From: Wolfgang Bangerth <bangerth@colostate.edu>
Date: Fri, 4 Aug 2017 22:26:00 +0000 (-0600)
Subject: Update documentation in GridOut.
X-Git-Tag: v9.0.0-rc1~1358^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=3c85aaa685e8ea290b9cb74cab9d5d65eda7f3cb;p=dealii.git

Update documentation in GridOut.
---

diff --git a/include/deal.II/grid/grid_out.h b/include/deal.II/grid/grid_out.h
index 8547991e92..83ba798e3f 100644
--- a/include/deal.II/grid/grid_out.h
+++ b/include/deal.II/grid/grid_out.h
@@ -1074,6 +1074,20 @@ public:
 
   /**
    * Write triangulation in VTK format.
+   *
+   * Due to the way this function writes data to the output stream,
+   * the resulting output files correspond to a faithful representation
+   * of the mesh in that all cells are visible for visualization. However,
+   * the data is not in a format that allows reading this file in again
+   * through the GridIn class. This is because every vertex of the mesh is
+   * duplicated as many times as there are adjacent cells. In other words,
+   * every cell has its own, separate set of vertices that are at the
+   * same location as the vertices of other cells, but are separately
+   * numbered. If such a file is read in through the GridIn class, then
+   * that will result in a mesh that has the correct cells and vertex
+   * locations, but because the vertices are logically separate (though at
+   * the same locations) all cells are unconnected and have no neighbors
+   * across faces.
    */
   template <int dim, int spacedim>
   void write_vtk (const Triangulation<dim,spacedim> &tria,
@@ -1081,6 +1095,20 @@ public:
 
   /**
    * Write triangulation in VTU format.
+   *
+   * Due to the way this function writes data to the output stream,
+   * the resulting output files correspond to a faithful representation
+   * of the mesh in that all cells are visible for visualization. However,
+   * the data is not in a format that allows reading this file in again
+   * through the GridIn class. This is because every vertex of the mesh is
+   * duplicated as many times as there are adjacent cells. In other words,
+   * every cell has its own, separate set of vertices that are at the
+   * same location as the vertices of other cells, but are separately
+   * numbered. If such a file is read in through the GridIn class, then
+   * that will result in a mesh that has the correct cells and vertex
+   * locations, but because the vertices are logically separate (though at
+   * the same locations) all cells are unconnected and have no neighbors
+   * across faces.
    */
   template <int dim, int spacedim>
   void write_vtu (const Triangulation<dim,spacedim> &tria,