diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Sizing_field.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Sizing_field.h
index 3df70524feca..fc6b14a984f5 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Sizing_field.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Sizing_field.h
@@ -10,12 +10,13 @@
 //
 // Author(s)     : Jane Tournois
 
-#ifndef CGAL_SIZING_FIELD_H
-#define CGAL_SIZING_FIELD_H
+#ifndef CGAL_PMP_REMESHING_SIZING_FIELD_H
+#define CGAL_PMP_REMESHING_SIZING_FIELD_H
 
 #include <CGAL/license/Polygon_mesh_processing/meshing_hole_filling.h>
 
 #include <CGAL/Kernel_traits.h>
+#include <boost/optional.hpp>
 
 namespace CGAL
 {
@@ -38,13 +39,14 @@ class Sizing_field
   typedef typename K::FT                                        FT;
 
 public:
-  virtual bool is_too_long(const halfedge_descriptor& h, FT& sql) const = 0;
-  virtual bool is_too_long(const vertex_descriptor& va, const vertex_descriptor& vb) const = 0;
-  virtual bool is_too_short(const halfedge_descriptor& h, FT& sqlen) const = 0;
+  virtual boost::optional<FT> is_too_long(const halfedge_descriptor& h) const = 0;
+  virtual boost::optional<FT> is_too_long(const vertex_descriptor& va,
+                                          const vertex_descriptor& vb) const = 0;
+  virtual boost::optional<FT> is_too_short(const halfedge_descriptor& h) const = 0;
   virtual Point_3 split_placement(const halfedge_descriptor& h) const = 0;
 
 };
 
 }//end namespace CGAL
 
-#endif //CGAL_SIZING_FIELD_H
+#endif //CGAL_PMP_REMESHING_SIZING_FIELD_H
diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Uniform_sizing_field.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Uniform_sizing_field.h
index 7b00635ff543..8704c84ef117 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Uniform_sizing_field.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/Uniform_sizing_field.h
@@ -10,8 +10,8 @@
 //
 // Author(s)     : Jane Tournois
 
-#ifndef CGAL_UNIFORM_SIZING_FIELD_H
-#define CGAL_UNIFORM_SIZING_FIELD_H
+#ifndef CGAL_PMP_REMESHING_UNIFORM_SIZING_FIELD_H
+#define CGAL_PMP_REMESHING_UNIFORM_SIZING_FIELD_H
 
 #include <CGAL/license/Polygon_mesh_processing/meshing_hole_filling.h>
 
@@ -54,23 +54,32 @@ class Uniform_sizing_field : public CGAL::Sizing_field<PolygonMesh>
   }
 
 public:
-  bool is_too_long(const halfedge_descriptor& h, FT& sqlen) const
+  boost::optional<FT> is_too_long(const halfedge_descriptor& h) const
   {
-    sqlen = sqlength(h);
-    return sqlen > m_sq_long;
+    const FT sqlen = sqlength(h);
+    if(sqlen > m_sq_long)
+      return sqlen;
+    else
+      return boost::none;
   }
 
-  bool is_too_long(const vertex_descriptor& va,
-                   const vertex_descriptor& vb) const
+  boost::optional<FT> is_too_long(const vertex_descriptor& va,
+                                  const vertex_descriptor& vb) const
   {
-    FT sqlen = sqlength(va, vb);
-    return sqlen > m_sq_long;
+    const FT sqlen = sqlength(va, vb);
+    if (sqlen > m_sq_long)
+      return sqlen;
+    else
+      return boost::none;
   }
 
-  bool is_too_short(const halfedge_descriptor& h, FT& sqlen) const
+  boost::optional<FT> is_too_short(const halfedge_descriptor& h) const
   {
-    sqlen = sqlength(h);
-    return sqlen < m_sq_short;
+    const FT sqlen = sqlength(h);
+    if (sqlen < m_sq_long)
+      return sqlen;
+    else
+      return boost::none;
   }
 
   virtual Point_3 split_placement(const halfedge_descriptor& h) const
@@ -89,4 +98,4 @@ class Uniform_sizing_field : public CGAL::Sizing_field<PolygonMesh>
 
 }//end namespace CGAL
 
-#endif //CGAL_UNIFORM_SIZING_FIELD_H
+#endif //CGAL_PMP_REMESHING_UNIFORM_SIZING_FIELD_H
diff --git a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h
index b8c4abd7dc56..29890d0c55b4 100644
--- a/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h
+++ b/Polygon_mesh_processing/include/CGAL/Polygon_mesh_processing/internal/Isotropic_remeshing/remesh_impl.h
@@ -488,9 +488,9 @@ namespace internal {
       {
         if (!is_split_allowed(e))
           continue;
-        double sqlen;
-        if(sizing.is_too_long(halfedge(e, mesh_), sqlen))
-          long_edges.insert(long_edge(halfedge(e, mesh_), sqlen));
+        boost::optional<double> sqlen = sizing.is_too_long(halfedge(e, mesh_));
+        if(sqlen != boost::none)
+          long_edges.insert(long_edge(halfedge(e, mesh_), sqlen.get()));
       }
 
