diff --git a/docs/pybullet_quickstartguide.pdf b/docs/pybullet_quickstartguide.pdf
index 869773630..8f49ec179 100644
Binary files a/docs/pybullet_quickstartguide.pdf and b/docs/pybullet_quickstartguide.pdf differ
diff --git a/examples/Importers/ImportColladaDemo/LoadMeshFromCollada.cpp b/examples/Importers/ImportColladaDemo/LoadMeshFromCollada.cpp
index 8a99da00f..348b96d7c 100644
--- a/examples/Importers/ImportColladaDemo/LoadMeshFromCollada.cpp
+++ b/examples/Importers/ImportColladaDemo/LoadMeshFromCollada.cpp
@@ -336,9 +336,7 @@ void readLibraryGeometries(TiXmlDocument& doc, btAlignedObjectArray<GLInstanceGr
 
 void readNodeHierarchy(TiXmlElement* node,btHashMap<btHashString,int>& name2Shape, btAlignedObjectArray<ColladaGraphicsInstance>& visualShapeInstances,  const btMatrix4x4& parentTransMat)
 {
-	//const char* nodeName = node->Attribute("id");
-	//printf("processing node %s\n", nodeName);
-
+	
 	
 	btMatrix4x4 nodeTrans;
 	nodeTrans.setIdentity();
diff --git a/examples/OpenGLWindow/MacOpenGLWindow.mm b/examples/OpenGLWindow/MacOpenGLWindow.mm
index 0f0d07ec4..80a11fc1b 100644
--- a/examples/OpenGLWindow/MacOpenGLWindow.mm
+++ b/examples/OpenGLWindow/MacOpenGLWindow.mm
@@ -10,6 +10,61 @@
 #include <stddef.h>
 #include <string.h>
 
+#include <Availability.h>
+
+
+//aargh, Mac OSX 10.12 broke backwards compatibility, fix it here for now
+#ifdef __MAC_10_12
+    #define MyNSTitledWindowMask NSWindowStyleMaskTitled
+    #define MyNSResizableWindowMask NSWindowStyleMaskResizable
+    #define MyNSClosableWindowMask NSWindowStyleMaskClosable
+    #define MyNSMiniaturizableWindowMask NSWindowStyleMaskMiniaturizable
+    #define MyNSAnyEventMask NSEventMaskAny
+    #define MyNSEventTypeFlagsChanged NSEventTypeFlagsChanged
+    #define MyNSEventModifierFlagShift NSEventModifierFlagShift
+    #define MyNSEventModifierFlagControl NSEventModifierFlagControl
+    #define MyNSEventModifierFlagOption NSEventModifierFlagOption
+    #define MyNSKeyUp NSEventTypeKeyUp
+    #define MyNSKeyDown NSEventTypeKeyDown
+    #define MyNSRightMouseDown NSEventTypeRightMouseDown
+    #define MyNSLeftMouseDown NSEventTypeLeftMouseDown
+    #define MyNSOtherMouseDown NSEventTypeOtherMouseDown
+    #define MyNSRightMouseUp NSEventTypeRightMouseUp
+    #define MyNSLeftMouseUp NSEventTypeLeftMouseUp
+    #define MyNSOtherMouseUp NSEventTypeOtherMouseUp
+    #define MyNSMouseMoved NSEventTypeMouseMoved
+    #define MyNSLeftMouseDragged NSEventTypeLeftMouseDragged
+    #define MyNSRightMouseDragged NSEventTypeRightMouseDragged
+    #define MyNSOtherMouseDragged NSEventTypeOtherMouseDragged
+    #define MyNSScrollWheel NSEventTypeScrollWheel
+
+
+#else
+    #define MyNSTitledWindowMask NSTitledWindowMask
+    #define MyNSResizableWindowMask NSResizableWindowMask
+    #define MyNSClosableWindowMask NSClosableWindowMask
+    #define MyNSMiniaturizableWindowMask NSMiniaturizableWindowMask
+    #define MyNSAnyEventMask NSAnyEventMask
+    #define MyNSEventTypeFlagsChanged NSFlagsChanged
+    #define MyNSEventModifierFlagShift NSShiftKeyMask
+    #define MyNSEventModifierFlagControl NSControlKeyMask
+    #define MyNSEventModifierFlagOption NSAlternateKeyMask
+    #define MyNSKeyUp NSKeyUp
+    #define MyNSKeyDown NSKeyDown
+    #define NSRightMouseDown NSRightMouseDown
+    #define MyNSLeftMouseDown LeftMouseDown
+    #define MyNSOtherMouseDown NSOtherMouseDown
+    #define MyNSLeftMouseUp NSLeftMouseUp
+    #define MyNSRightMouseUp NSRightMouseUp
+    #define MyNSOtherMouseUp NSOtherMouseUp
+    #define MyNSMouseMoved NSMouseMoved
+    #define MyNSLeftMouseDragged NSLeftMouseDragged
+    #define MyNSRightMouseDragged NSRightMouseDragged
+    #define MyNSOtherMouseDragged NSOtherMouseDragged
+    #define MyNSScrollWheel NSScrollWheel
+
+
+#endif
 
 enum
 {
@@ -368,7 +423,7 @@ void MacOpenGLWindow::createWindow(const b3gWindowConstructionInfo& ci)
 	
 	m_internalData->m_window = [NSWindow alloc];
 	[m_internalData->m_window initWithContentRect:frame
-                      styleMask:NSTitledWindowMask |NSResizableWindowMask| NSClosableWindowMask | NSMiniaturizableWindowMask
+                      styleMask:MyNSTitledWindowMask |MyNSResizableWindowMask| MyNSClosableWindowMask | MyNSMiniaturizableWindowMask
                         backing:NSBackingStoreBuffered
                           defer:false];
 	
