Merge pull request #2448 from fuchuyuan/mergechange

merge warmstart

examples/SharedMemory/PhysicsClientC_API.cpp

@@ -752,6 +752,14 @@ B3_SHARED_API int b3PhysicsParamSetWarmStartingFactor(b3SharedMemoryCommandHandl
 	return 0;
 }
 
+B3_SHARED_API int b3PhysicsParamSetArticulatedWarmStartingFactor(b3SharedMemoryCommandHandle commandHandle, double warmStartingFactor)
+{
+	struct SharedMemoryCommand* command = (struct SharedMemoryCommand*)commandHandle;
+	b3Assert(command->m_type == CMD_SEND_PHYSICS_SIMULATION_PARAMETERS);
+	command->m_physSimParamArgs.m_articulatedWarmStartingFactor = warmStartingFactor;
+	command->m_updateFlags |= SIM_PARAM_UPDATE_ARTICULATED_WARM_STARTING_FACTOR;
+	return 0;
+}
 B3_SHARED_API int b3PhysicsParamSetSolverResidualThreshold(b3SharedMemoryCommandHandle commandHandle, double solverResidualThreshold)
 {
 	struct SharedMemoryCommand* command = (struct SharedMemoryCommand*)commandHandle;

examples/SharedMemory/PhysicsClientC_API.h

@@ -339,6 +339,7 @@ extern "C"
 	B3_SHARED_API int b3PhysicsParamSetRealTimeSimulation(b3SharedMemoryCommandHandle commandHandle, int enableRealTimeSimulation);
 	B3_SHARED_API int b3PhysicsParamSetNumSolverIterations(b3SharedMemoryCommandHandle commandHandle, int numSolverIterations);
 	B3_SHARED_API int b3PhysicsParamSetWarmStartingFactor(b3SharedMemoryCommandHandle commandHandle, double warmStartingFactor);
+	B3_SHARED_API int b3PhysicsParamSetArticulatedWarmStartingFactor(b3SharedMemoryCommandHandle commandHandle, double warmStartingFactor);
 	B3_SHARED_API int b3PhysicsParamSetCollisionFilterMode(b3SharedMemoryCommandHandle commandHandle, int filterMode);
 	B3_SHARED_API int b3PhysicsParamSetUseSplitImpulse(b3SharedMemoryCommandHandle commandHandle, int useSplitImpulse);
 	B3_SHARED_API int b3PhysicsParamSetSplitImpulsePenetrationThreshold(b3SharedMemoryCommandHandle commandHandle, double splitImpulsePenetrationThreshold);

examples/SharedMemory/PhysicsServerCommandProcessor.cpp

@@ -9338,6 +9338,12 @@ bool PhysicsServerCommandProcessor::processSendPhysicsParametersCommand(const st
 	{
 		m_data->m_dynamicsWorld->getSolverInfo().m_warmstartingFactor = clientCmd.m_physSimParamArgs.m_warmStartingFactor;
 	}
+
+	if (clientCmd.m_updateFlags & SIM_PARAM_UPDATE_ARTICULATED_WARM_STARTING_FACTOR)
+	{
+		m_data->m_dynamicsWorld->getSolverInfo().m_solverMode |= SOLVER_USE_ARTICULATED_WARMSTARTING;
+		m_data->m_dynamicsWorld->getSolverInfo().m_articulatedWarmstartingFactor = clientCmd.m_physSimParamArgs.m_articulatedWarmStartingFactor;
+	}
 	SharedMemoryStatus& serverCmd = serverStatusOut;
 	serverCmd.m_type = CMD_CLIENT_COMMAND_COMPLETED;
 	return hasStatus;

examples/SharedMemory/SharedMemoryCommands.h

@@ -483,6 +483,7 @@ enum EnumSimParamUpdateFlags
 	SIM_PARAM_CONSTRAINT_MIN_SOLVER_ISLAND_SIZE = 1 << 25,
 	SIM_PARAM_REPORT_CONSTRAINT_SOLVER_ANALYTICS = 1 << 26,
 	SIM_PARAM_UPDATE_WARM_STARTING_FACTOR = 1 << 27,
+	SIM_PARAM_UPDATE_ARTICULATED_WARM_STARTING_FACTOR = 1 << 28,
         
