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/* This file is part of the Gudhi Library. The Gudhi library
* (Geometric Understanding in Higher Dimensions) is a generic C++
* library for computational topology.
*
* Author(s): David Salinas
*
* Copyright (C) 2014 INRIA Sophia Antipolis-M�diterran�e (France)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
#ifndef GARLAND_HECKBERT_H_
#define GARLAND_HECKBERT_H_
#include <gudhi/Point.h>
#include <gudhi/Edge_contraction.h>
#include <gudhi/Skeleton_blocker.h>
#include <gudhi/Off_reader.h>
#include <iostream>
#include "Garland_heckbert/Error_quadric.h"
struct Geometry_trait {
typedef Point_d Point;
};
/**
* The vertex stored in the complex contains a quadric.
*/
struct Garland_heckbert_traits
: public Gudhi::skeleton_blocker::Skeleton_blocker_simple_geometric_traits<Geometry_trait> {
public:
struct Garland_heckbert_vertex : public Simple_geometric_vertex {
Error_quadric<Geometry_trait::Point> quadric;
};
typedef Garland_heckbert_vertex Graph_vertex;
};
using Complex = Gudhi::skeleton_blocker::Skeleton_blocker_geometric_complex< Garland_heckbert_traits >;
using EdgeProfile = Gudhi::contraction::Edge_profile<Complex>;
using Complex_contractor = Gudhi::contraction::Skeleton_blocker_contractor<Complex>;
/**
* How the new vertex is placed after an edge collapse : here it is placed at
* the point minimizing the cost of the quadric.
*/
class GH_placement : public Gudhi::contraction::Placement_policy<EdgeProfile> {
Complex& complex_;
public:
typedef Gudhi::contraction::Placement_policy<EdgeProfile>::Placement_type Placement_type;
GH_placement(Complex& complex) : complex_(complex) { (void)complex_; }
Placement_type operator()(const EdgeProfile& profile) const override {
auto sum_quad(profile.v0().quadric);
sum_quad += profile.v1().quadric;
boost::optional<Point> min_quadric_pt(sum_quad.min_cost());
if (min_quadric_pt)
return Placement_type(*min_quadric_pt);
else
return profile.p0();
}
};
/**
* How much cost an edge collapse : here the costs is given by a quadric
* which expresses a squared distances with triangles planes.
*/
class GH_cost : public Gudhi::contraction::Cost_policy<EdgeProfile> {
Complex& complex_;
public:
typedef Gudhi::contraction::Cost_policy<EdgeProfile>::Cost_type Cost_type;
GH_cost(Complex& complex) : complex_(complex) { (void)complex_; }
Cost_type operator()(EdgeProfile const& profile, boost::optional<Point> const& new_point) const override {
Cost_type res;
if (new_point) {
auto sum_quad(profile.v0().quadric);
sum_quad += profile.v1().quadric;
res = sum_quad.cost(*new_point);
}
return res;
}
};
/**
* Visitor that is called at several moment.
* Here we initializes the quadrics of every vertex at the on_started call back
* and we update them when contracting an edge (the quadric become the sum of both quadrics).
*/
class GH_visitor : public Gudhi::contraction::Contraction_visitor<EdgeProfile> {
Complex& complex_;
public:
GH_visitor(Complex& complex) : complex_(complex) { (void)complex_; }
// Compute quadrics for every vertex v
// The quadric of v consists in the sum of quadric
// of every triangles passing through v weighted by its area
void on_started(Complex & complex) override {
for (auto v : complex.vertex_range()) {
auto & quadric_v(complex[v].quadric);
for (auto t : complex.triangle_range(v)) {
auto t_it = t.begin();
const auto& p0(complex.point(*t_it++));
const auto& p1(complex.point(*t_it++));
const auto& p2(complex.point(*t_it++));
quadric_v += Error_quadric<Point>(p0, p1, p2);
}
}
}
/**
* @brief Called when an edge is about to be contracted and replaced by a vertex whose position is *placement.
*/
void on_contracting(EdgeProfile const &profile, boost::optional< Point > placement)
override {
profile.v0().quadric += profile.v1().quadric;
}
};
int main(int argc, char *argv[]) {
if (argc != 4) {
std::cerr << "Usage " << argv[0] <<
" input.off output.off N to load the file input.off, contract N edges and save the result to output.off.\n";
return EXIT_FAILURE;
}
Complex complex;
typedef Complex::Vertex_handle Vertex_handle;
// load the points
Gudhi::skeleton_blocker::Skeleton_blocker_off_reader<Complex> off_reader(argv[1], complex);
if (!off_reader.is_valid()) {
std::cerr << "Unable to read file:" << argv[1] << std::endl;
return EXIT_FAILURE;
}
if (!complex.empty() && !(complex.point(Vertex_handle(0)).dimension() == 3)) {
std::cerr << "Only points of dimension 3 are supported." << std::endl;
return EXIT_FAILURE;
}
std::cout << "Load complex with " << complex.num_vertices() << " vertices" << std::endl;
int num_contractions = atoi(argv[3]);
// constructs the contractor object with Garland Heckbert policies.
Complex_contractor contractor(complex,
new GH_cost(complex),
new GH_placement(complex),
Gudhi::contraction::make_link_valid_contraction<EdgeProfile>(),
new GH_visitor(complex));
std::cout << "Contract " << num_contractions << " edges" << std::endl;
contractor.contract_edges(num_contractions);
std::cout << "Final complex has " <<
complex.num_vertices() << " vertices, " <<
complex.num_edges() << " edges and " <<
complex.num_triangles() << " triangles." << std::endl;
// write simplified complex
Gudhi::skeleton_blocker::Skeleton_blocker_off_writer<Complex> off_writer(argv[2], complex);
return EXIT_SUCCESS;
}
#endif // GARLAND_HECKBERT_H_
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