Merge pull request #5033 from janetournois/Heat_method-degenerate_faces-GF

Heat_method_3 - avoid degenerate faces

Heat_method_3/include/CGAL/Heat_method_3/Surface_mesh_geodesic_distances_3.h

@@ -35,6 +35,7 @@
 #include <set>
 
 namespace CGAL {
+
 namespace Heat_method_3 {
 
 /**
@@ -49,6 +50,12 @@ struct Direct
 struct Intrinsic_Delaunay
 {};
 
+namespace internal {
+
+  template<typename TriangleMesh, typename Traits>
+  bool has_degenerate_faces(const TriangleMesh& tm, const Traits& traits);
+}
+
 namespace internal {
 template <typename TriangleMesh,
           typename Traits,
@@ -478,6 +485,9 @@ public:
   template<class VertexDistanceMap>
   void estimate_geodesic_distances(VertexDistanceMap vdm)
   {
+    CGAL_precondition(
+      !CGAL::Heat_method_3::internal::has_degenerate_faces(triangle_mesh(), Traits()));
+
     if(is_empty(tm)){
       return;
     }
@@ -676,6 +686,32 @@ struct Idt_storage
   {}
 };
 
+template<typename TriangleMesh, typename Traits>
+bool has_degenerate_faces(const TriangleMesh& tm, const Traits& traits)
+{
+  typedef typename Traits::Point_3  Point;
+  typedef typename Traits::Vector_3 Vector_3;
+  typename Traits::Construct_vector_3
+    construct_vector = traits.construct_vector_3_object();
+  typename Traits::Compute_scalar_product_3
+    scalar_product = traits.compute_scalar_product_3_object();
+  typename Traits::Construct_cross_product_vector_3
+    cross_product = traits.construct_cross_product_vector_3_object();
+
+  typename boost::property_map< TriangleMesh, boost::vertex_point_t>::const_type
+    vpm = get(boost::vertex_point, tm);
+  for (typename boost::graph_traits<TriangleMesh>::face_descriptor f : faces(tm))
+  {
+    const Point p1 = get(vpm, target(halfedge(f, tm), tm));
+    const Point p2 = get(vpm, target(next(halfedge(f, tm), tm), tm));
+    const Point p3 = get(vpm, target(next(next(halfedge(f, tm), tm), tm), tm));
+    Vector_3 v = cross_product(construct_vector(p1, p2), construct_vector(p1, p3));
+    if(scalar_product(v, v) == 0.)
+      return true;
+  }
+  return false;
+}
+
 template <typename TriangleMesh,
           typename Traits,
           typename LA,
@@ -715,6 +751,9 @@ struct Base_helper<TriangleMesh, Traits, Intrinsic_Delaunay, LA, VertexPointMap>
   template <class VertexDistanceMap>
   void estimate_geodesic_distances(VertexDistanceMap vdm)
   {
+    CGAL_precondition(
+      !CGAL::Heat_method_3::internal::has_degenerate_faces(
+        this->m_idt.triangle_mesh(), Traits()));
     base().estimate_geodesic_distances(this->m_idt.vertex_distance_map(vdm));
   }
 };
@@ -730,6 +769,7 @@ struct Base_helper<TriangleMesh, Traits, Intrinsic_Delaunay, LA, VertexPointMap>
  * time after changes to the set of sources.
  *
  * \tparam TriangleMesh a triangulated surface mesh, model of `FaceListGraph` and `HalfedgeListGraph`
+ *                      with no degenerate faces
  * \tparam Mode must be `Intrinsic_Delaunay` to indicate that an intrinsic Delaunay triangulation is internally constructed
  *                              or `Direct` to indicate that the input mesh should be used as is.
  *                              If `Intrinsic_Delaunay`, then the type `TriangleMesh` must have an internal property for `vertex_point`
@@ -743,7 +783,6 @@ struct Base_helper<TriangleMesh, Traits, Intrinsic_Delaunay, LA, VertexPointMap>
  *         is used as default
  * \tparam Traits a model of `HeatMethodTraits_3`. The default is the Kernel of the value type
  *         of the vertex point map (extracted using `Kernel_traits`).
- *
  */
 template <typename TriangleMesh,
           typename Mode = Direct,
@@ -901,6 +940,7 @@ public:
    * \tparam VertexDistanceMap a property map model of `WritablePropertyMap`
    * with `vertex_descriptor` as key type and `double` as value type.
    * \param vdm the vertex distance map to be filled
+   * \pre the support triangle mesh does not have any degenerate faces
    * \warning The key type is `double` even when used with an exact kernel.
    **/
   template <class VertexDistanceMap>
@@ -921,6 +961,7 @@ public:
 /// \tparam Mode either the tag `Direct` or `Intrinsic_Delaunay`, which determines if the geodesic distance
 ///              is computed directly on the mesh or if the intrinsic Delaunay triangulation is applied first.
 ///              The default is `Intrinsic_Delaunay`.
+/// \pre `tm` does not have any degenerate faces
 /// \warning The return type is `double` even when used with an exact kernel.
 ///
 /// \sa `CGAL::Heat_method_3::Surface_mesh_geodesic_distances_3`
@@ -962,6 +1003,7 @@ estimate_geodesic_distances(const TriangleMesh& tm,
 /// \tparam Mode either the tag `Direct` or `Intrinsic_Delaunay`, which determines if the geodesic distance
 ///              is computed directly on the mesh or if the intrinsic Delaunay triangulation is applied first.
 ///              The default is `Intrinsic_Delaunay`.
+/// \pre `tm` does not have any degenerate faces
 /// \warning The return type is `double` even when used with an exact kernel.
 /// \sa `CGAL::Heat_method_3::Surface_mesh_geodesic_distances_3`
 template <typename TriangleMesh, typename VertexDistanceMap, typename VertexConstRange, typename Mode>