 };
 

examples/SharedMemory/SharedMemoryPublic.h

@@ -947,6 +947,7 @@ struct b3PhysicsSimulationParameters
 	int m_numSimulationSubSteps;
 	int m_numSolverIterations;
 	double m_warmStartingFactor;
+	double m_articulatedWarmStartingFactor;
 	int m_useRealTimeSimulation;
 	int m_useSplitImpulse;
 	double m_splitImpulsePenetrationThreshold;

src/BulletCollision/NarrowPhaseCollision/btManifoldPoint.h

@@ -55,6 +55,7 @@ public:
 		: m_userPersistentData(0),
 		  m_contactPointFlags(0),
 		  m_appliedImpulse(0.f),
+		  m_prevRHS(0.f),
 		  m_appliedImpulseLateral1(0.f),
 		  m_appliedImpulseLateral2(0.f),
 		  m_contactMotion1(0.f),
@@ -79,6 +80,7 @@ public:
 										 m_userPersistentData(0),
 										 m_contactPointFlags(0),
 										 m_appliedImpulse(0.f),
+										 m_prevRHS(0.f),
 										 m_appliedImpulseLateral1(0.f),
 										 m_appliedImpulseLateral2(0.f),
 										 m_contactMotion1(0.f),
@@ -114,6 +116,7 @@ public:
 	int m_contactPointFlags;
 
 	btScalar m_appliedImpulse;
+	btScalar m_prevRHS;
 	btScalar m_appliedImpulseLateral1;
 	btScalar m_appliedImpulseLateral2;
 	btScalar m_contactMotion1;

src/BulletCollision/NarrowPhaseCollision/btPersistentManifold.cpp

@@ -325,6 +325,7 @@ const char* btPersistentManifold::serialize(const class btPersistentManifold* ma
 	{
 		const btManifoldPoint& pt = manifold->getContactPoint(i);
 		dataOut->m_pointCacheAppliedImpulse[i] = pt.m_appliedImpulse;
+		dataOut->m_pointCachePrevRHS[i] = pt.m_prevRHS;
 		dataOut->m_pointCacheAppliedImpulseLateral1[i] = pt.m_appliedImpulseLateral1;
 		dataOut->m_pointCacheAppliedImpulseLateral2[i] = pt.m_appliedImpulseLateral2;
 		pt.m_localPointA.serialize(dataOut->m_pointCacheLocalPointA[i]);
@@ -371,6 +372,7 @@ void btPersistentManifold::deSerialize(const struct btPersistentManifoldDoubleDa
 		btManifoldPoint& pt = m_pointCache[i];
 
 		pt.m_appliedImpulse = manifoldDataPtr->m_pointCacheAppliedImpulse[i];
+		pt.m_prevRHS = manifoldDataPtr->m_pointCachePrevRHS[i];
 		pt.m_appliedImpulseLateral1 = manifoldDataPtr->m_pointCacheAppliedImpulseLateral1[i];
 		pt.m_appliedImpulseLateral2 = manifoldDataPtr->m_pointCacheAppliedImpulseLateral2[i];
 		pt.m_localPointA.deSerializeDouble(manifoldDataPtr->m_pointCacheLocalPointA[i]);
@@ -416,6 +418,7 @@ void btPersistentManifold::deSerialize(const struct btPersistentManifoldFloatDat
 		btManifoldPoint& pt = m_pointCache[i];
 
 		pt.m_appliedImpulse = manifoldDataPtr->m_pointCacheAppliedImpulse[i];
+		pt.m_prevRHS = manifoldDataPtr->m_pointCachePrevRHS[i];
 		pt.m_appliedImpulseLateral1 = manifoldDataPtr->m_pointCacheAppliedImpulseLateral1[i];
 		pt.m_appliedImpulseLateral2 = manifoldDataPtr->m_pointCacheAppliedImpulseLateral2[i];
 		pt.m_localPointA.deSerialize(manifoldDataPtr->m_pointCacheLocalPointA[i]);

