From: David Wells <drwells@email.unc.edu>
Date: Thu, 26 Jan 2023 03:32:44 +0000 (-0500)
Subject: Add some comments describing our orientation implementation.
X-Git-Tag: v9.5.0-rc1~593^2
X-Git-Url: https://gitweb.dealii.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F14737%2Fhead;p=dealii.git

Add some comments describing our orientation implementation.
---

diff --git a/include/deal.II/grid/reference_cell.h b/include/deal.II/grid/reference_cell.h
index 286f7f2855..c65f7ae2bd 100644
--- a/include/deal.II/grid/reference_cell.h
+++ b/include/deal.II/grid/reference_cell.h
@@ -1445,7 +1445,10 @@ ReferenceCell::face_reference_cell(const unsigned int face_no) const
 inline constexpr unsigned char
 ReferenceCell::default_combined_face_orientation()
 {
-  return 1u;
+  // Our convention is that 'orientation' has a default value of true and
+  // occupies the least-significant bit while rotate and flip have default
+  // values of 'false' and occupy the second and third bits.
+  return 0b001;
 }
 
 
@@ -1453,7 +1456,9 @@ ReferenceCell::default_combined_face_orientation()
 inline constexpr unsigned char
 ReferenceCell::reversed_combined_line_orientation()
 {
-  return 0u;
+  // For a reversed line 'orientation' is false and neither flip nor rotate are
+  // defined.
+  return 0b000;
 }