@@ -771,7 +826,7 @@ void MacOpenGLWindow::startRendering()
         [pool release];
         pool = [[NSAutoreleasePool alloc] init];
         event =        [m_internalData->m_myApp
-         nextEventMatchingMask:NSAnyEventMask
+         nextEventMatchingMask:MyNSAnyEventMask
          untilDate:[NSDate distantPast]
          inMode:NSDefaultRunLoopMode
          //		  inMode:NSEventTrackingRunLoopMode
@@ -780,12 +835,12 @@ void MacOpenGLWindow::startRendering()
 		//NSShiftKeyMask              = 1 << 17,
 		//NSControlKeyMask
 	
-		if ([event type] == NSFlagsChanged)
+		if ([event type] == MyNSEventTypeFlagsChanged)
 		{
 			int modifiers = [event modifierFlags];
 			if (m_keyboardCallback)
 			{
-				if ((modifiers & NSShiftKeyMask))
+				if ((modifiers & MyNSEventModifierFlagShift))
 				{
 					m_keyboardCallback(B3G_SHIFT,1);
 					m_modifierFlags |= MY_MAC_SHIFTKEY;
@@ -797,7 +852,7 @@ void MacOpenGLWindow::startRendering()
 						m_modifierFlags &= ~MY_MAC_SHIFTKEY;
 					}
 				}
-				if (modifiers & NSControlKeyMask)
+				if (modifiers & MyNSEventModifierFlagControl)
 				{
 					m_keyboardCallback(B3G_CONTROL,1);
 					m_modifierFlags |= MY_MAC_CONTROL_KEY;
@@ -809,7 +864,7 @@ void MacOpenGLWindow::startRendering()
 						m_modifierFlags &= ~MY_MAC_CONTROL_KEY;
 					}
 				}
-				if (modifiers & NSAlternateKeyMask)
+				if (modifiers & MyNSEventModifierFlagOption)
 				{
 					m_keyboardCallback(B3G_ALT,1);
 					m_modifierFlags |= MY_MAC_ALTKEY;
@@ -826,7 +881,7 @@ void MacOpenGLWindow::startRendering()
 				
 			}
 		}
-		if ([event type] == NSKeyUp)
+		if ([event type] == MyNSKeyUp)
         {
 			handledEvent = true;
 			
@@ -841,7 +896,9 @@ void MacOpenGLWindow::startRendering()
 				m_keyboardCallback(keycode,state);
 			}
 		}
-        if ([event type] == NSKeyDown)
+
+        
+        if ([event type] == MyNSKeyDown)
         {
 			handledEvent = true;
 			
@@ -861,7 +918,8 @@ void MacOpenGLWindow::startRendering()
 		}
 
 
-        if (([event type]== NSRightMouseDown) || ([ event type]==NSLeftMouseDown)||([event type]==NSOtherMouseDown))
+        
+        if (([event type]== MyNSRightMouseDown) || ([ event type]==MyNSLeftMouseDown)||([event type]==MyNSOtherMouseDown))
         {
            // printf("right mouse!");
           //  float mouseX,mouseY;
@@ -873,17 +931,17 @@ void MacOpenGLWindow::startRendering()
             int button=0;
 	        switch ([event type])
             {
-                case NSLeftMouseDown:
+                case MyNSLeftMouseDown:
                 {
                     button=0;
                     break;
                 }
-                case NSOtherMouseDown:
+                case MyNSOtherMouseDown:
                 {
                     button=1;
                     break;
                 }
-                case NSRightMouseDown:
+                case MyNSRightMouseDown:
                 {
                     button=2;
                     break;
@@ -902,7 +960,7 @@ void MacOpenGLWindow::startRendering()
         }
 		
 		
-        if (([event type]== NSRightMouseUp) || ([ event type]==NSLeftMouseUp)||([event type]==NSOtherMouseUp))
+        if (([event type]== MyNSRightMouseUp) || ([ event type]==MyNSLeftMouseUp)||([event type]==MyNSOtherMouseUp))
         {
 			// printf("right mouse!");
 			//  float mouseX,mouseY;
@@ -915,17 +973,17 @@ void MacOpenGLWindow::startRendering()
             int button=0;
             switch ([event type])
             {
-                case NSLeftMouseUp:
+                case MyNSLeftMouseUp:
                 {
                     button=0;
                     break;
                 }
-                case NSOtherMouseUp:
+                case MyNSOtherMouseUp:
                 {
                     button=1;
                     break;
                 }
-                case NSRightMouseUp:
+                case MyNSRightMouseUp:
                 {
                     button=2;
                     break;
@@ -943,7 +1001,7 @@ void MacOpenGLWindow::startRendering()
         }
 		