src/BulletCollision/NarrowPhaseCollision/btPersistentManifold.h

@@ -173,6 +173,7 @@ public:
 			//get rid of duplicated userPersistentData pointer
 			m_pointCache[lastUsedIndex].m_userPersistentData = 0;
 			m_pointCache[lastUsedIndex].m_appliedImpulse = 0.f;
+			m_pointCache[lastUsedIndex].m_prevRHS = 0.f;
 			m_pointCache[lastUsedIndex].m_contactPointFlags = 0;
 			m_pointCache[lastUsedIndex].m_appliedImpulseLateral1 = 0.f;
 			m_pointCache[lastUsedIndex].m_appliedImpulseLateral2 = 0.f;
@@ -195,6 +196,7 @@ public:
 #ifdef MAINTAIN_PERSISTENCY
 		int lifeTime = m_pointCache[insertIndex].getLifeTime();
 		btScalar appliedImpulse = m_pointCache[insertIndex].m_appliedImpulse;
+		btScalar prevRHS = m_pointCache[insertIndex].m_prevRHS;
 		btScalar appliedLateralImpulse1 = m_pointCache[insertIndex].m_appliedImpulseLateral1;
 		btScalar appliedLateralImpulse2 = m_pointCache[insertIndex].m_appliedImpulseLateral2;
 
@@ -223,6 +225,7 @@ public:
 			m_pointCache[insertIndex] = newPoint;
 			m_pointCache[insertIndex].m_userPersistentData = cache;
 			m_pointCache[insertIndex].m_appliedImpulse = appliedImpulse;
+			m_pointCache[insertIndex].m_prevRHS = prevRHS;
 			m_pointCache[insertIndex].m_appliedImpulseLateral1 = appliedLateralImpulse1;
 			m_pointCache[insertIndex].m_appliedImpulseLateral2 = appliedLateralImpulse2;
 		}
@@ -276,6 +279,7 @@ struct btPersistentManifoldDoubleData
 	btVector3DoubleData	m_pointCacheLateralFrictionDir2[4];
 	double m_pointCacheDistance[4];
 	double m_pointCacheAppliedImpulse[4];
+	double m_pointCachePrevRHS[4];
 	 double m_pointCacheCombinedFriction[4];
 	double m_pointCacheCombinedRollingFriction[4];
 	double m_pointCacheCombinedSpinningFriction[4];
@@ -322,6 +326,7 @@ struct btPersistentManifoldFloatData
 	btVector3FloatData	m_pointCacheLateralFrictionDir2[4];
 	float m_pointCacheDistance[4];
 	float m_pointCacheAppliedImpulse[4];
+	float m_pointCachePrevRHS[4];
 	float m_pointCacheCombinedFriction[4];
 	float m_pointCacheCombinedRollingFriction[4];
 	float m_pointCacheCombinedSpinningFriction[4];

src/BulletDynamics/ConstraintSolver/btContactSolverInfo.h

@@ -30,7 +30,8 @@ enum btSolverMode
 	SOLVER_SIMD = 256,
 	SOLVER_INTERLEAVE_CONTACT_AND_FRICTION_CONSTRAINTS = 512,
 	SOLVER_ALLOW_ZERO_LENGTH_FRICTION_DIRECTIONS = 1024,
-	SOLVER_DISABLE_IMPLICIT_CONE_FRICTION = 2048
+	SOLVER_DISABLE_IMPLICIT_CONE_FRICTION = 2048,
+	SOLVER_USE_ARTICULATED_WARMSTARTING = 4096,
 };
 
 struct btContactSolverInfoData
@@ -54,7 +55,7 @@ struct btContactSolverInfoData
 	btScalar m_splitImpulseTurnErp;
 	btScalar m_linearSlop;
 	btScalar m_warmstartingFactor;
-
+	btScalar m_articulatedWarmstartingFactor;
 	int m_solverMode;
 	int m_restingContactRestitutionThreshold;
 	int m_minimumSolverBatchSize;
@@ -89,6 +90,7 @@ struct btContactSolverInfo : public btContactSolverInfoData
 		m_splitImpulseTurnErp = 0.1f;
 		m_linearSlop = btScalar(0.0);
 		m_warmstartingFactor = btScalar(0.85);
+		m_articulatedWarmstartingFactor = btScalar(0.85);
 		//m_solverMode =  SOLVER_USE_WARMSTARTING |  SOLVER_SIMD | SOLVER_DISABLE_VELOCITY_DEPENDENT_FRICTION_DIRECTION|SOLVER_USE_2_FRICTION_DIRECTIONS|SOLVER_ENABLE_FRICTION_DIRECTION_CACHING;// | SOLVER_RANDMIZE_ORDER;
 		m_solverMode = SOLVER_USE_WARMSTARTING | SOLVER_SIMD;  // | SOLVER_RANDMIZE_ORDER;
 		m_restingContactRestitutionThreshold = 2;              //unused as of 2.81
@@ -120,6 +122,7 @@ struct btContactSolverInfoDoubleData
 	double m_splitImpulseTurnErp;
 	double m_linearSlop;
 	double m_warmstartingFactor;
+	double m_articulatedWarmstartingFactor;
 	double m_maxGyroscopicForce;  ///it is only used for 'explicit' version of gyroscopic force
 	double m_singleAxisRollingFrictionThreshold;
 
