Fast_alpha_complex_from_off.cpp
#include <gudhi/Alpha_complex.h>
// to construct a simplex_tree from alpha complex
#include <gudhi/Simplex_tree.h>
#include <CGAL/Epick_d.h>
#include <iostream>
#include <string>
void usage(int nbArgs, char * const progName) {
std::cerr << "Error: Number of arguments (" << nbArgs << ") is not correct\n";
std::cerr << "Usage: " << progName << " filename.off alpha_square_max_value [ouput_file.txt]\n";
std::cerr << " i.e.: " << progName << " ../../data/points/alphacomplexdoc.off 60.0\n";
exit(-1); // ----- >>
}
int main(int argc, char **argv) {
if ((argc != 3) && (argc != 4)) usage(argc, (argv[0] - 1));
std::string off_file_name {argv[1]};
double alpha_square_max_value {atof(argv[2])};
// WARNING : CGAL::Epick_d is fast but not safe (unlike CGAL::Epeck_d)
// (i.e. when the points are on a grid)
using Fast_kernel = CGAL::Epick_d<CGAL::Dynamic_dimension_tag>;
// ----------------------------------------------------------------------------
// Init of an alpha complex from an OFF file
// ----------------------------------------------------------------------------
Gudhi::alpha_complex::Alpha_complex<Fast_kernel> alpha_complex_from_file(off_file_name);
std::streambuf* streambuffer;
std::ofstream ouput_file_stream;
if (argc == 4) {
ouput_file_stream.open(std::string(argv[3]));
streambuffer = ouput_file_stream.rdbuf();
} else {
streambuffer = std::clog.rdbuf();
}
if (alpha_complex_from_file.create_complex(simplex, alpha_square_max_value)) {
std::ostream output_stream(streambuffer);
// ----------------------------------------------------------------------------
// Display information about the alpha complex
// ----------------------------------------------------------------------------
output_stream << "Alpha complex is of dimension " << simplex.dimension() <<
" - " << simplex.num_simplices() << " simplices - " <<
simplex.num_vertices() << " vertices." << std::endl;
output_stream << "Iterator on alpha complex simplices in the filtration order, with [filtration value]:" <<
std::endl;
for (auto f_simplex : simplex.filtration_simplex_range()) {
output_stream << " ( ";
for (auto vertex : simplex.simplex_vertex_range(f_simplex)) {
output_stream << vertex << " ";
}
output_stream << ") -> " << "[" << simplex.filtration(f_simplex) << "] ";
output_stream << std::endl;
}
}
ouput_file_stream.close();
return 0;
}
Simplex Tree data structure for representing simplicial complexes.
Definition: Simplex_tree.h:79
Filtration_simplex_range const & filtration_simplex_range(Indexing_tag=Indexing_tag())
Returns a range over the simplices of the simplicial complex, in the order of the filtration.
Definition: Simplex_tree.h:271
Simplex_vertex_range simplex_vertex_range(Simplex_handle sh) const
Returns a range over the vertices of a simplex.
Definition: Simplex_tree.h:282
static Filtration_value filtration(Simplex_handle sh)
Returns the filtration value of a simplex.
Definition: Simplex_tree.h:535
size_t num_vertices() const
Returns the number of vertices in the complex.
Definition: Simplex_tree.h:572
int dimension(Simplex_handle sh)
Returns the dimension of a simplex.
Definition: Simplex_tree.h:600
size_t num_simplices()
returns the number of simplices in the simplex_tree.
Definition: Simplex_tree.h:578
Alpha complex data structure.
Definition: Alpha_complex.h:103