Make the btDbvtBroadphase deterministic/reproducable, by sorting the btBroadphasePair using unique ID, instead of proxy address.

The btAxisSweep3 didn't suffer from this issue, because proxies were always allocated in-order, as part of an array.

src/BulletCollision/BroadphaseCollision/btBroadphaseProxy.h

@@ -187,7 +187,7 @@ BT_DECLARE_ALIGNED_ALLOCATOR();
 	{
 
 		//keep them sorted, so the std::set operations work
-		if (&proxy0 < &proxy1)
+		if (proxy0.m_uniqueId < proxy1.m_uniqueId)
         { 
             m_pProxy0 = &proxy0; 
             m_pProxy1 = &proxy1; 
@@ -228,8 +228,8 @@ class btBroadphasePairSortPredicate
 
 		bool operator() ( const btBroadphasePair& a, const btBroadphasePair& b )
 		{
-			 return a.m_pProxy0 > b.m_pProxy0 || 
-				(a.m_pProxy0 == b.m_pProxy0 && a.m_pProxy1 > b.m_pProxy1) ||
+			 return a.m_pProxy0->m_uniqueId > b.m_pProxy0->m_uniqueId || 
+				(a.m_pProxy0 == b.m_pProxy0 && a.m_pProxy1->m_uniqueId > b.m_pProxy1->m_uniqueId) ||
 				(a.m_pProxy0 == b.m_pProxy0 && a.m_pProxy1 == b.m_pProxy1 && a.m_algorithm > b.m_algorithm); 
 		}
 };

src/BulletCollision/BroadphaseCollision/btDbvt.h

@@ -146,9 +146,7 @@ struct	btDbvtAabbMm
 	DBVT_INLINE btScalar			ProjectMinimum(const btVector3& v,unsigned signs) const;
 	DBVT_INLINE friend bool			Intersect(	const btDbvtAabbMm& a,
 		const btDbvtAabbMm& b);
-	DBVT_INLINE friend bool			Intersect(	const btDbvtAabbMm& a,
-		const btDbvtAabbMm& b,
-		const btTransform& xform);
+	
 	DBVT_INLINE friend bool			Intersect(	const btDbvtAabbMm& a,
 		const btVector3& b);
 
@@ -530,21 +528,7 @@ DBVT_INLINE bool		Intersect(	const btDbvtAabbMm& a,
 #endif
 }
 
-//
-DBVT_INLINE bool		Intersect(	const btDbvtAabbMm& a,
-								  const btDbvtAabbMm& b,
-								  const btTransform& xform)
-{
-	const btVector3		d0=xform*b.Center()-a.Center();
-	const btVector3		d1=d0*xform.getBasis();
-	btScalar			s0[2]={0,0};
-	btScalar			s1[2]={dot(xform.getOrigin(),d0),s1[0]};
-	a.AddSpan(d0,s0[0],s0[1]);
-	b.AddSpan(d1,s1[0],s1[1]);
-	if(s0[0]>(s1[1])) return(false);
-	if(s0[1]<(s1[0])) return(false);
-	return(true);
-}
+
 
 //
 DBVT_INLINE bool		Intersect(	const btDbvtAabbMm& a,

src/BulletCollision/BroadphaseCollision/btDbvtBroadphase.cpp

@@ -100,7 +100,8 @@ struct	btDbvtTreeCollider : btDbvt::ICollide
 			btDbvtProxy*	pa=(btDbvtProxy*)na->data;
 			btDbvtProxy*	pb=(btDbvtProxy*)nb->data;
 #if DBVT_BP_SORTPAIRS
-			if(pa>pb) btSwap(pa,pb);
+			if(pa->m_uniqueId>pb->m_uniqueId) 
+				btSwap(pa,pb);
 #endif
 			pbp->m_paircache->addOverlappingPair(pa,pb);
 			++pbp->m_newpairs;
@@ -411,7 +412,8 @@ void							btDbvtBroadphase::collide(btDispatcher* dispatcher)
 				if(!Intersect(pa->leaf->volume,pb->leaf->volume))
 				{
 #if DBVT_BP_SORTPAIRS
-					if(pa>pb) btSwap(pa,pb);
+					if(pa->m_uniqueId>pb->m_uniqueId) 
+						btSwap(pa,pb);
 #endif
 					m_paircache->removeOverlappingPair(pa,pb,dispatcher);
 					--ni;--i;

src/BulletCollision/BroadphaseCollision/btDbvtBroadphase.h

@@ -24,7 +24,7 @@ subject to the following restrictions:
 //
 
 #define	DBVT_BP_PROFILE					0
-#define DBVT_BP_SORTPAIRS				1
+//#define DBVT_BP_SORTPAIRS				1
 #define DBVT_BP_PREVENTFALSEUPDATE		0
 #define DBVT_BP_ACCURATESLEEPING		0
 #define DBVT_BP_ENABLE_BENCHMARK		0

src/BulletCollision/BroadphaseCollision/btOverlappingPairCache.cpp

@@ -135,7 +135,8 @@ void	btHashedOverlappingPairCache::removeOverlappingPairsContainingProxy(btBroad
 btBroadphasePair* btHashedOverlappingPairCache::findPair(btBroadphaseProxy* proxy0, btBroadphaseProxy* proxy1)
 {
 	gFindPairs++;
-	if(proxy0>proxy1) btSwap(proxy0,proxy1);
+	if(proxy0->m_uniqueId>proxy1->m_uniqueId) 
+		btSwap(proxy0,proxy1);
 	int proxyId1 = proxy0->getUid();
 	int proxyId2 = proxy1->getUid();
 
@@ -211,7 +212,8 @@ void	btHashedOverlappingPairCache::growTables()
 
 btBroadphasePair* btHashedOverlappingPairCache::internalAddPair(btBroadphaseProxy* proxy0, btBroadphaseProxy* proxy1)
 {
-	if(proxy0>proxy1) btSwap(proxy0,proxy1);
+	if(proxy0->m_uniqueId>proxy1->m_uniqueId) 
+		btSwap(proxy0,proxy1);
 	int proxyId1 = proxy0->getUid();
 	int proxyId2 = proxy1->getUid();
 
@@ -270,7 +272,8 @@ btBroadphasePair* btHashedOverlappingPairCache::internalAddPair(btBroadphaseProx
 void* btHashedOverlappingPairCache::removeOverlappingPair(btBroadphaseProxy* proxy0, btBroadphaseProxy* proxy1,btDispatcher* dispatcher)
 {
 	gRemovePairs++;
-	if(proxy0>proxy1) btSwap(proxy0,proxy1);
+	if(proxy0->m_uniqueId>proxy1->m_uniqueId) 
+		btSwap(proxy0,proxy1);
 	int proxyId1 = proxy0->getUid();
 	int proxyId2 = proxy1->getUid();