CGAL 4.7 - Triangulated Surface Mesh Simplification: Surface_mesh_simplification/edge_collapse_constrain_sharp_edges.cpp

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CGAL 4.7 - Triangulated Surface Mesh Simplification

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Surface_mesh_simplification/edge_collapse_constrain_sharp_edges.cpp
#include <iostream>
#include <fstream>
#include <CGAL/Simple_cartesian.h>
#include <CGAL/Polyhedron_3.h>
#include <CGAL/IO/Polyhedron_iostream.h>
#include <CGAL/boost/graph/graph_traits_Polyhedron_3.h>
#include <CGAL/Surface_mesh_simplification/edge_collapse.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Constrained_placement.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Midpoint_placement.h>
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Count_stop_predicate.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_mesh;
typedef boost::graph_traits<Surface_mesh>::vertex_descriptor vertex_descriptor;
typedef boost::graph_traits<Surface_mesh>::halfedge_descriptor halfedge_descriptor;
typedef boost::graph_traits<Surface_mesh>::edge_descriptor edge_descriptor;
typedef boost::graph_traits<Surface_mesh>::edge_iterator edge_iterator;
namespace SMS = CGAL::Surface_mesh_simplification ;
//
// 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);
}
private:
const CGAL::Unique_hash_map<key_type,bool>& mConstraints;
};
bool is_border (edge_descriptor e, const Surface_mesh& sm)
{
return (face(halfedge(e,sm),sm) == boost::graph_traits<Surface_mesh>::null_face() )
|| (face( opposite(halfedge(e,sm),sm),sm) == boost::graph_traits<Surface_mesh>::null_face() );
}
Point_3 point(vertex_descriptor vd, const Surface_mesh& sm)
{
return get( CGAL::vertex_point, sm, vd);
}
int main( int argc, char** argv )
{
CGAL::Unique_hash_map<edge_descriptor,bool> constraint_hmap(false);
Surface_mesh surface_mesh;
if (argc < 2){
std::cerr<< "Usage: " << argv[0] << " input.off [out.off]\n";
return 1;
}
std::ifstream is(argv[1]);
if(!is){
std::cerr<< "Filename provided is invalid\n";
return 1;
}
is >> surface_mesh ;
Constrained_edge_map constraints_map(constraint_hmap);
SMS::Constrained_placement<SMS::Midpoint_placement<Surface_mesh>,
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 dihedral 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<edge_descriptor,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");
edge_iterator eb,ee;
for(boost::tie(eb,ee) = edges(surface_mesh); eb != ee ; ++eb )
{
halfedge_descriptor hd = halfedge(*eb,surface_mesh);
if ( is_border(*eb,surface_mesh) ){
std::cerr << "border" << std::endl;
++nb_sharp_edges;
constraint_hmap[*eb]=true;
constrained_edges[*eb]=std::make_pair(point(source(hd,surface_mesh),surface_mesh),
point(target(hd,surface_mesh),surface_mesh));
}
else{
double angle = CGAL::Mesh_3::dihedral_angle(point(target(opposite(hd,surface_mesh),surface_mesh),surface_mesh),
point(target(hd,surface_mesh),surface_mesh),
point(target( next(hd,surface_mesh),surface_mesh),surface_mesh),
point(target(next(opposite(hd,surface_mesh),surface_mesh),surface_mesh),surface_mesh));
if ( CGAL::abs(angle)<100 ){
++nb_sharp_edges;
constraint_hmap[*eb]=true;
Point_3 p = point(source(hd,surface_mesh),surface_mesh);
Point_3 q = point(target(hd,surface_mesh),surface_mesh);
constrained_edges[*eb]=std::make_pair(p,q);
cst_output << "2 " << p << " " << q << "\n";
}
}
}
cst_output.close();
std::cerr << "# sharp edges = " << nb_sharp_edges << std::endl;
// Contract the surface mesh as much as possible
SMS::Count_stop_predicate<Surface_mesh> stop(0);
int r
= SMS::edge_collapse(surface_mesh
,stop
,CGAL::parameters::vertex_index_map(get(CGAL::vertex_external_index, surface_mesh))
.halfedge_index_map(get(CGAL::halfedge_external_index, surface_mesh))
.edge_is_constrained_map(constraints_map)
.get_placement(placement)
);
std::cout << "\nFinished...\n" << r << " edges removed.\n"
<< num_edges(surface_mesh) << " final edges.\n" ;
std::ofstream os(argc > 2 ? argv[2] : "out.off") ; os << surface_mesh ;
std::cout << "Checking sharped edges were preserved...\n";
// check sharp edges were preserved
for(boost::tie(eb,ee) = edges(surface_mesh); eb != ee ; ++eb )
{
halfedge_descriptor hd = halfedge(*eb,surface_mesh);
if ( is_border(*eb,surface_mesh) ){
--nb_sharp_edges;
assert(
constrained_edges[*eb]==std::make_pair( point(source(hd,surface_mesh),surface_mesh),
point(target(hd,surface_mesh),surface_mesh)));
}
else{
double angle = CGAL::Mesh_3::dihedral_angle(point(target(opposite(hd,surface_mesh),surface_mesh),surface_mesh),
point(target(hd,surface_mesh),surface_mesh),
point(target(next(hd,surface_mesh),surface_mesh),surface_mesh),
point(target(next(opposite(hd,surface_mesh),surface_mesh),surface_mesh),surface_mesh));
if ( CGAL::abs(angle)<100 ){
--nb_sharp_edges;
assert(
constrained_edges[*eb]==std::make_pair( point(source(hd,surface_mesh),surface_mesh),
point(target(hd,surface_mesh),surface_mesh)));
}
}
}
std::cout << "OK\n";
std::cerr << "# sharp edges = " << nb_sharp_edges << std::endl;
std::cout << "Check that no removable edge has been forgotten..." << std::endl;
r = SMS::edge_collapse(surface_mesh
,stop
,CGAL::parameters::vertex_index_map(get(CGAL::vertex_external_index, surface_mesh))
.halfedge_index_map (get(CGAL::halfedge_external_index, surface_mesh))
.edge_is_constrained_map(constraints_map)
.get_placement(placement)
);
assert(r==0);
if ( r==0 )
std::cout << "OK\n";
else{
std::cout << "ERROR! " << r << " edges removed!\n";
return 1;
}
return 0;
}