From 15deee7e79a34add4d0129ffb93ebe7068203d9d Mon Sep 17 00:00:00 2001
From: "erwin.coumans" <erwin.coumans@08e121b0-ae19-0410-a57b-3be3395fd4fd>
Date: Thu, 16 Feb 2012 23:44:43 +0000
Subject: [PATCH] Fix a division by zero in
 btConeTwistConstraint::calcAngleInfo2
 http://bulletphysics.org/Bullet/phpBB3/viewtopic.php?f=9&t=7867 Thanks to
 Aardwolf for report and Roman Ponomarev for the fix

---
 .../ConstraintSolver/btConeTwistConstraint.cpp               | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/BulletDynamics/ConstraintSolver/btConeTwistConstraint.cpp b/src/BulletDynamics/ConstraintSolver/btConeTwistConstraint.cpp
index aa543aabc..755544f0d 100644
--- a/src/BulletDynamics/ConstraintSolver/btConeTwistConstraint.cpp
+++ b/src/BulletDynamics/ConstraintSolver/btConeTwistConstraint.cpp
@@ -638,6 +638,11 @@ void btConeTwistConstraint::calcAngleInfo2(const btTransform& transA, const btTr
 		btTransform trDeltaAB = trB * trPose * trA.inverse();
 		btQuaternion qDeltaAB = trDeltaAB.getRotation();
 		btVector3 swingAxis = 	btVector3(qDeltaAB.x(), qDeltaAB.y(), qDeltaAB.z());
+		float swingAxisLen2 = swingAxis.length2();
+		if(btFuzzyZero(swingAxisLen2))
+		{
+		   return;
+		}
 		m_swingAxis = swingAxis;
 		m_swingAxis.normalize();
 		m_swingCorrection = qDeltaAB.getAngle();