@@ -150,6 +153,7 @@ struct btContactSolverInfoFloatData
 
 	float m_linearSlop;
 	float m_warmstartingFactor;
+	float m_articulatedWarmstartingFactor;
 	float m_maxGyroscopicForce;
 	float m_singleAxisRollingFrictionThreshold;
 

src/BulletDynamics/Featherstone/btMultiBodyConstraint.cpp

@@ -342,40 +342,6 @@ btScalar btMultiBodyConstraint::fillMultiBodyConstraint(btMultiBodySolverConstra
 		solverConstraint.m_friction = 0.f;  //cp.m_combinedFriction;
 	}
 
-	///warm starting (or zero if disabled)
-	/*
-     if (infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
-     {
-     solverConstraint.m_appliedImpulse = isFriction ? 0 : cp.m_appliedImpulse * infoGlobal.m_warmstartingFactor;
-     
-     if (solverConstraint.m_appliedImpulse)
-     {
-     if (multiBodyA)
-     {
-     btScalar impulse = solverConstraint.m_appliedImpulse;
-     btScalar* deltaV = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
-     multiBodyA->applyDeltaVee(deltaV,impulse);
-     applyDeltaVee(data,deltaV,impulse,solverConstraint.m_deltaVelAindex,ndofA);
-     } else
-     {
-     if (rb0)
-					bodyA->internalApplyImpulse(solverConstraint.m_contactNormal1*bodyA->internalGetInvMass()*rb0->getLinearFactor(),solverConstraint.m_angularComponentA,solverConstraint.m_appliedImpulse);
-     }
-     if (multiBodyB)
-     {
-     btScalar impulse = solverConstraint.m_appliedImpulse;
-     btScalar* deltaV = &data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
-     multiBodyB->applyDeltaVee(deltaV,impulse);
-     applyDeltaVee(data,deltaV,impulse,solverConstraint.m_deltaVelBindex,ndofB);
-     } else
-     {
-     if (rb1)
-					bodyB->internalApplyImpulse(-solverConstraint.m_contactNormal2*bodyB->internalGetInvMass()*rb1->getLinearFactor(),-solverConstraint.m_angularComponentB,-(btScalar)solverConstraint.m_appliedImpulse);
-     }
-     }
-     } else
-     */
-
 	solverConstraint.m_appliedImpulse = 0.f;
 	solverConstraint.m_appliedPushImpulse = 0.f;
 

src/BulletDynamics/Featherstone/btMultiBodyConstraintSolver.cpp

@@ -22,6 +22,8 @@ subject to the following restrictions:
 #include "BulletDynamics/ConstraintSolver/btContactSolverInfo.h"
 
 #include "LinearMath/btQuickprof.h"
+#include "BulletDynamics/Featherstone/btMultiBodySolverConstraint.h"
+#include "LinearMath/btScalar.h"
 
 btScalar btMultiBodyConstraintSolver::solveSingleIteration(int iteration, btCollisionObject** bodies, int numBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer)
 {
@@ -491,11 +493,7 @@ btScalar btMultiBodyConstraintSolver::resolveConeFrictionConstraintRows(const bt
 	return deltaVel;
 }
 
-void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySolverConstraint& solverConstraint,
+void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySolverConstraint& solverConstraint, const btVector3& contactNormal, const btScalar& appliedImpulse, btManifoldPoint& cp, const btContactSolverInfo& infoGlobal, btScalar& relaxation, bool isFriction, btScalar desiredVelocity, btScalar cfmSlip)
-																  const btVector3& contactNormal,
-																  btManifoldPoint& cp, const btContactSolverInfo& infoGlobal,
-																  btScalar& relaxation,
-																  bool isFriction, btScalar desiredVelocity, btScalar cfmSlip)
 {
 	BT_PROFILE("setupMultiBodyContactConstraint");
 	btVector3 rel_pos1;
@@ -781,48 +779,6 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
 		}
 	}
 