         
-        if ([event type] == NSMouseMoved)
+        if ([event type] == MyNSMouseMoved)
         {
             
             NSPoint eventLocation = [event locationInWindow];
@@ -960,7 +1018,8 @@ void MacOpenGLWindow::startRendering()
 			}
         }
         
-        if (([event type] == NSLeftMouseDragged) || ([event type] == NSRightMouseDragged) || ([event type] == NSOtherMouseDragged))
+        
+        if (([event type] == MyNSLeftMouseDragged) || ([event type] == MyNSRightMouseDragged) || ([event type] == MyNSOtherMouseDragged))
         {
             int dx1, dy1;
             CGGetLastMouseDelta (&dx1, &dy1);
@@ -979,7 +1038,7 @@ void MacOpenGLWindow::startRendering()
           //  printf("mouse coord = %f, %f\n",m_mouseX,m_mouseY);
         }
         
-        if ([event type] == NSScrollWheel)
+        if ([event type] == MyNSScrollWheel)
         {
             float dy, dx;
             dy = [ event deltaY ];
diff --git a/examples/SharedMemory/PhysicsClient.h b/examples/SharedMemory/PhysicsClient.h
index 3e3248a0b..1fdb07ad4 100644
--- a/examples/SharedMemory/PhysicsClient.h
+++ b/examples/SharedMemory/PhysicsClient.h
@@ -34,6 +34,10 @@ public:
 
     virtual bool getJointInfo(int bodyUniqueId, int jointIndex, struct b3JointInfo& info) const = 0;
 
+    virtual int getNumUserConstraints() const = 0;
+    
+    virtual int getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint& info) const = 0;
+    
     virtual void setSharedMemoryKey(int key) = 0;
 
     virtual void uploadBulletFileToSharedMemory(const char* data, int len) = 0;
diff --git a/examples/SharedMemory/PhysicsClientC_API.cpp b/examples/SharedMemory/PhysicsClientC_API.cpp
index 37e7cb78b..08be193e8 100644
--- a/examples/SharedMemory/PhysicsClientC_API.cpp
+++ b/examples/SharedMemory/PhysicsClientC_API.cpp
@@ -1045,6 +1045,31 @@ int	b3GetNumBodies(b3PhysicsClientHandle physClient)
 	return cl->getNumBodies();
 }
 
+int b3GetNumUserConstraints(b3PhysicsClientHandle physClient)
+{
+    PhysicsClient* cl = (PhysicsClient* ) physClient;
+    return cl->getNumUserConstraints();
+}
+
+int b3GetUserConstraintInfo(b3PhysicsClientHandle physClient, int constraintUniqueId, struct b3UserConstraint* infoPtr)
+{
+    PhysicsClient* cl = (PhysicsClient* ) physClient;
+    b3UserConstraint constraintInfo1;
+    b3Assert(physClient);
+    b3Assert(infoPtr);
+    b3Assert(constraintUniqueId>=0);
+    
+    if (infoPtr==0)
+        return 0;
+
+    if (cl->getUserConstraintInfo(constraintUniqueId, constraintInfo1))
+    {
+        *infoPtr = constraintInfo1;
+        return 1;
+    }
+    return 0;
+}
+
 /// return the body unique id, given the index in range [0 , b3GetNumBodies() )
 int b3GetBodyUniqueId(b3PhysicsClientHandle physClient, int serialIndex)
 {
diff --git a/examples/SharedMemory/PhysicsClientC_API.h b/examples/SharedMemory/PhysicsClientC_API.h
index 54f1ad1e1..dc972cfa1 100644
--- a/examples/SharedMemory/PhysicsClientC_API.h
+++ b/examples/SharedMemory/PhysicsClientC_API.h
@@ -57,7 +57,7 @@ int b3GetStatusActualState(b3SharedMemoryStatusHandle statusHandle,
                            const double* actualStateQdot[],
                            const double* jointReactionForces[]);
 
-///If you re-connected to an existing server, or server changed otherwise, sync the body info
+///If you re-connected to an existing server, or server changed otherwise, sync the body info and user constraints etc.
 b3SharedMemoryCommandHandle b3InitSyncBodyInfoCommand(b3PhysicsClientHandle physClient);
 
 ///return the total number of bodies in the simulation
@@ -76,15 +76,21 @@ int	b3GetNumJoints(b3PhysicsClientHandle physClient, int bodyIndex);
 int	b3GetJointInfo(b3PhysicsClientHandle physClient, int bodyIndex, int jointIndex, struct b3JointInfo* info);
     
 b3SharedMemoryCommandHandle b3InitCreateUserConstraintCommand(b3PhysicsClientHandle physClient, int parentBodyIndex, int parentJointIndex, int childBodyIndex, int childJointIndex, struct b3JointInfo* info);
+
+///return a unique id for the user constraint, after successful creation, or -1 for an invalid constraint id
 int b3GetStatusUserConstraintUniqueId(b3SharedMemoryStatusHandle statusHandle);
+
+///change parameters of an existing user constraint
 b3SharedMemoryCommandHandle  b3InitChangeUserConstraintCommand(b3PhysicsClientHandle physClient, int userConstraintUniqueId);
 int b3InitChangeUserConstraintSetPivotInB(b3SharedMemoryCommandHandle commandHandle, double jointChildPivot[3]);
 int b3InitChangeUserConstraintSetFrameInB(b3SharedMemoryCommandHandle commandHandle, double jointChildFrameOrn[4]);
 int b3InitChangeUserConstraintSetMaxForce(b3SharedMemoryCommandHandle commandHandle, double maxAppliedForce);
 	
