diff --git a/Nef_S2/include/CGAL/Nef_S2/Sphere_geometry_OGL.h b/Nef_S2/include/CGAL/Nef_S2/Sphere_geometry_OGL.h
index e7904529787..fa177c9c0bc 100644
--- a/Nef_S2/include/CGAL/Nef_S2/Sphere_geometry_OGL.h
+++ b/Nef_S2/include/CGAL/Nef_S2/Sphere_geometry_OGL.h
@@ -71,6 +71,23 @@ VVector convert(const CGAL::Vector_3<R>& v)
                  CGAL::to_double(v.y()),
                  CGAL::to_double(v.z())); }
 
+template <typename R>
+VVector normalize_and_convert(const CGAL::Vector_3<R>& v)
+{
+  typename R::FT xa = CGAL::abs(v.x());
+  typename R::FT ya = CGAL::abs(v.y());
+  typename R::FT za = CGAL::abs(v.z());
+  typename R::FT m = (std::max)((std::max)(xa,ya),za);
+  if (m==0) {
+      return VVector(0,0,0);
+  } else {
+      double xd = CGAL::to_double(v.x()/m);
+      double yd = CGAL::to_double(v.y()/m);
+      double zd = CGAL::to_double(v.z()/m);
+      VVector u(xd,yd,zd);
+      return u / CGAL_NTS sqrt(u*u) ; // normalize
+  }
+}
 
 const double refinement_angle = 0.1;
 const double shrink_fac = 0.995;