-	///warm starting (or zero if disabled)
-	//disable warmstarting for btMultiBody, it has issues gaining energy (==explosion)
-	if (/* DISABLES CODE */ (0)) //infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
-	{
-		solverConstraint.m_appliedImpulse = isFriction ? 0 : cp.m_appliedImpulse * infoGlobal.m_warmstartingFactor;
-
-		if (solverConstraint.m_appliedImpulse)
-		{
-			if (multiBodyA)
-			{
-				btScalar impulse = solverConstraint.m_appliedImpulse;
-				btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
-				multiBodyA->applyDeltaVeeMultiDof(deltaV, impulse);
-
-				applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelAindex, ndofA);
-			}
-			else
-			{
-				if (rb0)
-					bodyA->internalApplyImpulse(solverConstraint.m_contactNormal1 * bodyA->internalGetInvMass() * rb0->getLinearFactor(), solverConstraint.m_angularComponentA, solverConstraint.m_appliedImpulse);
-			}
-			if (multiBodyB)
-			{
-				btScalar impulse = solverConstraint.m_appliedImpulse;
-				btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
-				multiBodyB->applyDeltaVeeMultiDof(deltaV, impulse);
-				applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelBindex, ndofB);
-			}
-			else
-			{
-				if (rb1)
-					bodyB->internalApplyImpulse(-solverConstraint.m_contactNormal2 * bodyB->internalGetInvMass() * rb1->getLinearFactor(), -solverConstraint.m_angularComponentB, -(btScalar)solverConstraint.m_appliedImpulse);
-			}
-		}
-	}
-	else
-	{
-		solverConstraint.m_appliedImpulse = 0.f;
-	}
-
-	solverConstraint.m_appliedPushImpulse = 0.f;
-
 	{
 		btScalar positionalError = 0.f;
 		btScalar velocityError = restitution - rel_vel;  // * damping;	//note for friction restitution is always set to 0 (check above) so it is acutally velocityError = -rel_vel for friction
@@ -874,6 +830,54 @@ void btMultiBodyConstraintSolver::setupMultiBodyContactConstraint(btMultiBodySol
 
 		solverConstraint.m_cfm = cfm * solverConstraint.m_jacDiagABInv;
 	}
+        
+	if (infoGlobal.m_solverMode & SOLVER_USE_ARTICULATED_WARMSTARTING)
+	{
+		if (btFabs(cp.m_prevRHS) > 1e-5 && cp.m_prevRHS < 2* solverConstraint.m_rhs && solverConstraint.m_rhs < 2*cp.m_prevRHS)
+		{
+			solverConstraint.m_appliedImpulse = isFriction ? 0 : cp.m_appliedImpulse / cp.m_prevRHS * solverConstraint.m_rhs * infoGlobal.m_articulatedWarmstartingFactor;
+			if (solverConstraint.m_appliedImpulse < 0)
+				solverConstraint.m_appliedImpulse = 0;
+		}
+		else
+		{
+			solverConstraint.m_appliedImpulse = 0.f;
+		}
+
+		if (solverConstraint.m_appliedImpulse)
+		{
+			if (multiBodyA)
+			{
+				btScalar impulse = solverConstraint.m_appliedImpulse;
+				btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
+				multiBodyA->applyDeltaVeeMultiDof2(deltaV, impulse);
+
+				applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelAindex, ndofA);
+			}
+			else
+			{
+				if (rb0)
+					bodyA->internalApplyImpulse(solverConstraint.m_contactNormal1 * bodyA->internalGetInvMass() * rb0->getLinearFactor(), solverConstraint.m_angularComponentA, solverConstraint.m_appliedImpulse);
+			}
+			if (multiBodyB)
+			{
+				btScalar impulse = solverConstraint.m_appliedImpulse;
+				btScalar* deltaV = &m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
+				multiBodyB->applyDeltaVeeMultiDof2(deltaV, impulse);
+				applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelBindex, ndofB);
+			}
+			else
+			{
+				if (rb1)
+					bodyB->internalApplyImpulse(-solverConstraint.m_contactNormal2 * bodyB->internalGetInvMass() * rb1->getLinearFactor(), -solverConstraint.m_angularComponentB, -(btScalar)solverConstraint.m_appliedImpulse);
+			}
+		}
+	}
+	else
+	{
+		solverConstraint.m_appliedImpulse = 0.f;
+   	solverConstraint.m_appliedPushImpulse = 0.f;
+	}
 }
 
