normal vector doc

diff --git a/include/deal.II/grid/manifold.h b/include/deal.II/grid/manifold.h
index 6f0aa4b97c4d0e1f9eadba4a9d8d6a6bcc871400..b230690e74cd04cb0f0ade79d6b6d38404e9f4b0 100644 (file)
--- a/include/deal.II/grid/manifold.h
+++ b/include/deal.II/grid/manifold.h
@@ -548,7 +548,8 @@ public:
 
   /**
    * Return the normal vector to a face embedded in this manifold, at
-   * the point p. If p is not in fact on the surface, but only
+   * the point p. It is not required that the normals actually point
+   * outward. If p is not in fact on the surface, but only
    * close-by, try to return something reasonable, for example the
    * normal vector at the surface point closest to p.  (The point p
    * will in fact not normally lie on the actual surface, but rather