From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Wed, 27 Feb 2013 04:00:16 +0000 (+0000)
Subject: Add one comment.
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=f37904f12cb8f90cd52c3f1e44673be38a315dd1;p=dealii-svn.git

Add one comment.

git-svn-id: https://svn.dealii.org/trunk@28594 0785d39b-7218-0410-832d-ea1e28bc413d
---

diff --git a/deal.II/examples/step-49/step-49.cc b/deal.II/examples/step-49/step-49.cc
index a79b4031e7..26fb610365 100644
--- a/deal.II/examples/step-49/step-49.cc
+++ b/deal.II/examples/step-49/step-49.cc
@@ -197,6 +197,21 @@ void grid_3 ()
   triangulation.set_boundary (1);
 }
 
+// There is one snag to doing things as shown above: If one moves the nodes on
+// the boundary as shown here, one often ends up with cells in the interior
+// that are badly distorted since the interior nodes were not moved around. This
+// is not that much of a problem in the current case since the mesh did not
+// contain any internal nodes when the nodes were moved -- it was the coarse
+// mesh and it so happened that all vertices are at the boundary. It's also
+// the case that the movement we had here was, compared to the average cell
+// size not overly dramatic. Nevertheless, sometimes one does want to move
+// vertices by a significant distance, and in that case one needs to move
+// internal nodes as well. One way to do that automatically is to call the
+// function GridGenerator::laplace_transformation that takes a set of
+// transformed nodes and moves all of the other nodes in such a way that the
+// resulting mesh has, in some sense, a small distortion.
+
+
 
 // @sect4{grid_4: Demonstrating extrude_triangulation}