revert previous cmake copy->symlink (doesn't work on Windows)

fix timing issues at small timestep, disable default linear damping for btMultiBody

examples/ExampleBrowser/CMakeLists.txt

@@ -378,11 +378,12 @@ ADD_EXECUTABLE(App_ExampleBrowser
 		${BulletExampleBrowser_SRCS} 
 )
 
+FILE( MAKE_DIRECTORY "${PROJECT_BINARY_DIR}/data" )
 
 ADD_CUSTOM_COMMAND(
                 TARGET App_ExampleBrowser
                 POST_BUILD
-                COMMAND ${CMAKE_COMMAND} ARGS -E create_symlink ${BULLET_PHYSICS_SOURCE_DIR}/data ${PROJECT_BINARY_DIR}/data
+                COMMAND ${CMAKE_COMMAND} ARGS -E copy_directory ${BULLET_PHYSICS_SOURCE_DIR}/data ${PROJECT_BINARY_DIR}/data
         )
 
 IF (BULLET2_MULTITHREADED_TBB_DEMO AND WIN32)

examples/SharedMemory/PhysicsServerExample.cpp

@@ -305,6 +305,7 @@ void	MotionThreadFunc(void* userPtr,void* lsMemory)
 
 		double deltaTimeInSeconds = 0;
 		int numCmdSinceSleep1ms = 0;
+		unsigned long long int prevTime = clock.getTimeMicroseconds();
 		
 		do
 		{
@@ -330,8 +331,16 @@ void	MotionThreadFunc(void* userPtr,void* lsMemory)
 				sleepClock.reset();
 				numCmdSinceSleep1ms = 0;
 			}
+
+			unsigned long long int curTime = clock.getTimeMicroseconds();
+			unsigned long long int dtMicro = curTime - prevTime;
+			prevTime = curTime;
+#if 1
+			double dt = double(dtMicro)/1000000.;
+#else
 			double dt = double(clock.getTimeMicroseconds())/1000000.;
 			clock.reset();
+#endif
 			deltaTimeInSeconds+= dt;
 			
 			{

src/BulletDynamics/Featherstone/btMultiBody.cpp

@@ -112,7 +112,7 @@ btMultiBody::btMultiBody(int n_links,
 		m_userObjectPointer(0),
 		m_userIndex2(-1),
 		m_userIndex(-1),
-		m_linearDamping(0.04f),
+		m_linearDamping(0.0f),
 		m_angularDamping(0.04f),
 		m_useGyroTerm(true),
 			m_maxAppliedImpulse(1000.f),