fixes to allow applying impulses during interpolated timesteps (avoid visual discontinuities)

experimental jitter removal (doesn't work very well yet)

src/BulletCollision/CollisionDispatch/btCollisionObject.h

@@ -43,6 +43,11 @@ struct	btCollisionObject
 	///m_interpolationWorldTransform is used for CCD and interpolation
 	///it can be either previous or future (predicted) transform
 	btTransform	m_interpolationWorldTransform;
+	//those two are experimental: just added for bullet time effect, so you can still apply impulses (directly modifying velocities) 
+	//without destroying the continuous interpolated motion (which uses this interpolation velocities)
+	btVector3	m_interpolationLinearVelocity;
+	btVector3	m_interpolationAngularVelocity;
+
 
 	enum CollisionFlags
 	{

src/BulletDynamics/Dynamics/btDiscreteDynamicsWorld.cpp

@@ -150,7 +150,8 @@ void	btDiscreteDynamicsWorld::synchronizeMotionStates()
 			if (body->GetActivationState() != ISLAND_SLEEPING)
 			{
 				btTransform interpolatedTransform;
-				btTransformUtil::integrateTransform(body->m_interpolationWorldTransform,body->getLinearVelocity(),body->getAngularVelocity(),m_localTime,interpolatedTransform);
+				btTransformUtil::integrateTransform(body->m_interpolationWorldTransform,
+					body->m_interpolationLinearVelocity,body->m_interpolationAngularVelocity,m_localTime,interpolatedTransform);
 				body->getMotionState()->setWorldTransform(interpolatedTransform);
 			}
 		}

src/BulletDynamics/Dynamics/btRigidBody.cpp

@@ -45,7 +45,9 @@ btRigidBody::btRigidBody(float mass, btMotionState* motionState, btCollisionShap
 	motionState->getWorldTransform(m_worldTransform);
 
 	m_interpolationWorldTransform = m_worldTransform;
-
+	m_interpolationLinearVelocity.setValue(0,0,0);
+	m_interpolationAngularVelocity.setValue(0,0,0);
+	
 	//moved to btCollisionObject
 	m_friction = friction;
 	m_restitution = restitution;
@@ -79,6 +81,8 @@ btRigidBody::btRigidBody( float mass,const btTransform& worldTransform,btCollisi
 	
 	m_worldTransform = worldTransform;
 	m_interpolationWorldTransform = m_worldTransform;
+	m_interpolationLinearVelocity.setValue(0,0,0);
+	m_interpolationAngularVelocity.setValue(0,0,0);
 
 	//moved to btCollisionObject
 	m_friction = friction;
@@ -96,12 +100,32 @@ btRigidBody::btRigidBody( float mass,const btTransform& worldTransform,btCollisi
 
 }
 
+#define EXPERIMENTAL_JITTER_REMOVAL 1
+#ifdef EXPERIMENTAL_JITTER_REMOVAL
+//Bullet 2.20b has experimental code to reduce jitter just before objects fall asleep/deactivate
+//doesn't work very well yet (value 0 only reduces performance a bit, no difference in functionality)
+float gClippedAngvelThresholdSqr = 0.f;
+float	gClippedLinearThresholdSqr = 0.f;
+#endif //EXPERIMENTAL_JITTER_REMOVAL
 
-
+void btRigidBody::predictIntegratedTransform(btScalar timeStep,btTransform& predictedTransform) 
-
-
-void btRigidBody::predictIntegratedTransform(btScalar timeStep,btTransform& predictedTransform) const
 {
+
+#ifdef EXPERIMENTAL_JITTER_REMOVAL
+	//clip to avoid jitter
+	if (m_angularVelocity.length2() < gClippedAngvelThresholdSqr)
+	{
+		m_angularVelocity.setValue(0,0,0);
+		printf("clipped!\n");
+	}
+	
+	if (m_linearVelocity.length2() < gClippedLinearThresholdSqr)
+	{
+		m_linearVelocity.setValue(0,0,0);
+		printf("clipped!\n");
+	}
+#endif //EXPERIMENTAL_JITTER_REMOVAL
+
 	btTransformUtil::integrateTransform(m_worldTransform,m_linearVelocity,m_angularVelocity,timeStep,predictedTransform);
 }
 
@@ -114,7 +138,10 @@ void			btRigidBody::saveKinematicState(btScalar timeStep)
 		if (getMotionState())
 			getMotionState()->getWorldTransform(m_worldTransform);
 		btVector3 linVel,angVel;
+		
 		btTransformUtil::calculateVelocity(m_interpolationWorldTransform,m_worldTransform,timeStep,m_linearVelocity,m_angularVelocity);
+		m_interpolationLinearVelocity = m_linearVelocity;
+		m_interpolationAngularVelocity = m_angularVelocity;
 		m_interpolationWorldTransform = m_worldTransform;
 		//printf("angular = %f %f %f\n",m_angularVelocity.getX(),m_angularVelocity.getY(),m_angularVelocity.getZ());
 	}
@@ -257,6 +284,8 @@ btQuaternion btRigidBody::getOrientation() const
 void btRigidBody::setCenterOfMassTransform(const btTransform& xform)
 {
 	m_interpolationWorldTransform = m_worldTransform;
+	m_interpolationLinearVelocity = getLinearVelocity();
+	m_interpolationAngularVelocity = getAngularVelocity();
 	m_worldTransform = xform;
 	updateInertiaTensor();
 }

src/BulletDynamics/Dynamics/btRigidBody.h

@@ -79,7 +79,7 @@ public:
 	}
 	
 	/// continuous collision detection needs prediction
-	void			predictIntegratedTransform(btScalar step, btTransform& predictedTransform) const;
+	void			predictIntegratedTransform(btScalar step, btTransform& predictedTransform) ;
 	
 	void			saveKinematicState(btScalar step);