add option for slightly more accurate, and slightly slower algorithm for ray versus convex, used in btCollisionWorld::rayTest.

rayResult.m_flags |= btTriangleRaycastCallback::kF_UseGjkConvexRaytest;
See Demos/RaytestDemo/RaytestDemo.cpp for usage
This fixes issue 146, longest outstanding from 2008.

Demos/RaytestDemo/RaytestDemo.cpp

@@ -68,6 +68,9 @@ void RaytestDemo::castRays()
 			sDebugDraw.drawLine(from,to,btVector4(0,0,0,1));
 			btCollisionWorld::AllHitsRayResultCallback allResults(from,to);
 			allResults.m_flags |= btTriangleRaycastCallback::kF_KeepUnflippedNormal;
+			//optional kF_UseGjkConvexRaytest flag enabled a slightly more accurate and slightly slower algorithm
+			allResults.m_flags |= btTriangleRaycastCallback::kF_UseGjkConvexRaytest;
+			
 			m_dynamicsWorld->rayTest(from,to,allResults);
 
 			for (int i=0;i<allResults.m_hitFractions.size();i++)

src/BulletCollision/CollisionDispatch/btCollisionWorld.cpp

@@ -287,13 +287,19 @@ void	btCollisionWorld::rayTestSingleInternal(const btTransform& rayFromTrans,con
 
 		btConvexShape* convexShape = (btConvexShape*) collisionShape;
 		btVoronoiSimplexSolver	simplexSolver;
-#define USE_SUBSIMPLEX_CONVEX_CAST 1
-#ifdef USE_SUBSIMPLEX_CONVEX_CAST
-		btSubsimplexConvexCast convexCaster(castShape,convexShape,&simplexSolver);
-#else
-		//btGjkConvexCast	convexCaster(castShape,convexShape,&simplexSolver);
+		btSubsimplexConvexCast subSimplexConvexCaster(castShape,convexShape,&simplexSolver);
+		
+		btGjkConvexCast	gjkConvexCaster(castShape,convexShape,&simplexSolver);
+		
 		//btContinuousConvexCollision convexCaster(castShape,convexShape,&simplexSolver,0);
-#endif //#USE_SUBSIMPLEX_CONVEX_CAST
+		bool condition = true;
+		btConvexCast* convexCasterPtr = 0;
+		if (resultCallback.m_flags & btTriangleRaycastCallback::kF_UseGjkConvexRaytest)
+			convexCasterPtr = &gjkConvexCaster;
+		else
+			convexCasterPtr = &subSimplexConvexCaster;
+		
+		btConvexCast& convexCaster = *convexCasterPtr;
 
 		if (convexCaster.calcTimeOfImpact(rayFromTrans,rayToTrans,colObjWorldTransform,colObjWorldTransform,castResult))
 		{

src/BulletCollision/NarrowPhaseCollision/btRaycastCallback.h

@@ -35,7 +35,7 @@ public:
       kF_None                 = 0,
       kF_FilterBackfaces      = 1 << 0,
       kF_KeepUnflippedNormal  = 1 << 1,   // Prevents returned face normal getting flipped when a ray hits a back-facing triangle
-
+	  kF_UseGjkConvexRaytest =  1 << 2,   // Uses a more accurate but slightly slower ray versus convex algorithm
       kF_Terminator        = 0xFFFFFFFF
    };
    unsigned int m_flags;