-
 b3SharedMemoryCommandHandle  b3InitRemoveUserConstraintCommand(b3PhysicsClientHandle physClient, int userConstraintUniqueId);
 
+int b3GetNumUserConstraints(b3PhysicsClientHandle physClient);
+int b3GetUserConstraintInfo(b3PhysicsClientHandle physClient, int constraintUniqueId, struct b3UserConstraint* info);
+    
 ///Request physics debug lines for debug visualization. The flags in debugMode are the same as used in Bullet
 ///See btIDebugDraw::DebugDrawModes in Bullet/src/LinearMath/btIDebugDraw.h
 b3SharedMemoryCommandHandle b3InitRequestDebugLinesCommand(b3PhysicsClientHandle physClient, int debugMode);
@@ -320,7 +326,7 @@ void b3GetRaycastInformation(b3PhysicsClientHandle physClient, struct b3RaycastI
 b3SharedMemoryCommandHandle b3ApplyExternalForceCommandInit(b3PhysicsClientHandle physClient);
 void b3ApplyExternalForce(b3SharedMemoryCommandHandle commandHandle, int bodyUniqueId, int linkId, const double force[3], const double position[3], int flags);
 void b3ApplyExternalTorque(b3SharedMemoryCommandHandle commandHandle, int bodyUniqueId, int linkId, const double torque[3], int flags);
-    
+
 ///experiments of robots interacting with non-rigid objects (such as btSoftBody)
 b3SharedMemoryCommandHandle	b3LoadBunnyCommandInit(b3PhysicsClientHandle physClient);
 int b3LoadBunnySetScale(b3SharedMemoryCommandHandle commandHandle, double scale);
diff --git a/examples/SharedMemory/PhysicsClientSharedMemory.cpp b/examples/SharedMemory/PhysicsClientSharedMemory.cpp
index df2aed6a7..d635012a1 100644
--- a/examples/SharedMemory/PhysicsClientSharedMemory.cpp
+++ b/examples/SharedMemory/PhysicsClientSharedMemory.cpp
@@ -28,6 +28,7 @@ struct PhysicsClientSharedMemoryInternalData {
     SharedMemoryBlock* m_testBlock1;
    
 	btHashMap<btHashInt,BodyJointInfoCache*> m_bodyJointMap;
+	btHashMap<btHashInt,b3UserConstraint> m_userConstraintInfoMap;
 
     btAlignedObjectArray<TmpFloat3> m_debugLinesFrom;
     btAlignedObjectArray<TmpFloat3> m_debugLinesTo;
@@ -46,6 +47,8 @@ struct PhysicsClientSharedMemoryInternalData {
 	btAlignedObjectArray<b3RayHitInfo>	m_raycastHits;
 
     btAlignedObjectArray<int> m_bodyIdsRequestInfo;
+	btAlignedObjectArray<int> m_constraintIdsRequestInfo;
+
     SharedMemoryStatus m_tempBackupServerStatus;
     
     SharedMemoryStatus m_lastServerStatus;
@@ -138,6 +141,22 @@ bool PhysicsClientSharedMemory::getJointInfo(int bodyUniqueId, int jointIndex, b
     return false;
 }
 
+int PhysicsClientSharedMemory::getNumUserConstraints() const
+{
+    return m_data->m_userConstraintInfoMap.size();
+}
+
+int PhysicsClientSharedMemory::getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint& info) const
+{
+    b3UserConstraint* constraintPtr =m_data->m_userConstraintInfoMap[constraintUniqueId];
+    if (constraintPtr)
+    {
+        info = *constraintPtr;
+        return 1;
+    }
+    return 0;
+}
+
 PhysicsClientSharedMemory::PhysicsClientSharedMemory()
 
 {
@@ -156,6 +175,8 @@ PhysicsClientSharedMemory::~PhysicsClientSharedMemory() {
     if (m_data->m_isConnected) {
         disconnectSharedMemory();
     }
+	resetData();
+
 	if (m_data->m_ownsSharedMemory)
 	{
 	    delete m_data->m_sharedMemory;
@@ -163,6 +184,34 @@ PhysicsClientSharedMemory::~PhysicsClientSharedMemory() {
     delete m_data;
 }
 
