update example and add new one using the constrained edge map

Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_constrained_border_polyhedron.cmd

@@ -0,0 +1 @@
+mesh_with_border.off

Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_constrained_border_polyhedron.cpp

@@ -0,0 +1,129 @@
+#include <iostream>
+#include <fstream>
+#include <map>
+
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Polyhedron_3.h>
+#include <CGAL/IO/Polyhedron_iostream.h>
+
+// Adaptor for Polyhedron_3
+#include <CGAL/Surface_mesh_simplification/HalfedgeGraph_Polyhedron_3.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_wrapper.h>
+
+typedef CGAL::Simple_cartesian<double> Kernel;
+typedef Kernel::Point_3 Point_3;
+typedef CGAL::Polyhedron_3<Kernel> Surface;
+
+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{
+  typedef boost::graph_traits<Surface>::edge_descriptor key_type;
+  typedef bool value_type;
+  typedef value_type reference;
+  typedef boost::readable_property_map_tag category;
+  friend bool get(Border_is_constrained_edge_map, key_type edge) {
+    return edge->is_border_edge();
+  }
+};
+
+//
+// A stop predicate that never says to stop.
+//
+struct No_stop_predicate
+{
+  typedef Surface ECM;
+  typedef double FT;
+  typedef boost::graph_traits<ECM>::edges_size_type size_type;
+  typedef SMS::Edge_profile<Surface> Profile;
+
+  bool operator()( FT const&, Profile const&, size_type, size_type) const
+  {
+    return false;
+  }
+};
+
+//
+// Placement class
+//
+typedef SMS::Constrained_placement_wrapper<SMS::Midpoint_placement<Surface>,
+                                           Border_is_constrained_edge_map >
+  Placement;
+
+int main( int argc, char** argv )
+{
+  Surface surface;
+
+  if (argc!=2){
+    std::cerr<< "Usage: " << argv[0] << " input.off\n";
+    return 1;
+  }
+
+  std::ifstream is(argv[1]);
+  if(!is){
+    std::cerr<< "Filename provided is invalid\n";
+    return 1;
+  }
+
+  is >> surface ;
+
+  // map used to check that constrained_edges and the points of its vertices
+  // are preserved at the end of the simplification
+  std::map<Surface::Halfedge_handle,std::pair<Point_3, Point_3> >constrained_edges;
+  std::size_t nb_border_edges=0;
+
+  for (Surface::Halfedge_iterator hit=surface.halfedges_begin(),
+                                  hit_end=surface.halfedges_end(); hit!=hit_end;
+                                  ++hit )
+  {
+    if ( hit->is_border() ){
+      constrained_edges[hit]=std::make_pair( hit->opposite()->vertex()->point(),
+                                             hit->vertex()->point() );
+      ++nb_border_edges;
+    }
+  }
+
+  // This the actual call to the simplification algorithm.
+  // The surface and stop conditions are mandatory arguments.
+  // The index maps are needed because the vertices and edges
+  // of this surface lack an "id()" field.
+  int r = SMS::edge_collapse
+            (surface
+            ,No_stop_predicate()
+            ,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index,surface))
+                  .edge_index_map  (boost::get(CGAL::edge_external_index  ,surface))
+                  .edge_is_constrained_map(Border_is_constrained_edge_map())
+                  .get_placement(Placement())
+            );
+
+  std::cout << "\nFinished...\n" << r << " edges removed.\n"
+            << (surface.size_of_halfedges()/2) << " final edges.\n" ;
+
+  std::ofstream os( argc > 2 ? argv[2] : "out.off" ) ; os << surface ;
+
+  // now check!
+  for (Surface::Halfedge_iterator hit=surface.halfedges_begin(),
+                                  hit_end=surface.halfedges_end(); hit!=hit_end;
+                                  ++hit )
+  {
+    if (hit->is_border()){
+      --nb_border_edges;
+      assert( constrained_edges[hit] ==
+              std::make_pair( hit->opposite()->vertex()->point(),
+                              hit->vertex()->point() ) );
+    }
+  }
+  assert( nb_border_edges==0 );
+
+  return 0 ;
+}

Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_constrained_polyhedron.cpp

@@ -18,54 +18,50 @@
 #include <CGAL/Unique_hash_map.h>
 
 typedef CGAL::Simple_cartesian<double> Kernel;
-typedef CGAL::Polyhedron_3<Kernel> Surface; 
+typedef CGAL::Polyhedron_3<Kernel> Surface;
-
+typedef boost::graph_traits<Surface const>::edge_descriptor edge_descriptor;
 namespace SMS = CGAL::Surface_mesh_simplification ;
 
 //
-// BGL property map which indicates whether an edge is border OR is marked as non-removable
+// BGL property map which indicates whether an edge is marked as non-removable
 //
-class Constrains_map : public boost::put_get_helper<bool,Constrains_map>
+struct Constrained_edge_map : public boost::put_get_helper<bool,Constrained_edge_map>
 {
-public:
+  typedef boost::readable_property_map_tag      category;
+  typedef bool                                  value_type;
+  typedef bool                                  reference;
+  typedef edge_descriptor                       key_type;
 
-  typedef boost::readable_property_map_tag                    category;
+  Constrained_edge_map(const CGAL::Unique_hash_map<key_type,bool>& aConstraints)
-  typedef bool                                                value_type;
+    : mConstraints(aConstraints) {}
-  typedef bool                                                reference;
-  typedef boost::graph_traits<Surface const>::edge_descriptor key_type;
 
-  Constrains_map() : mConstrains(false) {}
+  reference operator[](key_type const& e) const { return  is_constrained(e); }
+
+  bool is_constrained( key_type const& e ) const {
+    return mConstraints.is_defined(e) ? mConstraints[e] : false ; }
 
-  reference operator[](key_type const& e) const { return e->is_border() || is_constrained(e) ; }
-  
-  void set_is_constrained ( key_type const& e, bool is )  { mConstrains[e]=is; }
-  
-  bool is_constrained( key_type const& e ) const { return mConstrains.is_defined(e) ? mConstrains[e] : false ; }
-  
 private:
-  
+  const CGAL::Unique_hash_map<key_type,bool>& mConstraints;
-  CGAL::Unique_hash_map<key_type,bool> mConstrains ;
-  
 };
 
-int main( int argc, char** argv ) 
+int main( int argc, char** argv )
 {
-  Surface surface; 
+  Surface surface;
-  
+
   std::ifstream is(argv[1]) ; is >> surface ;
 
   // This is a stop predicate (defines when the algorithm terminates).
   // In this example, the simplification stops when the number of undirected edges
   // left in the surface drops below the specified number (1000)
   SMS::Count_stop_predicate<Surface> stop(10);
-     
+
-  Constrains_map constrains_map ;
+  // This example marks ALL edges as non-removable, but a real world application would mark only selected ones.
-     
+  CGAL::Unique_hash_map<edge_descriptor,bool> constrained_edge_hmap;
-     
+  for( Surface::Halfedge_iterator eb = surface.halfedges_begin(), ee = surface.halfedges_end() ; eb != ee ; ++ eb )
-  // This example marks ALL edges as non-removable, but a real world application would mark only selected ones.   
+    constrained_edge_hmap[eb]=true;
-  for( Surface::Halfedge_iterator eb = surface.halfedges_begin(), ee = surface.halfedges_end() ; eb != ee ; ++ eb ) 
+
-    constrains_map.set_is_constrained(eb,true);
+  Constrained_edge_map constrained_edge_map(constrained_edge_hmap);
-     
+
   // This the actual call to the simplification algorithm.
   // The surface and stop conditions are mandatory arguments.
   // The index maps are needed because the vertices and edges
@@ -73,15 +69,15 @@ int main( int argc, char** argv )
   int r = SMS::edge_collapse
             (surface
             ,stop
-            ,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index,surface)) 
+            ,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index,surface))
-                  .edge_index_map  (boost::get(CGAL::edge_external_index  ,surface)) 
+                  .edge_index_map  (boost::get(CGAL::edge_external_index  ,surface))
-                  .edge_is_border_map(constrains_map)
+                  .edge_is_constrained_map(constrained_edge_map)
             );
-  
+
-  std::cout << "\nFinished...\n" << r << " edges removed.\n" 
+  std::cout << "\nFinished...\n" << r << " edges removed.\n"
             << (surface.size_of_halfedges()/2) << " final edges.\n" ;
-        
+
   std::ofstream os( argc > 2 ? argv[2] : "out.off" ) ; os << surface ;
-  
+
-  return 0 ;      
+  return 0 ;
 }

Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_sharp_edges_constrained_polyhedron.cmd

@@ -0,0 +1 @@
+cube-meshed.off

Surface_mesh_simplification/examples/Surface_mesh_simplification/edge_collapse_sharp_edges_constrained_polyhedron.cpp

@@ -0,0 +1,173 @@
+#include <iostream>
+#include <fstream>
+
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Polyhedron_3.h>
+#include <CGAL/IO/Polyhedron_iostream.h>
+
+#include <CGAL/Surface_mesh_simplification/HalfedgeGraph_Polyhedron_3.h>
+#include <CGAL/Surface_mesh_simplification/edge_collapse.h>
+#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Constrained_placement_wrapper.h>
+#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Midpoint_placement.h>
+#include <CGAL/Unique_hash_map.h>
+#include <CGAL/Mesh_3/dihedral_angle_3.h>
+#include <CGAL/property_map.h>
+#include <cmath>
+
+typedef CGAL::Simple_cartesian<double> Kernel;
+typedef Kernel::Point_3 Point_3;
+typedef CGAL::Polyhedron_3<Kernel> Surface;
+typedef boost::graph_traits<Surface const>::edge_descriptor edge_descriptor;
+
+namespace SMS = CGAL::Surface_mesh_simplification ;
+
+
+typedef Surface::Facet_iterator Facet_iterator;
+typedef Surface::Halfedge_handle Halfedge_handle;
+typedef Surface::Halfedge_iterator Halfedge_iterator;
+
+
+//
+// BGL property map which indicates whether an edge is marked as non-removable
+//
+struct Constrained_edge_map : public boost::put_get_helper<bool,Constrained_edge_map>
+{
+  typedef boost::readable_property_map_tag      category;
+  typedef bool                                  value_type;
+  typedef bool                                  reference;
+  typedef edge_descriptor                       key_type;
+
+  Constrained_edge_map(const CGAL::Unique_hash_map<key_type,bool>& aConstraints)
+    : mConstraints(aConstraints) {}
+
+  reference operator[](key_type const& e) const { return  is_constrained(e); }
+
+  bool is_constrained( key_type const& e ) const {
+    return mConstraints.is_defined(e) ? mConstraints[e] : false ; }
+
+private:
+  const CGAL::Unique_hash_map<key_type,bool>& mConstraints;
+};
+
+//
+// A stop predicate that never says to stop.
+//
+struct No_stop_predicate
+{
+  typedef Surface ECM;
+  typedef double FT;
+  typedef boost::graph_traits<ECM>::edges_size_type size_type;
+  typedef SMS::Edge_profile<Surface> Profile;
+
+  bool operator()( FT const&, Profile const&, size_type, size_type) const
+  {
+    return false;
+  }
+};
+
+
+int main( int argc, char** argv )
+{
+  CGAL::Unique_hash_map<edge_descriptor,bool> constraint_hmap(false);
+
+  Surface surface;
+
+  if (argc!=2){
+    std::cerr<< "Usage: " << argv[0] << " input.off\n";
+    return 1;
+  }
+
+  std::ifstream is(argv[1]);
+  if(!is){
+    std::cerr<< "Filename provided is invalid\n";
+    return 1;
+  }
+
+  is >> surface ;
+
+  No_stop_predicate stop;
+
+  Constrained_edge_map constraints_map(constraint_hmap);
+  SMS::Constrained_placement_wrapper<SMS::Midpoint_placement<Surface>,
+                                     Constrained_edge_map >
+    placement(constraints_map);
+
+  // map used to check that constrained_edges and the points of its vertices