       //split long edges
@@ -537,11 +537,13 @@ namespace internal {
 
         //check sub-edges
         //if it was more than twice the "long" threshold, insert them
-        double sqlen_new;
-        if(sizing.is_too_long(hnew, sqlen_new))
-          long_edges.insert(long_edge(hnew,              sqlen_new));
-        if(sizing.is_too_long(next(hnew, mesh_), sqlen_new))
-          long_edges.insert(long_edge(next(hnew, mesh_), sqlen_new));
+        boost::optional<double> sqlen_new = sizing.is_too_long(hnew);
+        if(sqlen_new != boost::none)
+          long_edges.insert(long_edge(hnew, sqlen_new.get()));
+
+        sqlen_new = sizing.is_too_long(next(hnew, mesh_));
+        if (sqlen_new != boost::none)
+          long_edges.insert(long_edge(next(hnew, mesh_), sqlen_new.get()));
 
         //insert new edges to keep triangular faces, and update long_edges
         if (!is_on_border(hnew))
@@ -560,9 +562,9 @@ namespace internal {
 
           if (snew == PATCH)
           {
-            double sql;
-            if(sizing.is_too_long(hnew2, sql))
-              long_edges.insert(long_edge(hnew2, sql));
+            boost::optional<double> sql = sizing.is_too_long(hnew2);
+            if(sql != boost::none)
+              long_edges.insert(long_edge(hnew2, sql.get()));
           }
         }
 
@@ -583,9 +585,9 @@ namespace internal {
 
           if (snew == PATCH)
           {
-            double sql;
-            if (sizing.is_too_long(hnew2, sql))
-              long_edges.insert(long_edge(hnew2, sql));
+            boost::optional<double> sql = sizing.is_too_long(hnew2);
+            if (sql != boost::none)
+              long_edges.insert(long_edge(hnew2, sql.get()));
           }
         }
       }
@@ -628,10 +630,10 @@ namespace internal {
       Boost_bimap short_edges;
       for(edge_descriptor e : edges(mesh_))
       {
-        double sqlen;
-        if(  sizing.is_too_short(halfedge(e, mesh_), sqlen)
+        boost::optional<double> sqlen = sizing.is_too_short(halfedge(e, mesh_));
+        if(sqlen != boost::none
           && is_collapse_allowed(e, collapse_constraints))
-          short_edges.insert(short_edge(halfedge(e, mesh_), sqlen));
+          short_edges.insert(short_edge(halfedge(e, mesh_), sqlen.get()));
       }
 #ifdef CGAL_PMP_REMESHING_VERBOSE_PROGRESS
       std::cout << "done." << std::endl;
@@ -725,7 +727,8 @@ namespace internal {
         for(halfedge_descriptor ha : halfedges_around_target(va, mesh_))
         {
           vertex_descriptor va_i = source(ha, mesh_);
-          if (sizing.is_too_long(vb, va_i))
+          boost::optional<double> sqha = sizing.is_too_long(vb, va_i);
+          if (sqha != boost::none)
           {
             collapse_ok = false;
             break;
@@ -789,10 +792,10 @@ namespace internal {
             //insert new/remaining short edges
             for (halfedge_descriptor ht : halfedges_around_target(vkept, mesh_))
             {
-              double sqlen;
-              if (sizing.is_too_short(ht, sqlen)
+              boost::optional<double> sqlen = sizing.is_too_short(ht);
+              if (sqlen != boost::none
                 && is_collapse_allowed(edge(ht, mesh_), collapse_constraints))
-                short_edges.insert(short_edge(ht, sqlen));
+                short_edges.insert(short_edge(ht, sqlen.get()));
             }
           }
         }//end if(collapse_ok)
@@ -1703,9 +1706,9 @@ namespace internal {
             //insert new edges in 'short_edges'
             if (is_collapse_allowed(edge(hf, mesh_), collapse_constraints))
             {
-              double sqlen;
-              if (sizing.is_too_short(hf, sqlen))
-                short_edges.insert(typename Bimap::value_type(hf, sqlen));
+              boost::optional<double> sqlen = sizing.is_too_short(hf);
+              if (sqlen != boost::none)
+                short_edges.insert(typename Bimap::value_type(hf, sqlen.get()));
             }
 
             if(!is_border(hf, mesh_) &&