+void PhysicsClientSharedMemory::resetData()
+{
+	m_data->m_debugLinesFrom.clear();
+	m_data->m_debugLinesTo.clear();
+	m_data->m_debugLinesColor.clear();
+	for (int i=0;i<m_data->m_bodyJointMap.size();i++)
+	{
+		BodyJointInfoCache** bodyJointsPtr = m_data->m_bodyJointMap.getAtIndex(i);
+		if (bodyJointsPtr && *bodyJointsPtr)
+		{
+			BodyJointInfoCache* bodyJoints = *bodyJointsPtr;
+			for (int j=0;j<bodyJoints->m_jointInfo.size();j++) {
+				if (bodyJoints->m_jointInfo[j].m_jointName)
+				{
+					free(bodyJoints->m_jointInfo[j].m_jointName);
+				}
+				if (bodyJoints->m_jointInfo[j].m_linkName)
+				{
+					free(bodyJoints->m_jointInfo[j].m_linkName);
+				}
+			}
+			delete (*bodyJointsPtr);
+		}
+	}
+	m_data->m_bodyJointMap.clear();
+	m_data->m_userConstraintInfoMap.clear();
+                
+}
 void PhysicsClientSharedMemory::setSharedMemoryKey(int key) { m_data->m_sharedMemoryKey = key; }
 
 
@@ -398,7 +447,72 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
                 
                 break;
             }
-            
+			case CMD_USER_CONSTRAINT_INFO_COMPLETED:
+			{
+				 int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+				m_data->m_userConstraintInfoMap.insert(cid,serverCmd.m_userConstraintResultArgs);
+				break;
+			}
+			case CMD_USER_CONSTRAINT_COMPLETED:
+			{
+				int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+				m_data->m_userConstraintInfoMap.insert(cid,serverCmd.m_userConstraintResultArgs);
+				break;
+			}
+			case CMD_REMOVE_USER_CONSTRAINT_COMPLETED:
+			{
+				int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+				m_data->m_userConstraintInfoMap.remove(cid);
+				break;
+			}
+			case CMD_CHANGE_USER_CONSTRAINT_COMPLETED:
+			{
+				int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+				b3UserConstraint* userConstraintPtr = m_data->m_userConstraintInfoMap[cid];
+				if (userConstraintPtr)
+				{
+					const b3UserConstraint* serverConstraint = &serverCmd.m_userConstraintResultArgs;
+					if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_PIVOT_IN_B)
+					{
+							userConstraintPtr->m_childFrame[0] = serverConstraint->m_childFrame[0];
+							userConstraintPtr->m_childFrame[1] = serverConstraint->m_childFrame[1];
+							userConstraintPtr->m_childFrame[2] = serverConstraint->m_childFrame[2];
+					}
+					if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_FRAME_ORN_IN_B)
+					{
+						userConstraintPtr->m_childFrame[3] = serverConstraint->m_childFrame[3];
+						userConstraintPtr->m_childFrame[4] = serverConstraint->m_childFrame[4];
+						userConstraintPtr->m_childFrame[5] = serverConstraint->m_childFrame[5];
+						userConstraintPtr->m_childFrame[6] = serverConstraint->m_childFrame[6];
+					}
+					if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_MAX_FORCE)
+					{
+						userConstraintPtr->m_maxAppliedForce = serverConstraint->m_maxAppliedForce;
+					}
+				}
+				break;
+			}
+
+			case CMD_USER_CONSTRAINT_FAILED:
+			{
+				b3Warning("createConstraint failed");
+				break;
+			}
+			case CMD_REMOVE_USER_CONSTRAINT_FAILED:
+			{
+				b3Warning("removeConstraint failed");
+				break;
+			}
+			case CMD_CHANGE_USER_CONSTRAINT_FAILED:
+			{
+				b3Warning("changeConstraint failed");
+				break;
+			}
+			case CMD_ACTUAL_STATE_UPDATE_FAILED:
+			{
+				b3Warning("request actual state failed");
+				break;
+			}
             case CMD_BODY_INFO_COMPLETED:
             {
                 if (m_data->m_verboseOutput) {
@@ -497,30 +611,8 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
                 if (m_data->m_verboseOutput) {
                     b3Printf("CMD_RESET_SIMULATION_COMPLETED clean data\n");
                 }
-				m_data->m_debugLinesFrom.clear();
-				m_data->m_debugLinesTo.clear();
-				m_data->m_debugLinesColor.clear();
-                for (int i=0;i<m_data->m_bodyJointMap.size();i++)
-				{
-					BodyJointInfoCache** bodyJointsPtr = m_data->m_bodyJointMap.getAtIndex(i);
-					if (bodyJointsPtr && *bodyJointsPtr)
-					{
-						BodyJointInfoCache* bodyJoints = *bodyJointsPtr;
-						for (int j=0;j<bodyJoints->m_jointInfo.size();j++) {
-							if (bodyJoints->m_jointInfo[j].m_jointName)
-							{
-								free(bodyJoints->m_jointInfo[j].m_jointName);
-							}
-							if (bodyJoints->m_jointInfo[j].m_linkName)
-							{
-								free(bodyJoints->m_jointInfo[j].m_linkName);
-							}
-						}
-						delete (*bodyJointsPtr);
-					}
-				}
-				m_data->m_bodyJointMap.clear();
-                
+				resetData();
+
                 break;
             }
             case CMD_DEBUG_LINES_COMPLETED: {
@@ -802,20 +894,7 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
 				b3Warning("User debug draw failed");
 				break;
 			}
-			case CMD_USER_CONSTRAINT_COMPLETED:
-			{
-				break;
-			}
-			case CMD_USER_CONSTRAINT_FAILED:
-			{
-				b3Warning("createConstraint failed");
-				break;
-			}
-			case CMD_ACTUAL_STATE_UPDATE_FAILED:
-			{
-				b3Warning("request actual state failed");
-				break;
-			}
+			
 			case CMD_SYNC_BODY_INFO_COMPLETED:
 			{
 				break;
@@ -841,6 +920,12 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
 
