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CGAL 4.8 - 2D Generalized Barycentric Coordinates

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Barycentric_coordinates_2/Terrain_height_modeling.cpp
#include <CGAL/Delaunay_mesher_2.h>
#include <CGAL/Interpolation_traits_2.h>
#include <CGAL/Projection_traits_xy_3.h>
#include <CGAL/interpolation_functions.h>
#include <CGAL/Delaunay_mesh_face_base_2.h>
#include <CGAL/Delaunay_mesh_size_criteria_2.h>
#include <CGAL/Constrained_Delaunay_triangulation_2.h>
#include <CGAL/Barycentric_coordinates_2/Mean_value_2.h>
#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Barycentric_coordinates_2/Generalized_barycentric_coordinates_2.h>
// Some convenient typedefs.
// General.
typedef CGAL::Exact_predicates_inexact_constructions_kernel Kernel;
typedef CGAL::Projection_traits_xy_3<Kernel> Projection;
typedef Projection::FT Scalar;
typedef Projection::Point_2 Point;
typedef std::vector<Scalar> Scalar_vector;
typedef std::vector<Point> Point_vector;
// Coordinates related.
typedef CGAL::Barycentric_coordinates::Mean_value_2<Projection> Mean_value;
typedef CGAL::Barycentric_coordinates::Generalized_barycentric_coordinates_2<Mean_value, Projection> Mean_value_coordinates;
// Triangulation related.
typedef CGAL::Delaunay_mesh_face_base_2<Projection> Face_base;
typedef CGAL::Triangulation_vertex_base_2<Projection> Vertex_base;
typedef CGAL::Triangulation_data_structure_2<Vertex_base, Face_base> TDS;
typedef CGAL::Constrained_Delaunay_triangulation_2<Projection, TDS> CDT;
typedef CGAL::Delaunay_mesh_size_criteria_2<CDT> Criteria;
typedef CGAL::Delaunay_mesher_2<CDT, Criteria> Mesher;
typedef CDT::Finite_vertices_iterator Vertex_iterator;
typedef CDT::Vertex_handle Vertex_handle;
// Interpolation related.
typedef CGAL::Interpolation_traits_2<Projection> Interpolation_traits;
typedef CGAL::Data_access< std::map<Point, Scalar, Projection::Less_xy_2 > > Value_access;
// STD.
using std::cout; using std::endl; using std::string;
int main()
{
// Construct a polygon bounding a piece of three-dimensional terrain.
// Note that z-coordinate of each vertex represents the height function.
// Projection in 2D is done automatically by the Projection traits class.
const int number_of_vertices = 50;
Point_vector vertices(number_of_vertices);
vertices[0] = Point(0.03, 0.05, 0.000); vertices[1] = Point(0.07, 0.04, 10.00); vertices[2] = Point(0.10, 0.04, 20.00);
vertices[3] = Point(0.14, 0.04, 30.00); vertices[4] = Point(0.17, 0.07, 40.00); vertices[5] = Point(0.19, 0.09, 50.00);
vertices[6] = Point(0.22, 0.11, 60.00); vertices[7] = Point(0.25, 0.11, 70.00); vertices[8] = Point(0.27, 0.10, 80.00);
vertices[9] = Point(0.30, 0.07, 90.00); vertices[10] = Point(0.31, 0.04, 100.0); vertices[11] = Point(0.34, 0.03, 110.0);
vertices[12] = Point(0.37, 0.02, 120.0); vertices[13] = Point(0.40, 0.03, 130.0); vertices[14] = Point(0.42, 0.04, 140.0);
vertices[15] = Point(0.44, 0.07, 150.0); vertices[16] = Point(0.45, 0.10, 160.0); vertices[17] = Point(0.46, 0.13, 170.0);
vertices[18] = Point(0.46, 0.19, 180.0); vertices[19] = Point(0.47, 0.26, 190.0); vertices[20] = Point(0.47, 0.31, 200.0);
vertices[21] = Point(0.47, 0.35, 210.0); vertices[22] = Point(0.45, 0.37, 220.0); vertices[23] = Point(0.41, 0.38, 230.0);
