add an example showing a bug in the incremental builder.

Polyhedron/test/Polyhedron/bug_polyhedron_incremental_builder_3.cpp

@@ -0,0 +1,100 @@
+#include <CGAL/Simple_cartesian.h>
+#include <CGAL/Polyhedron_3.h>
+#include <CGAL/Polyhedron_incremental_builder_3.h>
+#include <CGAL/IO/Polyhedron_iostream.h>
+#include <sstream>
+
+typedef CGAL::Simple_cartesian<double> K;
+typedef CGAL::Polyhedron_3<K> Polyhedron;
+typedef Polyhedron::HalfedgeDS HDS;
+typedef CGAL::Polyhedron_incremental_builder_3<HDS> Builder;
+typedef CGAL::HalfedgeDS_decorator<HDS> Decorator;
+typedef HDS::Vertex::Base VBase;
+struct Appender : public CGAL::Modifier_base<HDS>
+{
+  void operator()(HDS& hds)
+  {
+    Builder B(hds);
+    B.begin_surface(1,1,4,Builder::ABSOLUTE_INDEXING);
+    B.add_vertex( K::Point_3(2,2,0) );
+    B.begin_facet();
+    B.add_vertex_to_facet(3);
+    B.add_vertex_to_facet(4);
+    B.add_vertex_to_facet(6);
+    B.end_facet();
+    B.end_surface();
+  }
+};
+
+/*!
+We start with this configuration:
+  0---3---4
+  |\  |\  |
+  | \ | \ |
+  |  \|  \|
+  1---2---5
+
+Then we update a the halfedge pointer of vertices
+3 and 4 so that the halfedges are on the boundary.
+We append a new facet to get the following:
+          6
+         /|
+        / |
+       /  |
+  0---3---4
+  |\  |\  |
+  | \ | \ |
+  |  \|  \|
+  1---2---5
+*/
+
+int main()
+{
+  std::stringstream ss;
+  ss << "\
+OFF\n6 4 0\n\
+0 1 0\n\
+0 0 0\n\
+1 0 0\n\
+1 1 0\n\
+2 1 0\n\
+2 0 0\n\
+3 0 1 2\n\
+3 0 2 3\n\
+3 2 5 3\n\
+3 5 4 3\n";
+
+  Polyhedron P;
+  ss >> P;
+
+  assert( P.size_of_vertices() == 6);
+  assert( P.size_of_facets() == 4);
+  assert( P.is_valid() );
+
+  //consider vertex 3 and set its halfedge to be on the border
+  Polyhedron::Vertex_iterator vit=P.vertices_begin();
+  std::advance(vit, 3);
+  assert( vit->point() == K::Point_3(1, 1, 0) );
+  Polyhedron::Halfedge_handle h=vit->halfedge();
+  while ( !h->is_border() )
+    h=h->next()->opposite();
+  vit->VBase::set_halfedge(h);
+  assert( vit->halfedge()->vertex() == vit );
+
+  //consider vertex 4 and set its halfedge to be on the border
+  ++vit;
+  assert( vit->point() == K::Point_3(2, 1, 0) );
+  h=vit->halfedge();
+  while ( !h->is_border() )
+    h=h->next()->opposite();
+  vit->VBase::set_halfedge(h);
+  assert( vit->halfedge()->vertex() == vit );
+
+  //try to append a facet
+  Appender modifier;
+  P.delegate(modifier);
+
+  assert( P.size_of_vertices() == 7);
+  assert( P.size_of_facets() == 5);
+  assert( P.is_valid() );
+}