support diamondsubdivision (thanks Jay for contribution)

support user-defined broadphase collision filtering (thanks Marten)
make sure btSimpeDynamicsWorld doesn't use cache friendly optimization in the solver (added an assert, and updated BasicDemo)

src/BulletCollision/BroadphaseCollision/btOverlappingPairCache.cpp

@@ -24,7 +24,8 @@ subject to the following restrictions:
 int	gOverlappingPairs = 0;
 
 btOverlappingPairCache::btOverlappingPairCache():
-m_blockedForChanges(false)
+m_blockedForChanges(false),
+m_overlapFilterCallback(0)
 //m_NumOverlapBroadphasePair(0)
 {
 }

src/BulletCollision/BroadphaseCollision/btOverlappingPairCache.h

@@ -26,13 +26,20 @@ subject to the following restrictions:
 
 struct	btOverlapCallback
 {
-virtual ~btOverlapCallback()
-{
-}
+	virtual ~btOverlapCallback()
+	{}
 	//return true for deletion of the pair
 	virtual bool	processOverlap(btBroadphasePair& pair) = 0;
 };
 
+struct btOverlapFilterCallback
+{
+	virtual ~btOverlapFilterCallback()
+	{}
+	// return true when pairs need collision
+	virtual bool	needBroadphaseCollision(btBroadphaseProxy* proxy0,btBroadphaseProxy* proxy1) const = 0;
+};
+
 ///btOverlappingPairCache maintains the objects with overlapping AABB
 ///Typically managed by the Broadphase, Axis3Sweep or btSimpleBroadphase
 class	btOverlappingPairCache : public btBroadphaseInterface
@@ -44,6 +51,8 @@ class	btOverlappingPairCache : public btBroadphaseInterface
 		//during the dispatch, check that user doesn't destroy/create proxy
 		bool		m_blockedForChanges;
 		
+		//if set, use the callback instead of the built in filter in needBroadphaseCollision
+		btOverlapFilterCallback* m_overlapFilterCallback;
 	public:
 			
 		btOverlappingPairCache();	
@@ -67,6 +76,9 @@ class	btOverlappingPairCache : public btBroadphaseInterface
 
 		inline bool needsBroadphaseCollision(btBroadphaseProxy* proxy0,btBroadphaseProxy* proxy1) const
 		{
+			if (m_overlapFilterCallback)
+				return m_overlapFilterCallback->needBroadphaseCollision(proxy0,proxy1);
+
 			bool collides = (proxy0->m_collisionFilterGroup & proxy1->m_collisionFilterMask) != 0;
 			collides = collides && (proxy1->m_collisionFilterGroup & proxy0->m_collisionFilterMask);
 			
@@ -92,7 +104,17 @@ class	btOverlappingPairCache : public btBroadphaseInterface
 			return m_overlappingPairArray.size();
 		}
 		
+		btOverlapFilterCallback* getOverlapFilterCallback()
+		{
+			return m_overlapFilterCallback;
+		}
+
+		void setOverlapFilterCallback(btOverlapFilterCallback* callback)
+		{
+			m_overlapFilterCallback = callback;
+		}
 
 };
 #endif //OVERLAPPING_PAIR_CACHE_H
 
+

src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.cpp

@@ -26,7 +26,8 @@ m_heightfieldDataUnknown(heightfieldData),
 m_maxHeight(maxHeight),
 m_upAxis(upAxis),
 m_useFloatData(useFloatData),
-m_flipQuadEdges(flipQuadEdges)
+m_flipQuadEdges(flipQuadEdges),
+m_useDiamondSubdivision(false)
 {
 
 
@@ -282,38 +283,37 @@ void	btHeightfieldTerrainShape::processAllTriangles(btTriangleCallback* callback
 	}
 
 	
-
+  
 
 	for(int j=startJ; j<endJ; j++)
 	{
 		for(int x=startX; x<endX; x++)
 		{
 			btVector3 vertices[3];
-			if (!m_flipQuadEdges)
+			if (m_flipQuadEdges || (m_useDiamondSubdivision && ((j+x) & 1)))
 			{
-				//first triangle
-				getVertex(x,j,vertices[0]);
-				getVertex(x,j+1,vertices[1]);
-				getVertex(x+1,j,vertices[2]);
-				callback->processTriangle(vertices,x,j);
-				//second triangle
-				getVertex(x+1,j,vertices[0]);
-				getVertex(x,j+1,vertices[1]);
-				getVertex(x+1,j+1,vertices[2]);
-				callback->processTriangle(vertices,x,j);
+        //first triangle
+        getVertex(x,j,vertices[0]);
+        getVertex(x+1,j,vertices[1]);
+        getVertex(x+1,j+1,vertices[2]);
+        callback->processTriangle(vertices,x,j);
+        //second triangle
+        getVertex(x,j,vertices[0]);
+        getVertex(x+1,j+1,vertices[1]);
+        getVertex(x,j+1,vertices[2]);
+        callback->processTriangle(vertices,x,j);				
 			} else
 			{
-				//first triangle
-				getVertex(x,j,vertices[0]);
-				getVertex(x+1,j,vertices[1]);
-				getVertex(x+1,j+1,vertices[2]);
-				callback->processTriangle(vertices,x,j);
-				//second triangle
-				getVertex(x,j,vertices[0]);
-				getVertex(x+1,j+1,vertices[1]);
-				getVertex(x,j+1,vertices[2]);
-				callback->processTriangle(vertices,x,j);
-				
+        //first triangle
+        getVertex(x,j,vertices[0]);
+        getVertex(x,j+1,vertices[1]);
+        getVertex(x+1,j,vertices[2]);
+        callback->processTriangle(vertices,x,j);
+        //second triangle
+        getVertex(x+1,j,vertices[0]);
+        getVertex(x,j+1,vertices[1]);
+        getVertex(x+1,j+1,vertices[2]);
+        callback->processTriangle(vertices,x,j);
 			}
 		}
 	}

src/BulletCollision/CollisionShapes/btHeightfieldTerrainShape.h

@@ -38,6 +38,7 @@ protected:
 	
 	bool	m_useFloatData;
 	bool	m_flipQuadEdges;
+  bool  m_useDiamondSubdivision;
 
 	int	m_upAxis;
 	
@@ -62,6 +63,8 @@ public:
 	virtual ~btHeightfieldTerrainShape();
 
 
+	void setUseDiamondSubdivision(bool useDiamondSubdivision=true) { m_useDiamondSubdivision = useDiamondSubdivision;}
+
 	virtual int	getShapeType() const
 	{
 		return TERRAIN_SHAPE_PROXYTYPE;

src/BulletDynamics/ConstraintSolver/btSequentialImpulseConstraintSolver.cpp

@@ -755,6 +755,10 @@ btScalar btSequentialImpulseConstraintSolver::solveGroup(btCollisionObject** bod
 
 	if (getSolverMode() & SOLVER_CACHE_FRIENDLY)
 	{
+		//you need to provide at least some bodies
+		//btSimpleDynamicsWorld needs to switch off SOLVER_CACHE_FRIENDLY
+		btAssert(bodies);
+		btAssert(numBodies);
 		return solveGroupCacheFriendly(bodies,numBodies,manifoldPtr, numManifolds,constraints,numConstraints,infoGlobal,debugDrawer,stackAlloc);
 	}