         if ((serverCmd.m_type == CMD_SDF_LOADING_COMPLETED) || (serverCmd.m_type == CMD_MJCF_LOADING_COMPLETED) || (serverCmd.m_type == CMD_SYNC_BODY_INFO_COMPLETED))
         {
+			int numConstraints = serverCmd.m_sdfLoadedArgs.m_numUserConstraints;
+			for (int i=0;i<numConstraints;i++)
+			{
+				int constraintUid = serverCmd.m_sdfLoadedArgs.m_userConstraintUniqueIds[i];
+				m_data->m_constraintIdsRequestInfo.push_back(constraintUid);
+			}
             int numBodies = serverCmd.m_sdfLoadedArgs.m_numBodies;
             if (numBodies>0)
             {
@@ -863,6 +948,25 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
             }
         }
         
+		if (serverCmd.m_type == CMD_USER_CONSTRAINT_INFO_COMPLETED)
+		{
+			if (m_data->m_constraintIdsRequestInfo.size())
+			{
+				int cid = m_data->m_constraintIdsRequestInfo[m_data->m_constraintIdsRequestInfo.size()-1];
+				m_data->m_constraintIdsRequestInfo.pop_back();
+				SharedMemoryCommand& command = m_data->m_testBlock1->m_clientCommands[0];
+				command.m_type = CMD_USER_CONSTRAINT;
+				command.m_updateFlags = USER_CONSTRAINT_REQUEST_INFO;
+				command.m_userConstraintArguments.m_userConstraintUniqueId = cid;
+				submitClientCommand(command);
+				return 0;
+			} 
+			else
+			{
+	            m_data->m_lastServerStatus = m_data->m_tempBackupServerStatus;
+			}
+		}
+
         if (serverCmd.m_type == CMD_BODY_INFO_COMPLETED)
         {
             //are there any bodies left to be processed?
@@ -879,7 +983,20 @@ const SharedMemoryStatus* PhysicsClientSharedMemory::processServerStatus() {
                 return 0;
             } else
             {
-                m_data->m_lastServerStatus = m_data->m_tempBackupServerStatus;
+				if (m_data->m_constraintIdsRequestInfo.size())
+				{
+					int cid = m_data->m_constraintIdsRequestInfo[m_data->m_constraintIdsRequestInfo.size()-1];
+					m_data->m_constraintIdsRequestInfo.pop_back();
+					SharedMemoryCommand& command = m_data->m_testBlock1->m_clientCommands[0];
+					command.m_type = CMD_USER_CONSTRAINT;
+					command.m_updateFlags = USER_CONSTRAINT_REQUEST_INFO;
+					command.m_userConstraintArguments.m_userConstraintUniqueId = cid;
+					submitClientCommand(command);
+					return 0;
+				} else
+				{
+	                m_data->m_lastServerStatus = m_data->m_tempBackupServerStatus;
+				}
             }
         }
 
diff --git a/examples/SharedMemory/PhysicsClientSharedMemory.h b/examples/SharedMemory/PhysicsClientSharedMemory.h
index 854618456..57392d2b2 100644
--- a/examples/SharedMemory/PhysicsClientSharedMemory.h
+++ b/examples/SharedMemory/PhysicsClientSharedMemory.h
@@ -12,8 +12,8 @@ class PhysicsClientSharedMemory : public PhysicsClient {
 protected:
 	virtual void setSharedMemoryInterface(class SharedMemoryInterface* sharedMem);
     void processBodyJointInfo(int bodyUniqueId, const struct SharedMemoryStatus& serverCmd);
-    
-        
+    void resetData();
+
 public:
     PhysicsClientSharedMemory();
     virtual ~PhysicsClientSharedMemory();
@@ -44,6 +44,10 @@ public:
 
     virtual bool getJointInfo(int bodyUniqueId, int jointIndex, struct b3JointInfo& info) const;
 
+    virtual int getNumUserConstraints() const;
+    
+    virtual int getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint& info) const;
+    
     virtual void setSharedMemoryKey(int key);
 
     virtual void uploadBulletFileToSharedMemory(const char* data, int len);
diff --git a/examples/SharedMemory/PhysicsDirect.cpp b/examples/SharedMemory/PhysicsDirect.cpp
index 07dc561af..240cad4d1 100644
--- a/examples/SharedMemory/PhysicsDirect.cpp
+++ b/examples/SharedMemory/PhysicsDirect.cpp
@@ -19,6 +19,8 @@ struct BodyJointInfoCache2
 	btAlignedObjectArray<b3JointInfo> m_jointInfo;
 };
 
