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#include <CGAL/Simple_cartesian.h>
#include <CGAL/Surface_mesh.h>
// Simplification function
#include <CGAL/Surface_mesh_simplification/edge_collapse.h>
// Visitor base
#include <CGAL/Surface_mesh_simplification/Edge_collapse_visitor_base.h>
// Stop-condition policy
#include <CGAL/Surface_mesh_simplification/Policies/Edge_collapse/Edge_count_ratio_stop_predicate.h>
#include <iostream>
#include <fstream>
typedef CGAL::Simple_cartesian<double> Kernel;
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>::vertex_descriptor vertex_descriptor;
namespace SMS = CGAL::Surface_mesh_simplification;
typedef SMS::Edge_profile<Surface_mesh> Profile;
// The following is a Visitor that keeps track of the simplification process.
// In this example the progress is printed real-time and a few statistics are
// recorded (and printed in the end).
//
struct Stats
{
std::size_t collected = 0;
std::size_t processed = 0;
std::size_t collapsed = 0;
std::size_t non_collapsable = 0;
std::size_t cost_uncomputable = 0;
std::size_t placement_uncomputable = 0;
};
struct My_visitor : SMS::Edge_collapse_visitor_base<Surface_mesh>
{
My_visitor(Stats* s) : stats(s) {}
// Called during the collecting phase for each edge collected.
void OnCollected(const Profile&, const std::optional<double>&)
{
++(stats->collected);
std::cerr << "\rEdges collected: " << stats->collected << std::flush;
}
// Called during the processing phase for each edge selected.
// If cost is absent the edge won't be collapsed.
void OnSelected(const Profile&,
std::optional<double> cost,
std::size_t initial,
std::size_t current)
{
++(stats->processed);
if(!cost)
++(stats->cost_uncomputable);
if(current == initial)
std::cerr << "\n" << std::flush;
std::cerr << "\r" << current << std::flush;
}
// Called during the processing phase for each edge being collapsed.
// If placement is absent the edge is left uncollapsed.
void OnCollapsing(const Profile&,
std::optional<Point> placement)
{
if(!placement)
++(stats->placement_uncomputable);
}
// Called for each edge which failed the so called link-condition,
// that is, which cannot be collapsed because doing so would
// turn the surface mesh into a non-manifold.
void OnNonCollapsable(const Profile&)
{
++(stats->non_collapsable);
}
// Called after each edge has been collapsed
void OnCollapsed(const Profile&, vertex_descriptor)
{
++(stats->collapsed);
}
Stats* stats;
};
int main(int argc, char** argv)
{
Surface_mesh surface_mesh;
const std::string filename = (argc > 1) ? argv[1] : CGAL::data_file_path("meshes/small_cube.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;
}
// In this example, the simplification stops when the number of undirected edges
// drops below xx% of the initial count
const double ratio = (argc > 2) ? std::stod(argv[2]) : 0.1;
SMS::Edge_count_ratio_stop_predicate<Surface_mesh> stop(ratio);
Stats stats;
My_visitor vis(&stats);
// The index maps are not explicitelty passed as in the previous
// example because the surface mesh items have a proper id() field.
// On the other hand, we pass here explicit cost and placement
// function which differ from the default policies, omitted in
// the previous example.
int r = SMS::edge_collapse(surface_mesh, stop, CGAL::parameters::visitor(vis));
std::cout << "\nEdges collected: " << stats.collected
<< "\nEdges processed: " << stats.processed
<< "\nEdges collapsed: " << stats.collapsed
<< std::endl
<< "\nEdges not collapsed due to topological constraints: " << stats.non_collapsable
<< "\nEdge not collapsed due to cost computation constraints: " << stats.cost_uncomputable
<< "\nEdge not collapsed due to placement computation constraints: " << stats.placement_uncomputable
<< std::endl;
std::cout << "\nFinished!\n" << r << " edges removed.\n"
<< surface_mesh.number_of_edges() << " final edges.\n";
CGAL::IO::write_polygon_mesh((argc > 3) ? argv[3] : "out.off", surface_mesh, CGAL::parameters::stream_precision(17));
return EXIT_SUCCESS;
}
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