+  // are preserved at the end of the simplification
+  // Warning: the computation of the diedral angle is only an approximation and can
+  //          be far from the real value and could influence the detection of sharp
+  //          edges after the simplification
+  std::map<Surface::Halfedge_handle,std::pair<Point_3, Point_3> >constrained_edges;
+  std::size_t nb_sharp_edges=0;
+
+  // detect sharp edges
+  std::ofstream cst_output("constrained_edges.cgal");
+  for(Surface::Edge_iterator eb = surface.edges_begin(), ee = surface.edges_end() ; eb != ee ; ++eb )
+  {
+    if ( eb->is_border_edge() ){
+      ++nb_sharp_edges;
+      constraint_hmap[eb]=true;
+      constraint_hmap[eb->opposite()]=true;
+      constrained_edges[eb]=std::make_pair( eb->opposite()->vertex()->point(),
+                                            eb->vertex()->point() );
+    }
+    else{
+      double angle = CGAL::Mesh_3::dihedral_angle(
+        eb->opposite()->vertex()->point(),
+        eb->vertex()->point(),
+        eb->next()->vertex()->point(),
+        eb->opposite()->next()->vertex()->point() );
+      if ( std::abs(angle)<100 ){
+        ++nb_sharp_edges;
+        constraint_hmap[eb]=true;
+        constraint_hmap[eb->opposite()]=true;
+        constrained_edges[eb]=std::make_pair( eb->opposite()->vertex()->point(),
+                                              eb->vertex()->point() );
+        cst_output << "2 " << eb->opposite()->vertex()->point() << " "
+                           << " "  << eb->vertex()->point() << "\n";
+      }
+    }
+  }
+  cst_output.close();
+
+  int r
+  = SMS::edge_collapse(surface
+                       ,stop
+                       ,CGAL::vertex_index_map(boost::get(CGAL::vertex_external_index,surface))
+                       .edge_index_map  (boost::get(CGAL::edge_external_index  ,surface))
+                       .edge_is_constrained_map(constraints_map)
+                       .get_placement(placement)
+   );
+
+  std::cout << "\nFinished...\n" << r << " edges removed.\n"
+  << (surface.size_of_halfedges()/2) << " final edges.\n" ;
+  std::ofstream os(argc > 2 ? argv[2] : "out.off") ; os << surface ;
+
+  std::cout  << "Checking sharped edges were preserved...\n";
+  // check sharp edges were preserved
+  for(Surface::Edge_iterator eb = surface.edges_begin(), ee = surface.edges_end() ; eb != ee ; ++eb )
+  {
+    if ( eb->is_border_edge() ){
+      --nb_sharp_edges;
+      assert(
+        constrained_edges[eb]==std::make_pair( eb->opposite()->vertex()->point(),
+                                               eb->vertex()->point() ) );
+    }
+    else{
+      double angle = CGAL::Mesh_3::dihedral_angle(
+        eb->opposite()->vertex()->point(),
+        eb->vertex()->point(),
+        eb->next()->vertex()->point(),
+        eb->opposite()->next()->vertex()->point() );
+      if ( std::abs(angle)<100 ){
+        ++nb_sharp_edges;
+      assert(
+        constrained_edges[eb]==std::make_pair( eb->opposite()->vertex()->point(),
+                                               eb->vertex()->point() ) );
+      }
+    }
+  }
+  std::cout  << "OK\n";
+
+  return 0;
+}