From 2749330633815bbfdd539204f7764c70fee55348 Mon Sep 17 00:00:00 2001
From: David Wells <drwells@email.unc.edu>
Date: Sat, 8 Feb 2020 21:23:22 -0500
Subject: [PATCH] Remove EPS output from step-6.

---
 examples/step-6/doc/results.dox | 15 +++++++++++++++
 examples/step-6/step-6.cc       | 29 ++++++++++++++++-------------
 2 files changed, 31 insertions(+), 13 deletions(-)

diff --git a/examples/step-6/doc/results.dox b/examples/step-6/doc/results.dox
index c622d26075..6de1e95dbd 100644
--- a/examples/step-6/doc/results.dox
+++ b/examples/step-6/doc/results.dox
@@ -247,6 +247,21 @@ the Triangulation what to do when a cell is refined: where should the new
 vertices at the edge midpoints and the cell midpoint be located so that the
 child cells better represent the desired geometry than the parent cell.
 
+To visualize this output, we have to output more lines on <em>interior</em> line
+segments as well as boundary line segments so that the interior lines look
+curved. We can do this by making one change to the gnuplot part of
+<code>output_results</code>:
+@code
+{
+  GridOut       grid_out;
+  std::ofstream output("grid-" + std::to_string(cycle) + ".gnuplot");
+  GridOutFlags::Gnuplot gnuplot_flags(false, 5, /*curved_interior_cells*/true);
+  grid_out.set_flags(gnuplot_flags);
+  MappingQGeneric<dim> mapping(3);
+  grid_out.write_gnuplot(triangulation, output, &mapping);
+}
+@endcode
+
 In the code above, we already do this for faces that sit at the boundary: this
 happens automatically since we use GridGenerator::hyper_ball, which attaches a
 SphericalManifold to the boundary of the domain. To make the mesh
diff --git a/examples/step-6/step-6.cc b/examples/step-6/step-6.cc
index 71e8889a5f..a7cfd5eace 100644
--- a/examples/step-6/step-6.cc
+++ b/examples/step-6/step-6.cc
@@ -464,21 +464,24 @@ void Step6<dim>::refine_grid()
 // cycle.
 //
 // We have already seen in step-1 how this can be achieved for the
-// mesh itself. The only thing we have to change is the generation of
-// the file name, since it should contain the number of the present
-// refinement cycle provided to this function as an argument. To this
-// end, we simply append the number of the refinement cycle as a
-// string to the file name.
-//
-// We also output the solution in the same way as we did before, with
-// a similarly constructed file name.
+// mesh itself. Here, we change a few things:
+// <ol>
+//   <li>We use two different formats: gnuplot and VTU.</li>
+//   <li>We embed the cycle number in the output file name.</li>
+//   <li>For gnuplot output, we set up a GridOutFlags::Gnuplot object to
+//   provide a few extra visualization arguments so that edges appear
+//   curved. This is explained in further detail in step-10.</li>
+// </ol>
 template <int dim>
 void Step6<dim>::output_results(const unsigned int cycle) const
 {
   {
-    GridOut       grid_out;
-    std::ofstream output("grid-" + std::to_string(cycle) + ".eps");
-    grid_out.write_eps(triangulation, output);
+    GridOut               grid_out;
+    std::ofstream         output("grid-" + std::to_string(cycle) + ".gnuplot");
+    GridOutFlags::Gnuplot gnuplot_flags(false, 5);
+    grid_out.set_flags(gnuplot_flags);
+    MappingQGeneric<dim> mapping(3);
+    grid_out.write_gnuplot(triangulation, output, &mapping);
   }
 
   {
@@ -487,8 +490,8 @@ void Step6<dim>::output_results(const unsigned int cycle) const
     data_out.add_data_vector(solution, "solution");
     data_out.build_patches();
 
-    std::ofstream output("solution-" + std::to_string(cycle) + ".vtk");
-    data_out.write_vtk(output);
+    std::ofstream output("solution-" + std::to_string(cycle) + ".vtu");
+    data_out.write_vtu(output);
   }
 }
 
-- 
2.39.5