From 662c04dfdc66188973b46cc2aa295100832c11d9 Mon Sep 17 00:00:00 2001
From: Bill Currie <bill@taniwha.org>
Date: Tue, 15 Nov 2011 20:21:08 +0900
Subject: [PATCH] Add a function to obtain the unit vectors of a winding's
 edges.

---
 include/QF/winding.h  |  9 +++++++++
 libs/models/winding.c | 18 ++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/QF/winding.h b/include/QF/winding.h
index f1a779003..ca116dc20 100644
--- a/include/QF/winding.h
+++ b/include/QF/winding.h
@@ -86,6 +86,15 @@ winding_t *CopyWinding (const winding_t *w);
 */
 winding_t *CopyWindingReverse (const winding_t *w);
 
+/** Create a new "winding" that holds the unit vectors of the edges of the
+	given winding.
+
+	\param w		The winding to convert.
+	\return			The "winding" holding the unit vectors.
+	\note It is the caller's responsibiltiy to free the new winding.
+*/
+winding_t *WindingVectors (const winding_t *w);
+
 /**	Clip the winding to the plain.
 
 	The new winding will be the part of the input winding that is on the
diff --git a/libs/models/winding.c b/libs/models/winding.c
index c5b06cb3a..e75be9731 100644
--- a/libs/models/winding.c
+++ b/libs/models/winding.c
@@ -140,6 +140,24 @@ CopyWindingReverse (const winding_t *w)
 	return c;
 }
 
+winding_t *
+WindingVectors (const winding_t *w)
+{
+	int         i;
+	size_t      size;
+	winding_t  *c;
+
+	size = (size_t) (uintptr_t) &((winding_t *) 0)->points[w->numpoints];
+	c = malloc (size);
+	c->numpoints = w->numpoints;
+	for (i = 0; i < w->numpoints; i++) {
+		VectorSubtract (w->points[(i + 1) % w->numpoints], w->points[i],
+						c->points[i]);
+		VectorNormalize (c->points[i]);
+	}
+	return c;
+}
+
 winding_t *
 ClipWinding (winding_t *in, plane_t *split, qboolean keepon)
 {