+ add option to set pre-tick callback, called at the beginning of each internal simulation step

+ use real-time for soft body demo (using this pre-tick callback)
+ optimize the generation of bending constraints for the special case where the distance is 2

Demos/SoftDemo/SoftDemo.cpp

@@ -98,6 +98,41 @@ void SoftDemo::createStack( btCollisionShape* boxShape, float halfCubeSize, int
 extern int gNumManifold;
 extern int gOverlappingPairs;
 
+///for mouse picking
+void pickingPreTickCallback (btDynamicsWorld *world, btScalar timeStep)
+{
+	SoftDemo* softDemo = (SoftDemo*)world->getWorldUserInfo();
+
+	if(softDemo->m_drag)
+	{
+		const int				x=softDemo->m_lastmousepos[0];
+		const int				y=softDemo->m_lastmousepos[1];
+		const btVector3			rayFrom=softDemo->getCameraPosition();
+		const btVector3			rayTo=softDemo->getRayTo(x,y);
+		const btVector3			rayDir=(rayTo-rayFrom).normalized();
+		const btVector3			N=(softDemo->getCameraTargetPosition()-softDemo->getCameraPosition()).normalized();
+		const btScalar			O=btDot(softDemo->m_impact,N);
+		const btScalar			den=btDot(N,rayDir);
+		if((den*den)>0)
+		{
+			const btScalar			num=O-btDot(N,rayFrom);
+			const btScalar			hit=num/den;
+			if((hit>0)&&(hit<1500))
+			{				
+				softDemo->m_goal=rayFrom+rayDir*hit;
+			}				
+		}		
+		btVector3				delta=softDemo->m_goal-softDemo->m_node->m_x;
+		static const btScalar	maxdrag=10;
+		if(delta.length2()>(maxdrag*maxdrag))
+		{
+			delta=delta.normalized()*maxdrag;
+		}
+		softDemo->m_node->m_v+=delta/timeStep;
+	}
+
+}
+
 
 void SoftDemo::clientMoveAndDisplay()
 {
@@ -106,39 +141,17 @@ void SoftDemo::clientMoveAndDisplay()
 
 
 
-	float dt = 1.0/60.;	
+	float ms = getDeltaTimeMicroseconds();
+	float dt = ms / 1000000.f;//1.0/60.;	
+
+
 
 	if (m_dynamicsWorld)
 	{
-		if(m_drag)
-		{
-			const int				x=m_lastmousepos[0];
-			const int				y=m_lastmousepos[1];
-			const btVector3			rayFrom=m_cameraPosition;
-			const btVector3			rayTo=getRayTo(x,y);
-			const btVector3			rayDir=(rayTo-rayFrom).normalized();
-			const btVector3			N=(m_cameraTargetPosition-m_cameraPosition).normalized();
-			const btScalar			O=btDot(m_impact,N);
-			const btScalar			den=btDot(N,rayDir);
-			if((den*den)>0)
-			{
-				const btScalar			num=O-btDot(N,rayFrom);
-				const btScalar			hit=num/den;
-				if((hit>0)&&(hit<1500))
-				{				
-					m_goal=rayFrom+rayDir*hit;
-				}				
-			}		
-			btVector3				delta=m_goal-m_node->m_x;
-			static const btScalar	maxdrag=10;
-			if(delta.length2()>(maxdrag*maxdrag))
-			{
-				delta=delta.normalized()*maxdrag;
-			}
-			m_node->m_v+=delta/dt;
-		}
 		
-#define FIXED_STEP
+		
+
+//#define FIXED_STEP
 #ifdef FIXED_STEP
 		m_dynamicsWorld->stepSimulation(dt=1.0f/60.f,0);
 
@@ -1246,7 +1259,7 @@ static void	Init_ClusterStackMixed(SoftDemo* pdemo)
 	}
 }
 
-unsigned	current_demo=18;
+unsigned	current_demo=19;
 
 void	SoftDemo::clientResetScene()
 {
@@ -1711,6 +1724,7 @@ void	SoftDemo::initPhysics()
 
 	btDiscreteDynamicsWorld* world = new btSoftRigidDynamicsWorld(m_dispatcher,m_broadphase,m_solver,m_collisionConfiguration);
 	m_dynamicsWorld = world;
+	m_dynamicsWorld->setInternalTickCallback(pickingPreTickCallback,this,true);
 
 
 	m_dynamicsWorld->getDispatchInfo().m_enableSPU = true;

src/BulletDynamics/Dynamics/btContinuousDynamicsWorld.cpp

@@ -48,6 +48,10 @@ void	btContinuousDynamicsWorld::internalSingleStepSimulation( btScalar timeStep)
 	
 	startProfiling(timeStep);
 	
+	if(0 != m_internalPreTickCallback) {
+		(*m_internalPreTickCallback)(this, timeStep);
+	}
+
 
 	///update aabbs information
 	updateAabbs();

src/BulletDynamics/Dynamics/btDiscreteDynamicsWorld.cpp

@@ -362,6 +362,10 @@ void	btDiscreteDynamicsWorld::internalSingleStepSimulation(btScalar timeStep)
 	
 	BT_PROFILE("internalSingleStepSimulation");
 
