std::flush ;
  }                
  
  // Called during the processing phase for each edge being collapsed.
  // If placement is absent the edge is left uncollapsed.
  void OnCollapsing(Profile const&          
                   ,boost::optional<Point>  placement
                   )
  {
    if ( !placement )
      ++ stats->placement_uncomputable ;
  }                
  
  // Called for each edge which failed the so called link-condition,
  // that is, which cannot be collapsed because doing so would
  // turn the surface mesh into a non-manifold.
  void OnNonCollapsable( Profile const& )
  {
    ++ stats->non_collapsable;
  }                
  
  // Called AFTER each edge has been collapsed
  void OnCollapsed( Profile const&, Vertex_handle )
  {
    ++ stats->collapsed;
  }                
  
  Stats* stats ;
} ;


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( Surface_mesh::Halfedge_iterator eb = surface_mesh.halfedges_begin()
     , ee = surface_mesh.halfedges_end()
     ; eb != ee
     ; ++ eb
     ) 
    eb->id() = index++;

  index = 0 ;
  for( Surface_mesh::Vertex_iterator vb = surface_mesh.vertices_begin()
     , ve = surface_mesh.vertices_end()
     ; vb != ve
     ; ++ vb
     ) 
    vb->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);
 
  Stats stats ;
  
  My_visitor vis(&stats) ;
    
  // 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
            ,CGAL::parameters::get_cost     (SMS::Edge_length_cost  <Surface_mesh>())
                              .get_placement(SMS::Midpoint_placement<Surface_mesh>())
                              .visitor      (vis)
           );
  
  std::cout << "\nEdges collected: "  << stats.collected
            << "\nEdges proccessed: " << stats.processed
            << "\nEdges collapsed: "  << stats.collapsed
            << std::endl
            << "\nEdges not collapsed due to topological constraints: "  << stats.non_collapsable
            << "\nEdge not collapsed due to cost computation constraints: "  << stats.cost_uncomputable 
            << "\nEdge not collapsed due to placement computation constraints: " << stats.placement_uncomputable 
            << std::endl ; 
            
  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 << surface_mesh ;
  
  return EXIT_SUCCESS ;      
}