- Add new example program : example_find_conflicts.C

Packages/Triangulation_3/examples/Triangulation_3/README

@@ -1,5 +1,5 @@
 
-------- example_simple -------------------------------------------------
+------- example_simple ---------------------------------------
 
 This example shows the incremental construction of a 3D triangulation, 
 the location of a point, and how to manipulate elementary operations
@@ -8,23 +8,32 @@ CGAL for the Triangulation_3 class.
 
 --------------------------------------------------------------
 
-------- example_color -------------------------------------------------
+------- example_color ----------------------------------------
 
 This example shows how the user can plug his own vertex base in a
 triangulation.
 
 --------------------------------------------------------------
 
-------- example_hierarchy -------------------------------------------------
+------- example_hierarchy ------------------------------------
 
 This example shows the use of the hierarchy to speed up the 
 construction of a Delaunay triangulation. 
 
 --------------------------------------------------------------
 
-------- example_tds -------------------------------------------------
+------- example_tds ------------------------------------------
 
 Shows how to construct a 3D triangulation data structure by 
 inserting vertices.
 
 --------------------------------------------------------------
+
+------- example_find_conflicts -------------------------------
+
+Illustrates how the insertion process of points in a Delaunay
+triangulation can be decomposed in order to give access to the
+cells in conflict (those which would be destroyed by the insertion
+of a point) prior to deciding to do the actual insertion or not.
+
+--------------------------------------------------------------

Packages/Triangulation_3/examples/Triangulation_3/example_find_conflicts.C

@@ -0,0 +1,61 @@
+// Triangulation_3/example_find_conflicts.C
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Filtered_kernel.h>
+#include <CGAL/Delaunay_triangulation_3.h>
+#include <CGAL/point_generators_3.h>
+
+#include <vector>
+#include <cassert>
+
+struct K : CGAL::Filtered_kernel<CGAL::Simple_cartesian<double> > {};
+
+typedef CGAL::Delaunay_triangulation_3<K>        Delaunay;
+typedef Delaunay::Point                          Point;
+typedef Delaunay::Cell_handle                    Cell_handle;
+typedef Delaunay::Facet                          Facet;
+
+int main()
+{
+  Delaunay T;
+  CGAL::Random_points_in_sphere_3<Point> rnd;
+
+  // First, make sure the triangulation is 3D.
+  T.insert(Point(0,0,0));
+  T.insert(Point(1,0,0));
+  T.insert(Point(0,1,0));
+  T.insert(Point(0,0,1));
+
+  assert(T.dimension() == 3);
+
+  // Inserts 100 random points if and only if their insertion
+  // in the Delaunay tetrahedralization would conflict with
+  // an even number of cells.
+  for (int i = 0; i != 100; ++i) {
+    Point p = *rnd++;
+
+    // Locate the point
+    Delaunay::Locate_type lt;
+    int li, lj;
+    Cell_handle c = T.locate(p, lt, li, lj);
+    if (lt == Delaunay::VERTEX)
+      continue; // Point already exists
+
+    // Get the cells that conflict with p in a vector V,
+    // and a facet on the boundary of this hole in f.
+    std::vector<Cell_handle> V;
+    Facet f;
+
+    T.find_conflicts(p, c,
+                     CGAL::Oneset_iterator<Facet>(f), // Get one boundary facet
+                     std::back_inserter(V),           // Conflict cells in V
+                     CGAL::Emptyset_iterator());      // Drop internal facets
+
+    if ((V.size() & 1) == 0)  // Even number of conflict cells ?
+      T.insert_in_hole(p, V.begin(), V.end(), f.first, f.second);
+  }
+
+  std::cout << "Final triangulation has " << T.number_of_vertices()
+            << " vertices." << std::endl;
+
+  return 0;
+}