From d8ea75afd5b42280d0ddc6e4bfd6d9b772f50b55 Mon Sep 17 00:00:00 2001
From: David Gobbi <david.gobbi@gmail.com>
Date: Tue, 24 Oct 2023 09:47:18 -0600
Subject: [PATCH] Add polygon orientation to ClipClosedSurface doc

---
 Filters/General/vtkClipClosedSurface.h | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/Filters/General/vtkClipClosedSurface.h b/Filters/General/vtkClipClosedSurface.h
index 121e82fbec5..66d638fb092 100644
--- a/Filters/General/vtkClipClosedSurface.h
+++ b/Filters/General/vtkClipClosedSurface.h
@@ -8,6 +8,15 @@
  * collection of clipping planes.  It will produce a new closed surface
  * by creating new polygonal faces where the input data was clipped.
  *
+ * The orientation of the polygons that form the surface is important.
+ * Polygons have a front face and a back face, and it's the back face that
+ * defines the interior or "solid" region of the closed surface.  When a
+ * clipping plane cuts through a "solid" region, a new cut face is generated,
+ * but not when a clipping plane cuts through a hole or "empty" region.  This
+ * distinction is crucial when dealing with complex surfaces.  Note that if
+ * a simple surface has its back faces pointing outwards, then that surface
+ * defines a hole in a potentially infinite solid.
+ *
  * Non-manifold surfaces should not be used as input for this filter.
  * The input surface should have no open edges, and must not have any
  * edges that are shared by more than two faces.  The vtkFeatureEdges
-- 
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