From c65f94870bbaf7f8e093a9722102bce7099d1b22 Mon Sep 17 00:00:00 2001
From: Jean-Francois Remacle <jean-francois.remacle@uclouvain.be>
Date: Thu, 10 Mar 2011 12:46:47 +0000
Subject: [PATCH]
---
doc/texinfo/gmsh.texi | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)
diff --git a/doc/texinfo/gmsh.texi b/doc/texinfo/gmsh.texi
index d282191ecf..77a37b3546 100644
--- a/doc/texinfo/gmsh.texi
+++ b/doc/texinfo/gmsh.texi
@@ -3906,10 +3906,19 @@ for(i = 0; i < number_of_triangles; i++)@{
@c -------------------------------------------------------------------------
@node Node ordering, Legacy formats, MSH binary file format, File formats
+
@section Node ordering
@cindex Nodes, ordering
+Historically, Gmsh developpers have started by implementing linear elements (lines,
+triangles, quads, tets, prisms and hexes). Then, second and sometimes third
+order elements have been hardcoded. We here distinguish ``low order elements'' that
+have been hardcoded initially and ``high order elements'' that have been coded in
+a general fashion, theoretically valid for any order.
+
+@subsection Low order elements
+
For all mesh and post-processing file formats, the reference elements
are defined as follows.
@@ -4052,9 +4061,12 @@ Pyramid: Pyramid13: Pyramid14:
@end group
@end smallexample
-The nodes of a curved element are numbered in the following order:
+@subsection High order elements
+
+The node ordering of a higher order (possibly curved) element is compatible with the numbering
+of low order element (it is a generalization). We number nodes in the following order:
@itemize --
-@item the element principal vertices;
+@item the element principal or corner vertices;
@item the internal nodes for each edge;
@item the internal nodes for each face;
@item the volume internal nodes.
--
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