Added an example of Alpha Shapes 3D with a regular periodic triangulation

Alpha_shapes_3/examples/Alpha_shapes_3/ex_weighted_periodic_alpha_shapes_3.cpp

@@ -0,0 +1,103 @@
+#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
+
+#include <CGAL/Alpha_shape_3.h>
+#include <CGAL/Periodic_3_regular_triangulation_traits_3.h>
+#include <CGAL/Periodic_3_regular_triangulation_3.h>
+
+#include <CGAL/Random.h>
+#include <CGAL/point_generators_3.h>
+
+#include <fstream>
+#include <iostream>
+
+
+// Traits
+typedef CGAL::Exact_predicates_inexact_constructions_kernel  K;
+typedef CGAL::Periodic_3_regular_triangulation_traits_3<K>   PK;
+
+// Vertex type
+typedef CGAL::Periodic_3_triangulation_ds_vertex_base_3<>    DsVb;
+typedef CGAL::Regular_triangulation_vertex_base_3<PK,DsVb>   Vb;
+typedef CGAL::Alpha_shape_vertex_base_3<PK,Vb>               AsVb;
+// Cell type
+typedef CGAL::Periodic_3_triangulation_ds_cell_base_3<>      DsCb;
+typedef CGAL::Regular_triangulation_cell_base_3<PK,DsCb>     Cb;
+typedef CGAL::Alpha_shape_cell_base_3<PK,Cb>                 AsCb;
+
+typedef CGAL::Triangulation_data_structure_3<AsVb,AsCb>      Tds;
+typedef CGAL::Periodic_3_regular_triangulation_3<PK,Tds>     P3RT3;
+typedef CGAL::Alpha_shape_3<P3RT3>                           Alpha_shape_3;
+
+typedef P3RT3::Bare_point                                    Bare_point;
+typedef P3RT3::Weighted_point                                Weighted_point;
+
+int main()
+{
+  typedef CGAL::Creator_uniform_3<double, Bare_point> Creator;
+  CGAL::Random random(8);
+  CGAL::Random_points_in_cube_3<Bare_point, Creator> in_cube(1, random);
+  std::vector<Weighted_point> pts;
+
+  // read input
+  std::ifstream is("./data/bunny_1000");
+  int n;
+  is >> n;
+  std::cout << "Reading " << n << " points " << std::endl;
+  Bare_point bp;
+  for( ; n>0 ; n--) {
+    is >> bp;
+    Weighted_point p(bp, 0.01 * random.get_double(0., 0.015625));
+    pts.push_back(p);
+  }
+
+/*
+  // Generating 1000 random points
+  for(int i=0; i<1000 ; i++) {
+    Weighted_point p(*in_cube++, random.get_double(0., 0.015625));
+//    Weighted_point p(*in_cube++, 0.);
+    std::cout << "inserting: " << i << " || " << p << std::endl;
+    pts.push_back(p);
+  }
+*/
+
+  // Define the periodic cube
+  P3RT3 prt(PK::Iso_cuboid_3(-0.1,0.,-0.1, 0.1,0.2,0.1));
+
+  // Heuristic for inserting large point sets (if pts is reasonably large)
+  prt.insert(pts.begin(), pts.end(), true);
+
+  // As prt won't be modified anymore switch to 1-sheeted cover if possible
+  if(prt.is_triangulation_in_1_sheet())
+  {
+    std::cout << "Switching to 1-sheeted covering" << std::endl;
+    prt.convert_to_1_sheeted_covering();
+  }
+
+  std::cout << "Periodic Regular computed." << std::endl;
+
+  // compute alpha shape
+  Alpha_shape_3 as(prt);
+  std::cout << "Alpha shape computed in REGULARIZED mode by default." << std::endl;
+
+   // find optimal alpha values
+  Alpha_shape_3::NT alpha_solid = as.find_alpha_solid();
+  Alpha_shape_3::Alpha_iterator opt = as.find_optimal_alpha(1);
+  std::cout << "Smallest alpha value to get a solid through data points is " << alpha_solid << std::endl;
+  std::cout << "Optimal alpha value to get one connected component is " << *opt << std::endl;
+  as.set_alpha(*opt);
+//  assert(as.number_of_solid_components() == 1);
+
+  CGAL::Geomview_stream gv(CGAL::Bbox_3(-0.1,0.,-0.1, 0.1,0.2,0.1));
+  gv.set_bg_color(CGAL::Color(0, 200, 200));
+  gv.clear();
+
+  gv << as;
+  gv.set_wired(true);
+  gv << as;
+
+  char ch;
+  std::cout << "Enter any character to quit" << std::endl;
+  std::cin >> ch;
+
+  return 0;
+}