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diff --git a/Source/external/Box2D/Collision/b2CollidePolygon.cpp b/Source/external/Box2D/Collision/b2CollidePolygon.cpp
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+++ b/Source/external/Box2D/Collision/b2CollidePolygon.cpp
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+/*
+* Copyright (c) 2006-2009 Erin Catto http://www.box2d.org
+*
+* This software is provided 'as-is', without any express or implied
+* warranty.  In no event will the authors be held liable for any damages
+* arising from the use of this software.
+* Permission is granted to anyone to use this software for any purpose,
+* including commercial applications, and to alter it and redistribute it
+* freely, subject to the following restrictions:
+* 1. The origin of this software must not be misrepresented; you must not
+* claim that you wrote the original software. If you use this software
+* in a product, an acknowledgment in the product documentation would be
+* appreciated but is not required.
+* 2. Altered source versions must be plainly marked as such, and must not be
+* misrepresented as being the original software.
+* 3. This notice may not be removed or altered from any source distribution.
+*/
+
+#include "Box2D/Collision/b2Collision.h"
+#include "Box2D/Collision/Shapes/b2PolygonShape.h"
+
+// Find the max separation between poly1 and poly2 using edge normals from poly1.
+static float32 b2FindMaxSeparation(int32* edgeIndex,
+								 const b2PolygonShape* poly1, const b2Transform& xf1,
+								 const b2PolygonShape* poly2, const b2Transform& xf2)
+{
+	int32 count1 = poly1->m_count;
+	int32 count2 = poly2->m_count;
+	const b2Vec2* n1s = poly1->m_normals;
+	const b2Vec2* v1s = poly1->m_vertices;
+	const b2Vec2* v2s = poly2->m_vertices;
+	b2Transform xf = b2MulT(xf2, xf1);
+
+	int32 bestIndex = 0;
+	float32 maxSeparation = -b2_maxFloat;
+	for (int32 i = 0; i < count1; ++i)
+	{
+		// Get poly1 normal in frame2.
+		b2Vec2 n = b2Mul(xf.q, n1s[i]);
+		b2Vec2 v1 = b2Mul(xf, v1s[i]);
+
+		// Find deepest point for normal i.
+		float32 si = b2_maxFloat;
+		for (int32 j = 0; j < count2; ++j)
+		{
+			float32 sij = b2Dot(n, v2s[j] - v1);
+			if (sij < si)
+			{
+				si = sij;
+			}
+		}
+
+		if (si > maxSeparation)
+		{
+			maxSeparation = si;
+			bestIndex = i;
+		}
+	}
+
+	*edgeIndex = bestIndex;
+	return maxSeparation;
+}
+
+static void b2FindIncidentEdge(b2ClipVertex c[2],
+							 const b2PolygonShape* poly1, const b2Transform& xf1, int32 edge1,
+							 const b2PolygonShape* poly2, const b2Transform& xf2)
+{
+	const b2Vec2* normals1 = poly1->m_normals;
+
+	int32 count2 = poly2->m_count;
+	const b2Vec2* vertices2 = poly2->m_vertices;
+	const b2Vec2* normals2 = poly2->m_normals;
+
+	b2Assert(0 <= edge1 && edge1 < poly1->m_count);
+
+	// Get the normal of the reference edge in poly2's frame.
+	b2Vec2 normal1 = b2MulT(xf2.q, b2Mul(xf1.q, normals1[edge1]));
+
+	// Find the incident edge on poly2.
+	int32 index = 0;
+	float32 minDot = b2_maxFloat;
+	for (int32 i = 0; i < count2; ++i)
+	{
+		float32 dot = b2Dot(normal1, normals2[i]);
+		if (dot < minDot)
+		{
+			minDot = dot;
+			index = i;
+		}
+	}
+
+	// Build the clip vertices for the incident edge.