 void btMultiBodyConstraintSolver::setupMultiBodyTorsionalFrictionConstraint(btMultiBodySolverConstraint& solverConstraint,
@@ -1130,7 +1134,7 @@ void btMultiBodyConstraintSolver::setupMultiBodyTorsionalFrictionConstraint(btMu
 	}
 }
 
-btMultiBodySolverConstraint& btMultiBodyConstraintSolver::addMultiBodyFrictionConstraint(const btVector3& normalAxis, btPersistentManifold* manifold, int frictionIndex, btManifoldPoint& cp, btCollisionObject* colObj0, btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
+btMultiBodySolverConstraint& btMultiBodyConstraintSolver::addMultiBodyFrictionConstraint(const btVector3& normalAxis, const btScalar& appliedImpulse, btPersistentManifold* manifold, int frictionIndex, btManifoldPoint& cp, btCollisionObject* colObj0, btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity, btScalar cfmSlip)
 {
 	BT_PROFILE("addMultiBodyFrictionConstraint");
 	btMultiBodySolverConstraint& solverConstraint = m_multiBodyFrictionContactConstraints.expandNonInitializing();
@@ -1161,7 +1165,7 @@ btMultiBodySolverConstraint& btMultiBodyConstraintSolver::addMultiBodyFrictionCo
 
 	solverConstraint.m_originalContactPoint = &cp;
 
-	setupMultiBodyContactConstraint(solverConstraint, normalAxis, cp, infoGlobal, relaxation, isFriction, desiredVelocity, cfmSlip);
+	setupMultiBodyContactConstraint(solverConstraint, normalAxis, 0, cp, infoGlobal, relaxation, isFriction, desiredVelocity, cfmSlip);
 	return solverConstraint;
 }
 
@@ -1297,7 +1301,7 @@ void btMultiBodyConstraintSolver::convertMultiBodyContact(btPersistentManifold*
 			solverConstraint.m_originalContactPoint = &cp;
 
 			bool isFriction = false;
-			setupMultiBodyContactConstraint(solverConstraint, cp.m_normalWorldOnB, cp, infoGlobal, relaxation, isFriction);
+			setupMultiBodyContactConstraint(solverConstraint, cp.m_normalWorldOnB, cp.m_appliedImpulse, cp, infoGlobal, relaxation, isFriction);
 
 			//			const btVector3& pos1 = cp.getPositionWorldOnA();
 			//			const btVector3& pos2 = cp.getPositionWorldOnB();
@@ -1371,13 +1375,13 @@ void btMultiBodyConstraintSolver::convertMultiBodyContact(btPersistentManifold*
 				{
 					applyAnisotropicFriction(colObj0, cp.m_lateralFrictionDir1, btCollisionObject::CF_ANISOTROPIC_FRICTION);
 					applyAnisotropicFriction(colObj1, cp.m_lateralFrictionDir1, btCollisionObject::CF_ANISOTROPIC_FRICTION);
-					addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal);
+					addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1, cp.m_appliedImpulseLateral1, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal);
 
 					if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
 					{
 						applyAnisotropicFriction(colObj0, cp.m_lateralFrictionDir2, btCollisionObject::CF_ANISOTROPIC_FRICTION);
 						applyAnisotropicFriction(colObj1, cp.m_lateralFrictionDir2, btCollisionObject::CF_ANISOTROPIC_FRICTION);
-						addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal);
+					  addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2, cp.m_appliedImpulseLateral2, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal);
 					}
 
 					if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS) && (infoGlobal.m_solverMode & SOLVER_DISABLE_VELOCITY_DEPENDENT_FRICTION_DIRECTION))
@@ -1388,26 +1392,27 @@ void btMultiBodyConstraintSolver::convertMultiBodyContact(btPersistentManifold*
 			}
 			else
 			{
-				addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal, cp.m_contactMotion1, cp.m_frictionCFM);
+				addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir1, cp.m_appliedImpulseLateral1, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal, cp.m_contactMotion1, cp.m_frictionCFM);
 