+
+
 struct PhysicsDirectInternalData
 {
 	DummyGUIHelper m_noGfx;
@@ -34,6 +36,7 @@ struct PhysicsDirectInternalData
     btAlignedObjectArray<TmpFloat3> m_debugLinesColor;
 
 	btHashMap<btHashInt,BodyJointInfoCache2*> m_bodyJointMap;
+    btHashMap<btHashInt,b3UserConstraint> m_userConstraintInfoMap;
 	
 	char    m_bulletStreamDataServerToClient[SHARED_MEMORY_MAX_STREAM_CHUNK_SIZE];
 
@@ -112,6 +115,7 @@ void PhysicsDirect::resetData()
 		}
 	}
 	m_data->m_bodyJointMap.clear();
+	m_data->m_userConstraintInfoMap.clear();
 }
 
 // return true if connection succesfull, can also check 'isConnected'
@@ -670,6 +674,47 @@ void PhysicsDirect::postProcessStatus(const struct SharedMemoryStatus& serverCmd
 		break;
 	}
 
+	case CMD_USER_CONSTRAINT_INFO_COMPLETED:
+    case CMD_USER_CONSTRAINT_COMPLETED:
+    {
+        int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+        m_data->m_userConstraintInfoMap.insert(cid,serverCmd.m_userConstraintResultArgs);
+        break;
+    }
+    case CMD_REMOVE_USER_CONSTRAINT_COMPLETED:
+    {
+        int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+        m_data->m_userConstraintInfoMap.remove(cid);
+        break;
+    }
+	case CMD_CHANGE_USER_CONSTRAINT_COMPLETED:
+	{
+        int cid = serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId;
+		b3UserConstraint* userConstraintPtr = m_data->m_userConstraintInfoMap[cid];
+		if (userConstraintPtr)
+		{
+			const b3UserConstraint* serverConstraint = &serverCmd.m_userConstraintResultArgs;
+			if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_PIVOT_IN_B)
+			{
+					userConstraintPtr->m_childFrame[0] = serverConstraint->m_childFrame[0];
+					userConstraintPtr->m_childFrame[1] = serverConstraint->m_childFrame[1];
+					userConstraintPtr->m_childFrame[2] = serverConstraint->m_childFrame[2];
+			}
+			if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_FRAME_ORN_IN_B)
+			{
+				userConstraintPtr->m_childFrame[3] = serverConstraint->m_childFrame[3];
+				userConstraintPtr->m_childFrame[4] = serverConstraint->m_childFrame[4];
+				userConstraintPtr->m_childFrame[5] = serverConstraint->m_childFrame[5];
+				userConstraintPtr->m_childFrame[6] = serverConstraint->m_childFrame[6];
+			}
+			if (serverCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_MAX_FORCE)
+			{
+				userConstraintPtr->m_maxAppliedForce = serverConstraint->m_maxAppliedForce;
+			}
+		}
+		break;
+	}
+
 	case CMD_SYNC_BODY_INFO_COMPLETED:
 	case CMD_MJCF_LOADING_COMPLETED:
 	case CMD_SDF_LOADING_COMPLETED:
@@ -677,6 +722,29 @@ void PhysicsDirect::postProcessStatus(const struct SharedMemoryStatus& serverCmd
 		//we'll stream further info from the physics server
 		//so serverCmd will be invalid, make a copy
 
+		int numConstraints = serverCmd.m_sdfLoadedArgs.m_numUserConstraints;
+		for (int i=0;i<numConstraints;i++)
+		{
+			int constraintUid = serverCmd.m_sdfLoadedArgs.m_userConstraintUniqueIds[i];
+			SharedMemoryCommand infoRequestCommand;
+			infoRequestCommand.m_type = CMD_USER_CONSTRAINT;
+			infoRequestCommand.m_updateFlags = USER_CONSTRAINT_REQUEST_INFO;
+			SharedMemoryStatus infoStatus;
+			bool hasStatus = m_data->m_commandProcessor->processCommand(infoRequestCommand, infoStatus, &m_data->m_bulletStreamDataServerToClient[0], SHARED_MEMORY_MAX_STREAM_CHUNK_SIZE);
+					
+
+			int timeout = 1024 * 1024 * 1024;
+			while ((!hasStatus) && (timeout-- > 0))
+			{
+				hasStatus = m_data->m_commandProcessor->receiveStatus(infoStatus, &m_data->m_bulletStreamDataServerToClient[0], SHARED_MEMORY_MAX_STREAM_CHUNK_SIZE);
+			}
+
+			if (hasStatus)
+			{
+				int cid = infoStatus.m_userConstraintResultArgs.m_userConstraintUniqueId;
+				m_data->m_userConstraintInfoMap.insert(cid,infoStatus.m_userConstraintResultArgs);
+			}
+		}
 