vertices[24] = Point(0.38, 0.37, 240.0); vertices[25] = Point(0.35, 0.36, 250.0); vertices[26] = Point(0.32, 0.35, 260.0);
vertices[27] = Point(0.30, 0.37, 270.0); vertices[28] = Point(0.28, 0.39, 280.0); vertices[29] = Point(0.25, 0.40, 290.0);
vertices[30] = Point(0.23, 0.39, 300.0); vertices[31] = Point(0.21, 0.37, 310.0); vertices[32] = Point(0.21, 0.34, 320.0);
vertices[33] = Point(0.23, 0.32, 330.0); vertices[34] = Point(0.24, 0.29, 340.0); vertices[35] = Point(0.27, 0.24, 350.0);
vertices[36] = Point(0.29, 0.21, 360.0); vertices[37] = Point(0.29, 0.18, 370.0); vertices[38] = Point(0.26, 0.16, 380.0);
vertices[39] = Point(0.24, 0.17, 390.0); vertices[40] = Point(0.23, 0.19, 400.0); vertices[41] = Point(0.24, 0.22, 410.0);
vertices[42] = Point(0.24, 0.25, 420.0); vertices[43] = Point(0.21, 0.26, 430.0); vertices[44] = Point(0.17, 0.26, 440.0);
vertices[45] = Point(0.12, 0.24, 450.0); vertices[46] = Point(0.07, 0.20, 460.0); vertices[47] = Point(0.03, 0.15, 470.0);
vertices[48] = Point(0.01, 0.10, 480.0); vertices[49] = Point(0.02, 0.07, 490.0);
// Mesh this polygon.
// Create a constrained Delaunay triangulation.
CDT cdt;
std::vector<Vertex_handle> vertex_handle(number_of_vertices);
// Insert vertices of the polygon as our initial point set.
for(int i = 0; i < number_of_vertices; ++i) vertex_handle[i] = cdt.insert(vertices[i]);
// Insert constraints - edges of the polygon - in order to mesh only the polygon's interior.
for(int i = 0; i < number_of_vertices; ++i) cdt.insert_constraint(vertex_handle[i], vertex_handle[(i + 1) % number_of_vertices]);
Mesher mesher(cdt);
// Set a criteria on how to mesh.
mesher.set_criteria(Criteria(0.01, 0.01));
// Mesh the polygon.
mesher.refine_mesh();
// Compute mean value coordinates and use them to interpolate data from the polygon's boundary to its interior.
// Associate each point with the corresponding function value and coordinates.
std::map<Point, Scalar, Projection::Less_xy_2> point_function_value;
std::vector< std::pair<Point, Scalar> > point_coordinates(number_of_vertices);
for(int i = 0; i < number_of_vertices; ++i)
point_function_value.insert(std::make_pair(vertices[i], vertices[i].z()));
// Create an instance of the class with mean value coordinates.
Mean_value_coordinates mean_value_coordinates(vertices.begin(), vertices.end());
// Store all new interior points with interpolated data here.
std::vector<Point> points(cdt.number_of_vertices());
cout << endl << "Result of the height interpolation: " << endl << endl;
// Compute coordinates and interpolate the boundary data to the polygon's interior.
int index = 0;
for(Vertex_iterator vertex_iterator = cdt.finite_vertices_begin(); vertex_iterator != cdt.finite_vertices_end(); ++vertex_iterator) {
Scalar_vector coordinates;
const Point &point = vertex_iterator->point();
mean_value_coordinates(point, std::back_inserter(coordinates));
for(int j = 0; j < number_of_vertices; ++j)
point_coordinates[j] = std::make_pair(vertices[j], coordinates[j]);
Scalar f = CGAL::linear_interpolation(point_coordinates.begin(), point_coordinates.end(), Scalar(1), Value_access(point_function_value));
points[index] = Point(point.x(), point.y(), f);
cout << "The interpolated height with index " << index << " is " << f << ";" << endl;
++index;
}
cout << endl;
return EXIT_SUCCESS;
}