 				if ((infoGlobal.m_solverMode & SOLVER_USE_2_FRICTION_DIRECTIONS))
-					addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal, cp.m_contactMotion2, cp.m_frictionCFM);
+					addMultiBodyFrictionConstraint(cp.m_lateralFrictionDir2, cp.m_appliedImpulseLateral2, manifold, frictionIndex, cp, colObj0, colObj1, relaxation, infoGlobal, cp.m_contactMotion2, cp.m_frictionCFM);
-
-				//setMultiBodyFrictionConstraintImpulse( solverConstraint, solverBodyIdA, solverBodyIdB, cp, infoGlobal);
-				//todo:
 				solverConstraint.m_appliedImpulse = 0.f;
 				solverConstraint.m_appliedPushImpulse = 0.f;
       }
 
 #endif  //ENABLE_FRICTION
 		}
+		else
+		{
+			// Reset quantities related to warmstart as 0.
+			cp.m_appliedImpulse = 0;
+			cp.m_prevRHS = 0;
+		}
 	}
 }
 
 void btMultiBodyConstraintSolver::convertContacts(btPersistentManifold** manifoldPtr, int numManifolds, const btContactSolverInfo& infoGlobal)
 {
-	//btPersistentManifold* manifold = 0;
-
 	for (int i = 0; i < numManifolds; i++)
 	{
 		btPersistentManifold* manifold = manifoldPtr[i];
@@ -1434,6 +1439,51 @@ void btMultiBodyConstraintSolver::convertContacts(btPersistentManifold** manifol
 
 		c->createConstraintRows(m_multiBodyNonContactConstraints, m_data, infoGlobal);
 	}
+
+	// Warmstart for noncontact constraints
+	if (infoGlobal.m_solverMode & SOLVER_USE_ARTICULATED_WARMSTARTING)
+	{
+		for (int i = 0; i < m_multiBodyNonContactConstraints.size(); i++)
+		{
+			btMultiBodySolverConstraint& solverConstraint =
+				m_multiBodyNonContactConstraints[i];
+			solverConstraint.m_appliedImpulse =
+				solverConstraint.m_orgConstraint->getAppliedImpulse(solverConstraint.m_orgDofIndex) *
+				infoGlobal.m_articulatedWarmstartingFactor;
+
+			btMultiBody* multiBodyA = solverConstraint.m_multiBodyA;
+			btMultiBody* multiBodyB = solverConstraint.m_multiBodyB;
+			if (solverConstraint.m_appliedImpulse)
+			{
+				if (multiBodyA)
+				{
+					int ndofA = multiBodyA->getNumDofs() + 6;
+					btScalar* deltaV =
+						&m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacAindex];
+					btScalar impulse = solverConstraint.m_appliedImpulse;
+					multiBodyA->applyDeltaVeeMultiDof2(deltaV, impulse);
+					applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelAindex, ndofA);
+				}
+				if (multiBodyB)
+				{
+					int ndofB = multiBodyB->getNumDofs() + 6;
+					btScalar* deltaV =
+						&m_data.m_deltaVelocitiesUnitImpulse[solverConstraint.m_jacBindex];
+					btScalar impulse = solverConstraint.m_appliedImpulse;
+					multiBodyB->applyDeltaVeeMultiDof2(deltaV, impulse);
+					applyDeltaVee(deltaV, impulse, solverConstraint.m_deltaVelBindex, ndofB);
+				}
+			}
+		}
+	}
+	else
+	{
+		for (int i = 0; i < m_multiBodyNonContactConstraints.size(); i++)
+		{
+			btMultiBodySolverConstraint& solverConstraint = m_multiBodyNonContactConstraints[i];
+			solverConstraint.m_appliedImpulse = 0;
+		}
+	}
 }
 
 btScalar btMultiBodyConstraintSolver::solveGroup(btCollisionObject** bodies, int numBodies, btPersistentManifold** manifold, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& info, btIDebugDraw* debugDrawer, btDispatcher* dispatcher)
@@ -1556,7 +1606,7 @@ btScalar btMultiBodyConstraintSolver::solveGroupCacheFriendlyFinish(btCollisionO
 		writeBackSolverBodyToMultiBody(solverConstraint, infoGlobal.m_timeStep);
 	}
 
