From 84e2856aa11615d2707daa7daedd1680792475f7 Mon Sep 17 00:00:00 2001
From: bangerth <bangerth@0785d39b-7218-0410-832d-ea1e28bc413d>
Date: Tue, 11 May 2010 03:47:29 +0000
Subject: [PATCH] Patch from James Avery: TriaAccessor::extent_in_direction.

git-svn-id: https://svn.dealii.org/trunk@21113 0785d39b-7218-0410-832d-ea1e28bc413d
---
 deal.II/deal.II/include/grid/tria_accessor.h | 20 ++++++++
 deal.II/deal.II/source/grid/tria_accessor.cc | 50 ++++++++++++++++++++
 deal.II/doc/news/changes.h                   |  8 +++-
 3 files changed, 77 insertions(+), 1 deletion(-)

diff --git a/deal.II/deal.II/include/grid/tria_accessor.h b/deal.II/deal.II/include/grid/tria_accessor.h
index 705777b361..a900482b44 100644
--- a/deal.II/deal.II/include/grid/tria_accessor.h
+++ b/deal.II/deal.II/include/grid/tria_accessor.h
@@ -1243,6 +1243,24 @@ class TriaAccessor : public TriaAccessorBase<structdim, dim, spacedim>
 				      */
     double diameter () const;
 
+				     /** 
+				      * Length of an object in the direction
+				      * of the given axis, specified in the
+				      * local coordinate system. See the
+				      * documentation of GeometryInfo for the
+				      * meaning and enumeration of the local
+				      * axes.
+				      *
+				      * Note that the "length" of an object
+				      * can be interpreted in a variety of
+				      * ways. Here, we choose it as the
+				      * maximal length of any of the edges of
+				      * the object that are parallel to the
+				      * chosen axis on the reference cell.
+				      */
+    double extent_in_direction (const unsigned int axis) const;
+
+
     				     /**
 				      * Center of the object. The center of an
 				      * object is defined to be the average of
@@ -1255,6 +1273,8 @@ class TriaAccessor : public TriaAccessorBase<structdim, dim, spacedim>
 				      * object if higher order mappings are
 				      * used.
 				      */
+
+
     Point<spacedim> center () const;
 
 				     /**
diff --git a/deal.II/deal.II/source/grid/tria_accessor.cc b/deal.II/deal.II/source/grid/tria_accessor.cc
index 4f6ab581b5..9458c3ec36 100644
--- a/deal.II/deal.II/source/grid/tria_accessor.cc
+++ b/deal.II/deal.II/source/grid/tria_accessor.cc
@@ -1013,6 +1013,56 @@ measure () const
 }
 
 
+#if deal_II_dimension == 1
+
+template <>
+double TriaAccessor<1,1,1>::extent_in_direction(const unsigned int axis) const
+{
+  Assert (axis == 0, ExcIndexRange (axis, 0, 1));  
+
+  return this->diameter();
+}
+
+#elsif deal_II_dimension == 2
+
+template <>
+double TriaAccessor<2,2,2>::extent_in_direction(const unsigned int axis) const
+{
+  const unsigned int lines[2][2] = {{2,3}, /// Lines along x-axis, see GeometryInfo
+				    {0,1}};/// Lines along y-axis
+
+  Assert (axis < 2, ExcIndexRange (axis, 0, 2));
+  
+  return std::max(this->line(lines[axis][0])->diameter(),
+		  this->line(lines[axis][1])->diameter());
+}
+
+#elsif deal_II_dimension == 3
+
+template <>
+double TriaAccessor<3,3,3>::extent_in_direction(const unsigned int axis) const
+{
+  const unsigned int lines[3][4] = {{2,3,6,7},	   /// Lines along x-axis, see GeometryInfo
+				    {0,1,4,5},    /// Lines along y-axis
+				    {8,9,10,11}}; /// Lines along z-axis
+  
+  Assert (axis < 3, ExcIndexRange (axis, 0, 3));
+
+  double lengths[4] = { this->line(lines[axis][0])->diameter(),
+			this->line(lines[axis][1])->diameter(),
+			this->line(lines[axis][2])->diameter(),
+			this->line(lines[axis][3])->diameter() };
+
+  return std::max(std::max(lengths[0], lengths[1]),
+		  std::max(lengths[2], lengths[3]));
+}
+
+#else
+
+// Not implemented for higher dimensions
+
+#endif
+
 
 /*------------------------ Functions: CellAccessor<1> -----------------------*/
 
diff --git a/deal.II/doc/news/changes.h b/deal.II/doc/news/changes.h
index 607fa3ac4a..c2e85013b5 100644
--- a/deal.II/doc/news/changes.h
+++ b/deal.II/doc/news/changes.h
@@ -629,9 +629,15 @@ inconvenience this causes.
 <h3>deal.II</h3>
 
 <ol>
+  <li>
+  <p>New: TriaAccessor::extent_in_direction() returns the length
+  of an object in a given direction.
+  <br>
+  (James Avery 2010/05/10)
+  </p></li>
+
   <li>
   <p>New: There is a new function DoFTools::extract_dofs_with_support_on_boundary().
-  fixed.
   <br>
   (WB 2010/05/07)
   </p></li>
-- 
2.39.5