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#include <CGAL/Simple_cartesian.h>
#include <CGAL/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/Edge_count_stop_predicate.h>
#include <CGAL/Unique_hash_map.h>
#include <CGAL/property_map.h>
#include <cmath>
#include <iostream>
#include <fstream>
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
{
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)
{}
value_type operator[](const key_type& e) const { return is_constrained(e); }
friend inline value_type get(const Constrained_edge_map& m, const key_type& k) { return m[k]; }
bool is_constrained(const key_type& 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)
{
Surface_mesh surface_mesh;
const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/cube-meshed.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;
}
CGAL::Unique_hash_map<edge_descriptor, bool> constraint_hmap(false);
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.polylines.txt");
for(edge_descriptor ed : edges(surface_mesh))
{
halfedge_descriptor hd = halfedge(ed, surface_mesh);
if(is_border(ed, surface_mesh))
{
std::cerr << "border" << std::endl;
++nb_sharp_edges;
constraint_hmap[ed] = true;
constrained_edges[ed] = std::make_pair(point(source(hd, surface_mesh), surface_mesh),
point(target(hd, surface_mesh), surface_mesh));
}
else
{
double angle = CGAL::approximate_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[ed] = true;
Point_3 p = point(source(hd, surface_mesh), surface_mesh);
Point_3 q = point(target(hd, surface_mesh), surface_mesh);
constrained_edges[ed] = 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::Edge_count_stop_predicate<Surface_mesh> stop(0);
std::cout << "Collapsing as many non-sharp 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(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(edge_descriptor ed : edges(surface_mesh))
{
halfedge_descriptor hd = halfedge(ed, surface_mesh);
if(is_border(ed, surface_mesh))
{
--nb_sharp_edges;
assert(constrained_edges[ed] == std::make_pair(point(source(hd, surface_mesh), surface_mesh),
point(target(hd, surface_mesh), surface_mesh)));
}
else
{
double angle = approximate_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[ed] == std::make_pair(point(source(hd, surface_mesh), surface_mesh),
point(target(hd, surface_mesh), surface_mesh)));
}
}
}
std::cout << "OK\n";
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 EXIT_FAILURE;
}
return EXIT_SUCCESS;
}
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