Add support for generic 2d convex shapes, through wrapper class btConvex2dShape. See Bullet/Demos/Box2dDemo for example wrapping a btCylinderShape and 2d btConvexHullShape.

Add some extra degeneracy debugging check in btGjkPairDetector

src/BulletCollision/CollisionShapes/btBox2dShape.cpp

@@ -0,0 +1,42 @@
+/*
+Bullet Continuous Collision Detection and Physics Library
+Copyright (c) 2003-2006 Erwin Coumans  http://continuousphysics.com/Bullet/
+
+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 "btBox2dShape.h"
+
+
+//{ 
+
+
+void btBox2dShape::getAabb(const btTransform& t,btVector3& aabbMin,btVector3& aabbMax) const
+{
+	btTransformAabb(getHalfExtentsWithoutMargin(),getMargin(),t,aabbMin,aabbMax);
+}
+
+
+void	btBox2dShape::calculateLocalInertia(btScalar mass,btVector3& inertia) const
+{
+	//btScalar margin = btScalar(0.);
+	btVector3 halfExtents = getHalfExtentsWithMargin();
+
+	btScalar lx=btScalar(2.)*(halfExtents.x());
+	btScalar ly=btScalar(2.)*(halfExtents.y());
+	btScalar lz=btScalar(2.)*(halfExtents.z());
+
+	inertia.setValue(mass/(btScalar(12.0)) * (ly*ly + lz*lz),
+					mass/(btScalar(12.0)) * (lx*lx + lz*lz),
+					mass/(btScalar(12.0)) * (lx*lx + ly*ly));
+
+}
+