diff --git a/Heat_method_3/doc/Heat_method_3/Concepts/HeatMethodTraits_3.h b/Heat_method_3/doc/Heat_method_3/Concepts/HeatMethodTraits_3.h
index 4979d087520..fcb821be832 100644
--- a/Heat_method_3/doc/Heat_method_3/Concepts/HeatMethodTraits_3.h
+++ b/Heat_method_3/doc/Heat_method_3/Concepts/HeatMethodTraits_3.h
@@ -19,20 +19,52 @@ public:
 /// \name Types
 /// @{
 
-  /// The 3D point type.
+  // The number type. It must be `CopyConstructible` and `DefaultConstructible`,
+  // and be constructible from `double`.
+  typdef unspecified_type FT;
+  
+  /// The 3D point type. It must be `CopyConstructible` and `DefaultConstructible`,
+  /// and have a constructor with three parameters of a type constructibe from `double`.
   typedef unspecified_type Point_3;
   
-  /// The 3D vector type.
+  /// The 3D vector type.  It must be `CopyConstructible` and `DefaultConstructible`,
+  /// and have a constructor with three parameters of a type constructibe from `double`.
   typedef unspecified_type Vector_3;
-  
+
+  /// Functor with operator: `Vector_3 operator()(Point_3 from, Point_3 to) const`.
   typedef unspecified_type Construct_vector_3;
+
+  ///  Functor with operator: `Vector_3 operator()(Vector_3 v, Vector_3 w) const`.
   typedef unspecified_type Construct_sum_of_vectors_3;
+  
+  ///  Functor with operator: `Vector_3 operator()(Vector_3 v, double d) const`.
   typedef unspecified_type Construct_scaled_vector_3;
+  
+  ///  Functor with operator: `Vector_3 operator()(Vector_3 v, Vector_3 w) const`.
   typedef unspecified_type Construct_cross_product_vector_3;
+  
+  ///  Functor with operator: `double operator()(Vector_3 v, Vector_3 w) const`.
   typedef unspecified_type Compute_scalar_product_3;
+  
+  ///  Functor with operator: `double operator()(Point_3 p, Point_3 q) const`.
   typedef unspecified_type Compute_squared_distance_3;
   
+  
 /// @}
 
+/*! \name Operations 
+For each of the above function object types, 
+`Func_obj_type`, a function must exist with the name 
+`func_obj_type_object` that creates an instance of the function or 
+predicate object type. For example: 
+*/
+/// @{
+
+/*!
+
+*/ 
+Construct_vector_3 construct_vector_3_object(); 
+
+/// @}
 
 };
diff --git a/Heat_method_3/include/CGAL/Heat_method_3/Surface_mesh_geodesic_distances_3.h b/Heat_method_3/include/CGAL/Heat_method_3/Surface_mesh_geodesic_distances_3.h
index ca2af279354..9e5eafb2b14 100644
--- a/Heat_method_3/include/CGAL/Heat_method_3/Surface_mesh_geodesic_distances_3.h
+++ b/Heat_method_3/include/CGAL/Heat_method_3/Surface_mesh_geodesic_distances_3.h
@@ -740,27 +740,26 @@ struct Base_helper<TriangleMesh, Traits, Intrinsic_Delaunay, LA, VertexPointMap>
  * time after changes of the set of sources.
  *
  * \tparam TriangleMesh a triangulated surface mesh, model of `FaceListGraph` and `HalfedgeListGraph`
- * \tparam Traits a model of HeatMethodTraits_3
- * \tparam Mode indicates if an intrinsic Delaunay triangulation should be internally constructed (`Intrinsic_Delaunay`)
- *                              or if the input mesh should be used as is (`Direct`).
+ * \tparam Mode must be `Intrinsic_Delaunay` to indicatethat an intrinsic Delaunay triangulation is internally constructed ()
+ *                              or `Direct`to indicate that the input mesh should be used as is.
  *                              If `Intrinsic_Delaunay` the type `TriangleMesh` must have an internal property for `vertex_point`
  *                              and its value type must be the same as the value type of `VertexPointMap`.
- * \tparam LA a model of `SparseLinearAlgebraWithFactorTraits_d`.
-
  * \tparam VertexPointMap a model of `ReadablePropertyMap` with
  *        `boost::graph_traits<TriangleMesh>::%vertex_descriptor` as key and
  *        `Traits::Point_3` as value type.
  *        The default is `typename boost::property_map<TriangleMesh, vertex_point_t>::%type`.
+ * \tparam LA a model of `SparseLinearAlgebraWithFactorTraits_d`.
+ * \tparam Traits a model of `HeatMethodTraits_3`
  *
  */
 template <typename TriangleMesh,
           typename Mode = Direct,
+          typename VertexPointMap = typename boost::property_map< TriangleMesh, vertex_point_t>::const_type,
 #ifdef CGAL_EIGEN3_ENABLED
           typename LA = Eigen_solver_traits<Eigen::SimplicialLDLT<typename Eigen_sparse_matrix<double>::EigenType > >,
 #else
           typename LA = Default,
 #endif
-          typename VertexPointMap = typename boost::property_map< TriangleMesh, vertex_point_t>::const_type,
           typename Traits = typename Kernel_traits< typename boost::property_traits<VertexPointMap>::value_type>::Kernel >
 class Surface_mesh_geodesic_distances_3
 #ifndef DOXYGEN_RUNNING