+	int32 i1 = index;
+	int32 i2 = i1 + 1 < count2 ? i1 + 1 : 0;
+
+	c[0].v = b2Mul(xf2, vertices2[i1]);
+	c[0].id.cf.indexA = (uint8)edge1;
+	c[0].id.cf.indexB = (uint8)i1;
+	c[0].id.cf.typeA = b2ContactFeature::e_face;
+	c[0].id.cf.typeB = b2ContactFeature::e_vertex;
+
+	c[1].v = b2Mul(xf2, vertices2[i2]);
+	c[1].id.cf.indexA = (uint8)edge1;
+	c[1].id.cf.indexB = (uint8)i2;
+	c[1].id.cf.typeA = b2ContactFeature::e_face;
+	c[1].id.cf.typeB = b2ContactFeature::e_vertex;
+}
+
+// Find edge normal of max separation on A - return if separating axis is found
+// Find edge normal of max separation on B - return if separation axis is found
+// Choose reference edge as min(minA, minB)
+// Find incident edge
+// Clip
+
+// The normal points from 1 to 2
+void b2CollidePolygons(b2Manifold* manifold,
+					  const b2PolygonShape* polyA, const b2Transform& xfA,
+					  const b2PolygonShape* polyB, const b2Transform& xfB)
+{
+	manifold->pointCount = 0;
+	float32 totalRadius = polyA->m_radius + polyB->m_radius;
+
+	int32 edgeA = 0;
+	float32 separationA = b2FindMaxSeparation(&edgeA, polyA, xfA, polyB, xfB);
+	if (separationA > totalRadius)
+		return;
+
+	int32 edgeB = 0;
+	float32 separationB = b2FindMaxSeparation(&edgeB, polyB, xfB, polyA, xfA);
+	if (separationB > totalRadius)
+		return;
+
+	const b2PolygonShape* poly1;	// reference polygon
+	const b2PolygonShape* poly2;	// incident polygon
+	b2Transform xf1, xf2;
+	int32 edge1;					// reference edge
+	uint8 flip;
+	const float32 k_tol = 0.1f * b2_linearSlop;
+
+	if (separationB > separationA + k_tol)
+	{
+		poly1 = polyB;
+		poly2 = polyA;
+		xf1 = xfB;
+		xf2 = xfA;
+		edge1 = edgeB;
+		manifold->type = b2Manifold::e_faceB;
+		flip = 1;
+	}
+	else
+	{
+		poly1 = polyA;
+		poly2 = polyB;
+		xf1 = xfA;
+		xf2 = xfB;
+		edge1 = edgeA;
+		manifold->type = b2Manifold::e_faceA;
+		flip = 0;
+	}
+
+	b2ClipVertex incidentEdge[2];
+	b2FindIncidentEdge(incidentEdge, poly1, xf1, edge1, poly2, xf2);
+
+	int32 count1 = poly1->m_count;
+	const b2Vec2* vertices1 = poly1->m_vertices;
+
+	int32 iv1 = edge1;
+	int32 iv2 = edge1 + 1 < count1 ? edge1 + 1 : 0;
+
+	b2Vec2 v11 = vertices1[iv1];
+	b2Vec2 v12 = vertices1[iv2];
+
+	b2Vec2 localTangent = v12 - v11;
+	localTangent.Normalize();
+	
+	b2Vec2 localNormal = b2Cross(localTangent, 1.0f);
+	b2Vec2 planePoint = 0.5f * (v11 + v12);
+
+	b2Vec2 tangent = b2Mul(xf1.q, localTangent);
+	b2Vec2 normal = b2Cross(tangent, 1.0f);
+	
+	v11 = b2Mul(xf1, v11);
+	v12 = b2Mul(xf1, v12);
+
+	// Face offset.
+	float32 frontOffset = b2Dot(normal, v11);
+
+	// Side offsets, extended by polytope skin thickness.
+	float32 sideOffset1 = -b2Dot(tangent, v11) + totalRadius;
+	float32 sideOffset2 = b2Dot(tangent, v12) + totalRadius;
+
+	// Clip incident edge against extruded edge1 side edges.
+	b2ClipVertex clipPoints1[2];
+	b2ClipVertex clipPoints2[2];
+	int np;
+
+	// Clip to box side 1
+	np = b2ClipSegmentToLine(clipPoints1, incidentEdge, -tangent, sideOffset1, iv1);
+
+	if (np < 2)
+		return;
+
+	// Clip to negative box side 1
+	np = b2ClipSegmentToLine(clipPoints2, clipPoints1,  tangent, sideOffset2, iv2);
+
+	if (np < 2)
+	{
+		return;
+	}
+
+	// Now clipPoints2 contains the clipped points.
+	manifold->localNormal = localNormal;
+	manifold->localPoint = planePoint;
+
+	int32 pointCount = 0;
+	for (int32 i = 0; i < b2_maxManifoldPoints; ++i)
+	{
+		float32 separation = b2Dot(normal, clipPoints2[i].v) - frontOffset;
+
+		if (separation <= totalRadius)
+		{
+			b2ManifoldPoint* cp = manifold->points + pointCount;
+			cp->localPoint = b2MulT(xf2, clipPoints2[i].v);
+			cp->id = clipPoints2[i].id;
+			if (flip)
+			{
+				// Swap features
+				b2ContactFeature cf = cp->id.cf;
+				cp->id.cf.indexA = cf.indexB;
+				cp->id.cf.indexB = cf.indexA;
+				cp->id.cf.typeA = cf.typeB;
+				cp->id.cf.typeB = cf.typeA;
+			}
+			++pointCount;
+		}
+	}
+
+	manifold->pointCount = pointCount;
+}