+	if(0 != m_internalPreTickCallback) {
+		(*m_internalPreTickCallback)(this, timeStep);
+	}	
+
 	///apply gravity, predict motion
 	predictUnconstraintMotion(timeStep);
 

src/BulletDynamics/Dynamics/btDynamicsWorld.h

@@ -41,6 +41,7 @@ class btDynamicsWorld : public btCollisionWorld
 
 protected:
 		btInternalTickCallback m_internalTickCallback;
+		btInternalTickCallback m_internalPreTickCallback;
 		void*	m_worldUserInfo;
 
 		btContactSolverInfo	m_solverInfo;
@@ -49,7 +50,7 @@ public:
 		
 
 		btDynamicsWorld(btDispatcher* dispatcher,btBroadphaseInterface* broadphase,btCollisionConfiguration* collisionConfiguration)
-		:btCollisionWorld(dispatcher,broadphase,collisionConfiguration), m_internalTickCallback(0), m_worldUserInfo(0)
+		:btCollisionWorld(dispatcher,broadphase,collisionConfiguration), m_internalTickCallback(0),m_internalPreTickCallback(0), m_worldUserInfo(0)
 		{
 		}
 
@@ -102,9 +103,15 @@ public:
 		virtual void	clearForces() = 0;
 
 		/// Set the callback for when an internal tick (simulation substep) happens, optional user info
-		void setInternalTickCallback(btInternalTickCallback cb,	void* worldUserInfo=0) 
+		void setInternalTickCallback(btInternalTickCallback cb,	void* worldUserInfo=0,bool isPreTick=false) 
+		{ 
+			if (isPreTick)
+			{
+				m_internalPreTickCallback = cb;
+			} else
 			{
 				m_internalTickCallback = cb; 
+			}
 			m_worldUserInfo = worldUserInfo;
 		}
 

src/BulletSoftBody/btSoftBody.cpp

@@ -704,6 +704,9 @@ void			btSoftBody::clusterDCImpulse(Cluster* cluster,const btVector3& impulse)
 	cluster->m_ndimpulses++;
 }
 
+
+
+
 //
 int				btSoftBody::generateBendingConstraints(int distance,Material* mat)
 {
@@ -715,16 +718,23 @@ int				btSoftBody::generateBendingConstraints(int distance,Material* mat)
 		const int		n=m_nodes.size();
 		const unsigned	inf=(~(unsigned)0)>>1;
 		unsigned*		adj=new unsigned[n*n];
+		
+
 #define IDX(_x_,_y_)	((_y_)*n+(_x_))
 		for(j=0;j<n;++j)
 		{
 			for(i=0;i<n;++i)
 			{
-				if(i!=j)	adj[IDX(i,j)]=adj[IDX(j,i)]=inf;
+				if(i!=j)
+				{
+					adj[IDX(i,j)]=adj[IDX(j,i)]=inf;
+				}
 				else
+				{
 					adj[IDX(i,j)]=adj[IDX(j,i)]=0;
 				}
 			}
+		}
 		for( i=0;i<m_links.size();++i)
 		{
 			const int	ia=(int)(m_links[i].m_n[0]-&m_nodes[0]);
@@ -732,6 +742,59 @@ int				btSoftBody::generateBendingConstraints(int distance,Material* mat)
 			adj[IDX(ia,ib)]=1;
 			adj[IDX(ib,ia)]=1;
 		}
+
+
+		//special optimized case for distance == 2
+		if (distance == 2)
+		{
+
+			struct NodeLinks
+			{
+				btAlignedObjectArray<int> m_links;
+			};
+
+			btAlignedObjectArray<NodeLinks> nodeLinks;
+
+
+			/* Build node links */
+			nodeLinks.resize(m_nodes.size());
+
+			for( i=0;i<m_links.size();++i)
+			{
+				const int	ia=(int)(m_links[i].m_n[0]-&m_nodes[0]);
+				const int	ib=(int)(m_links[i].m_n[1]-&m_nodes[0]);
+				if (nodeLinks[ia].m_links.findLinearSearch(ib)==nodeLinks[ia].m_links.size())
+					nodeLinks[ia].m_links.push_back(ib);
+
+				if (nodeLinks[ib].m_links.findLinearSearch(ia)==nodeLinks[ib].m_links.size())
+					nodeLinks[ib].m_links.push_back(ia);
+			}
+			for (int ii=0;ii<nodeLinks.size();ii++)
+			{
+				int i=ii;
+
+				for (int jj=0;jj<nodeLinks[ii].m_links.size();jj++)
+				{
+					int k = nodeLinks[ii].m_links[jj];
+					for (int kk=0;kk<nodeLinks[k].m_links.size();kk++)
+					{
+						int j = nodeLinks[k].m_links[kk];
+						if (i!=j)
+						{
+							const unsigned	sum=adj[IDX(i,k)]+adj[IDX(k,j)];
+							btAssert(sum==2);
+							if(adj[IDX(i,j)]>sum)
+							{
+								adj[IDX(i,j)]=adj[IDX(j,i)]=sum;
+							}
+						}
+
+					}
+				}
+			}
+		} else
+		{
+			///generic Floyd's algorithm
 			for(int k=0;k<n;++k)
 			{
 				for(j=0;j<n;++j)
@@ -746,6 +809,9 @@ int				btSoftBody::generateBendingConstraints(int distance,Material* mat)
 					}
 				}
 			}
+		}
+
+
 		/* Build links	*/ 
 		int	nlinks=0;
 		for(j=0;j<n;++j)