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#include <CGAL/Simple_cartesian.h>
#include <CGAL/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.h>
// Stop-condition policy
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Edge_count_stop_predicate.h>
#include <iostream>
#include <fstream>
#include <map>
typedef CGAL::Simple_cartesian<double> Kernel;
typedef Kernel::Point_3 Point_3;
typedef CGAL::Polyhedron_3<Kernel> Surface_mesh;
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 boost::graph_traits<Surface_mesh>::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 value_type get(const 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;
const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/mesh_with_border.off");
std::ifstream is(filename);
if(!is || !(is >> surface_mesh))
{
std::cerr << "Failed to read input mesh: " << filename << std::endl;
return EXIT_FAILURE;
}
if(!CGAL::is_triangle_mesh(surface_mesh))
{
std::cerr << "Input geometry is not triangulated." << std::endl;
return EXIT_FAILURE;
}
// map used to check that constrained_edges and the points of its vertices
// are preserved at the end of the simplification
std::map<Surface_mesh::Halfedge_handle, std::pair<Point_3, Point_3> >constrained_edges;
std::size_t nb_border_edges=0;
for(Surface_mesh::Halfedge_iterator hit=surface_mesh.halfedges_begin(),
hit_end=surface_mesh.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;
}
}
// Contract the surface mesh as much as possible
SMS::Edge_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.
// The index maps are needed because the vertices and edges
// of this surface mesh lack an "id()" field.
std::cout << "Collapsing as many edges of mesh: " << filename << " as possible..." << std::endl;
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(bem)
.get_placement(Placement(bem)));
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.precision(17);
os << surface_mesh;
// now check!
for(Surface_mesh::Halfedge_iterator hit=surface_mesh.halfedges_begin(),
hit_end=surface_mesh.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 EXIT_SUCCESS;
}
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