-	if (infoGlobal.m_solverMode & SOLVER_USE_WARMSTARTING)
+
 	{
 		BT_PROFILE("warm starting write back");
 		for (int j = 0; j < numPoolConstraints; j++)
@@ -1565,6 +1615,7 @@ btScalar btMultiBodyConstraintSolver::solveGroupCacheFriendlyFinish(btCollisionO
 			btManifoldPoint* pt = (btManifoldPoint*)solverConstraint.m_originalContactPoint;
 			btAssert(pt);
 			pt->m_appliedImpulse = solverConstraint.m_appliedImpulse;
+ 		  pt->m_prevRHS = solverConstraint.m_rhs;
 			pt->m_appliedImpulseLateral1 = m_multiBodyFrictionContactConstraints[solverConstraint.m_frictionIndex].m_appliedImpulse;
 
 			//printf("pt->m_appliedImpulseLateral1 = %f\n", pt->m_appliedImpulseLateral1);
@@ -1576,9 +1627,8 @@ btScalar btMultiBodyConstraintSolver::solveGroupCacheFriendlyFinish(btCollisionO
 				pt->m_appliedImpulseLateral2 = 0;
 			}
 		}
-		
-			//do a callback here?
 	}
+
 #if 0
 	//multibody joint feedback
 	{

src/BulletDynamics/Featherstone/btMultiBodyConstraintSolver.h

@@ -49,7 +49,7 @@ protected:
 
 	void convertContacts(btPersistentManifold * *manifoldPtr, int numManifolds, const btContactSolverInfo& infoGlobal);
 
-	btMultiBodySolverConstraint& addMultiBodyFrictionConstraint(const btVector3& normalAxis, btPersistentManifold* manifold, int frictionIndex, btManifoldPoint& cp, btCollisionObject* colObj0, btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity = 0, btScalar cfmSlip = 0);
+	btMultiBodySolverConstraint& addMultiBodyFrictionConstraint(const btVector3& normalAxis, const btScalar& appliedImpulse, btPersistentManifold* manifold, int frictionIndex, btManifoldPoint& cp, btCollisionObject* colObj0, btCollisionObject* colObj1, btScalar relaxation, const btContactSolverInfo& infoGlobal, btScalar desiredVelocity = 0, btScalar cfmSlip = 0);
 
 	btMultiBodySolverConstraint& addMultiBodyTorsionalFrictionConstraint(const btVector3& normalAxis, btPersistentManifold* manifold, int frictionIndex, btManifoldPoint& cp,
 																		 btScalar combinedTorsionalFriction,
@@ -66,7 +66,9 @@ protected:
 
 	void setupMultiBodyContactConstraint(btMultiBodySolverConstraint & solverConstraint,
 										 const btVector3& contactNormal,
-										 btManifoldPoint& cp, const btContactSolverInfo& infoGlobal,
+                     const btScalar& appliedImpulse,
+										 btManifoldPoint& cp,
+                     const btContactSolverInfo& infoGlobal,
 										 btScalar& relaxation,
 										 bool isFriction, btScalar desiredVelocity = 0, btScalar cfmSlip = 0);
 
@@ -82,7 +84,6 @@ protected:
 	void convertMultiBodyContact(btPersistentManifold * manifold, const btContactSolverInfo& infoGlobal);
 	virtual btScalar solveGroupCacheFriendlySetup(btCollisionObject * *bodies, int numBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer);
 	//	virtual btScalar solveGroupCacheFriendlyIterations(btCollisionObject** bodies,int numBodies,btPersistentManifold** manifoldPtr, int numManifolds,btTypedConstraint** constraints,int numConstraints,const btContactSolverInfo& infoGlobal,btIDebugDraw* debugDrawer);
-
 	virtual btScalar solveSingleIteration(int iteration, btCollisionObject** bodies, int numBodies, btPersistentManifold** manifoldPtr, int numManifolds, btTypedConstraint** constraints, int numConstraints, const btContactSolverInfo& infoGlobal, btIDebugDraw* debugDrawer);
 	void applyDeltaVee(btScalar * deltaV, btScalar impulse, int velocityIndex, int ndof);
 	void writeBackSolverBodyToMultiBody(btMultiBodySolverConstraint & constraint, btScalar deltaTime);