\( \newcommand{\E}{\mathrm{E}} \) \( \newcommand{\A}{\mathrm{A}} \) \( \newcommand{\R}{\mathrm{R}} \) \( \newcommand{\N}{\mathrm{N}} \) \( \newcommand{\Q}{\mathrm{Q}} \) \( \newcommand{\Z}{\mathrm{Z}} \) \( \def\ccSum #1#2#3{ \sum_{#1}^{#2}{#3} } \def\ccProd #1#2#3{ \sum_{#1}^{#2}{#3} }\)
CGAL 5.0.2 - Triangulated Surface Mesh Simplification
Surface_mesh_simplification/edge_collapse_constrained_border_surface_mesh.cpp
#include <iostream>
#include <fstream>
#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 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;
//
// 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;
for(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.
(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.precision(17);
os << surface_mesh;
// now check!
for(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;
}