CGAL 6.1 - 2D Straight Skeleton and Polygon Offsetting

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Straight_skeleton_2/extrude_skeleton.cpp
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Exact_predicates_exact_constructions_kernel.h>
//#include <CGAL/Exact_predicates_exact_constructions_kernel_with_sqrt.h>
#include <CGAL/Surface_mesh.h>
#include <CGAL/draw_straight_skeleton_2.h>
#include <CGAL/draw_surface_mesh.h>
#include "CGAL/input_helpers.h" // polygon reading, random polygon with weights generation
#include <CGAL/extrude_skeleton.h>
#include <CGAL/IO/polygon_mesh_io.h>
#include <CGAL/Polygon_2.h>
#include <CGAL/Real_timer.h>
#include <CGAL/Random.h>
#include <iostream>
#include <unordered_map>
#include <vector>
#include <memory>
namespace SS = CGAL::CGAL_SS_i;
namespace PMP = CGAL::Polygon_mesh_processing;
// Kernel choice:
// EPICK: Robust and fast
// EPECK_with_sqrt: Exact and slow
// EPECK: More robust, and less slow than EPECK_with_sqrt
using K = CGAL::Exact_predicates_inexact_constructions_kernel;
// using K = CGAL::Exact_predicates_exact_constructions_kernel;
// using K = CGAL::Exact_predicates_exact_constructions_kernel_with_sqrt;
using FT = K::FT;
using Point_2 = K::Point_2;
using Segment_2 = K::Segment_2;
using Line_2 = K::Line_2;
using Point_3 = K::Point_3;
using Vector_3 = K::Vector_3;
using Polygon_2 = CGAL::Polygon_2<K>;
using Polygon_with_holes_2 = CGAL::Polygon_with_holes_2<K>;
using Straight_skeleton_2 = CGAL::Straight_skeleton_2<K>;
using Straight_skeleton_2_ptr = std::shared_ptr<Straight_skeleton_2>;
using Mesh = CGAL::Surface_mesh<Point_3>;
int main(int argc, char** argv)
{
std::cout.precision(17);
std::cerr.precision(17);
const int argc_check = argc - 1;
char* poly_filename = nullptr;
char* speeds_filename = nullptr;
FT height = FT{(std::numeric_limits<double>::max)()};
bool use_angles = false; // whether the input is SLS edge weights, or taper angles
bool flip_weights = false; // takes the opposite for weights, and the complement for angles
// below is only used for random weight generation
double min_weight = 1., max_weight = 10.;
int seed = CGAL::get_default_random().get_seed();
for(int i = 1; i < argc; ++i)
{
if(!strcmp("-h", argv[i]) || !strcmp("--help", argv[i]) || !strcmp("-?", argv[i]))
{
std::cout << "Usage: " << argv[0] << "[options].\n"
"Options:\n"
" -i <input_filename>: input polygon filename.\n"
" -t <value>: height. Must be non-zero.\n"
" -a <angles_filename>: angles. Format: one angle per line, a space to separate borders.\n"
" -w <weights_filename>: weights. Format: one weight per line, a space to separate borders.\n"
" Note: -w and -a are exclusive.\n"
<< std::endl;
return EXIT_FAILURE;
} else if(!strcmp("-i", argv[i]) && i < argc_check) {
poly_filename = argv[++i];
} else if(!strcmp("-w", argv[i])) {
if(speeds_filename != nullptr)
{
std::cerr << "Error: -w and -a are exclusive." << std::endl;
return EXIT_FAILURE;
}
speeds_filename = argv[++i];
use_angles = false;
} else if(!strcmp("-a", argv[i])) {
if(speeds_filename != nullptr)
{
std::cerr << "Error: -w and -a are exclusive." << std::endl;
return EXIT_FAILURE;
}
speeds_filename = argv[++i];
use_angles = true;
} else if(!strcmp("-t", argv[i]) && i < argc_check) {
height = std::stod(argv[++i]);
} else if(!strcmp("-mw", argv[i]) && i < argc_check) {
min_weight = std::stod(argv[++i]);
} else if(!strcmp("-Mw", argv[i]) && i < argc_check) {
max_weight = std::stod(argv[++i]);
} else if(!strcmp("-f", argv[i]) && i < argc) {
flip_weights = true;
} else if(!strcmp("-s", argv[i]) && i < argc_check) {
seed = std::stoi(argv[++i]);
}
}
if(CGAL::is_zero(height))
{
std::cerr << "Error: height must be non-zero" << std::endl;
return EXIT_FAILURE;
}
CGAL::Real_timer timer;
timer.start();
Polygon_with_holes_2 pwh;
if(poly_filename == nullptr)
{
pwh = generate_random_polygon<Polygon_with_holes_2>(seed);
}
else if(!read_input_polygon(poly_filename, pwh) || pwh.outer_boundary().is_empty())
{
std::cerr << "Error: failure during polygon read" << std::endl;
return EXIT_FAILURE;
}
#ifdef CGAL_SLS_OUTPUT_FILES
std::ofstream out_poly("input.dat");
out_poly.precision(17);
out_poly << pwh;
out_poly.close();
#endif
// read segment speeds (angles or weights)
std::vector<std::vector<FT> > speeds;
if(speeds_filename == nullptr)
generate_random_weights(pwh, min_weight, max_weight, seed, speeds);
else
read_segment_speeds(speeds_filename, speeds);
if(flip_weights)
{
if(use_angles)
{
for(auto& contour_speeds : speeds)
for(FT& a : contour_speeds)
a = 180 - a;
}
else
{
for(auto& contour_speeds : speeds)
for(FT& w : contour_speeds)
w = -w;
}
}
timer.stop();
std::cout << "Reading input(s) took " << timer.time() << " s." << std::endl;
// End of I/O, do some slope preprocessing and check the validity of the input(s)
// -----------------------------------------------------------------------------------------------
timer.reset();
timer.start();
Mesh sm;
if(use_angles)
CGAL::extrude_skeleton(pwh, sm, CGAL::parameters::angles(speeds).maximum_height(height));
else
CGAL::extrude_skeleton(pwh, sm, CGAL::parameters::weights(speeds).maximum_height(height));
timer.stop();
std::cout << "Extrusion computation took " << timer.time() << " s." << std::endl;
CGAL::draw(sm);
CGAL::IO::write_polygon_mesh("extruded_skeleton.off", sm, CGAL::parameters::stream_precision(17));
return EXIT_SUCCESS;
}
CGAL::Exact_predicates_inexact_constructions_kernel
CGAL::Polygon_2
CGAL::Polygon_with_holes_2
CGAL::Straight_skeleton_2
The class Straight_skeleton_2 provides a model for the StraightSkeleton_2 concept which is the class ...
Definition: Straight_skeleton_2.h:178
CGAL::is_zero
result_type is_zero(const NT &x)
CGAL::IO::write_polygon_mesh
bool write_polygon_mesh(const std::string &fname, Graph &g, const NamedParameters &np=parameters::default_values())
CGAL::draw
void draw(const PS2 &ps2, const GSOptions &gso)
CGAL::extrude_skeleton
bool extrude_skeleton(const Polygon &polygon, PolygonMesh &out, const NamedParameters &np=parameters::default_values())
constructs the straight skeleton-based extrusion of a polygon with holes.