 		int numBodies = serverCmd.m_sdfLoadedArgs.m_numBodies;
 		for (int i = 0; i<numBodies; i++)
@@ -721,10 +789,18 @@ void PhysicsDirect::postProcessStatus(const struct SharedMemoryStatus& serverCmd
 	{
 		break;
 	}
-	case CMD_USER_CONSTRAINT_COMPLETED:
+	
+	case CMD_REMOVE_USER_CONSTRAINT_FAILED:
 	{
+		b3Warning("removeConstraint failed");
 		break;
 	}
+	case CMD_CHANGE_USER_CONSTRAINT_FAILED:
+	{
+		b3Warning("changeConstraint failed");
+		break;
+	}
+
 	case CMD_USER_CONSTRAINT_FAILED:
 	{
 		b3Warning("createConstraint failed");
@@ -765,10 +841,12 @@ bool PhysicsDirect::submitClientCommand(const struct SharedMemoryCommand& comman
 
 	bool hasStatus = m_data->m_commandProcessor->processCommand(command,m_data->m_serverStatus,&m_data->m_bulletStreamDataServerToClient[0],SHARED_MEMORY_MAX_STREAM_CHUNK_SIZE);
 	m_data->m_hasStatus = hasStatus;
-	if (hasStatus)
+	/*if (hasStatus)
 	{
 		postProcessStatus(m_data->m_serverStatus);
+		m_data->m_hasStatus = false;
 	}
+	*/
 	return hasStatus;
 }
 
@@ -777,6 +855,23 @@ int PhysicsDirect::getNumBodies() const
 	return m_data->m_bodyJointMap.size();
 }
 
+int PhysicsDirect::getNumUserConstraints() const
+{
+    return m_data->m_userConstraintInfoMap.size();
+}
+
+int PhysicsDirect::getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint&info) const
+{
+    b3UserConstraint* constraintPtr =m_data->m_userConstraintInfoMap[constraintUniqueId];
+    if (constraintPtr)
+    {
+        info = *constraintPtr;
+        return 1;
+    }
+    return 0;
+}
+
+
 
 int PhysicsDirect::getBodyUniqueId(int serialIndex) const
 {
diff --git a/examples/SharedMemory/PhysicsDirect.h b/examples/SharedMemory/PhysicsDirect.h
index bdaced974..a8b4c6aac 100644
--- a/examples/SharedMemory/PhysicsDirect.h
+++ b/examples/SharedMemory/PhysicsDirect.h
@@ -63,6 +63,10 @@ public:
 
     virtual bool getJointInfo(int bodyIndex, int jointIndex, struct b3JointInfo& info) const;
 
+    virtual int getNumUserConstraints() const;
+    
+    virtual int getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint& info) const;
+    
 	///todo: move this out of the
     virtual void setSharedMemoryKey(int key);
 
@@ -86,7 +90,7 @@ public:
 
 	virtual void getCachedRaycastHits(struct b3RaycastInformation* raycastHits);
 
-	//those 2 APIs are for internal use for visualization
+	//the following APIs are for internal use for visualization:
 	virtual bool connect(struct GUIHelperInterface* guiHelper);
 	virtual void renderScene();
 	virtual void debugDraw(int debugDrawMode);
diff --git a/examples/SharedMemory/PhysicsLoopBack.cpp b/examples/SharedMemory/PhysicsLoopBack.cpp
index 626653f43..6de63e374 100644
--- a/examples/SharedMemory/PhysicsLoopBack.cpp
+++ b/examples/SharedMemory/PhysicsLoopBack.cpp
@@ -99,7 +99,16 @@ bool PhysicsLoopBack::getJointInfo(int bodyIndex, int jointIndex, struct b3Joint
 	return m_data->m_physicsClient->getJointInfo(bodyIndex,jointIndex,info);
 }
 
-///todo: move this out of the
+int PhysicsLoopBack::getNumUserConstraints() const
+{
+    return m_data->m_physicsClient->getNumUserConstraints();
+}
+int PhysicsLoopBack::getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint&info) const
+{
+    return m_data->m_physicsClient->getUserConstraintInfo( constraintUniqueId, info);
+}
+
+///todo: move this out of the interface
 void PhysicsLoopBack::setSharedMemoryKey(int key)
 {
 	m_data->m_physicsServer->setSharedMemoryKey(key);
diff --git a/examples/SharedMemory/PhysicsLoopBack.h b/examples/SharedMemory/PhysicsLoopBack.h
index 0eaea6ff8..3cbeba296 100644
--- a/examples/SharedMemory/PhysicsLoopBack.h
+++ b/examples/SharedMemory/PhysicsLoopBack.h
@@ -48,6 +48,10 @@ public:
 
     virtual bool getJointInfo(int bodyIndex, int jointIndex, struct b3JointInfo& info) const;
 
+    virtual int getNumUserConstraints() const;
+    
+    virtual int getUserConstraintInfo(int constraintUniqueId, struct b3UserConstraint&info) const;
+    
 	///todo: move this out of the
     virtual void setSharedMemoryKey(int key);
 
diff --git a/examples/SharedMemory/PhysicsServerCommandProcessor.cpp b/examples/SharedMemory/PhysicsServerCommandProcessor.cpp
index af2d5c2d8..5d000f6dc 100644
--- a/examples/SharedMemory/PhysicsServerCommandProcessor.cpp
+++ b/examples/SharedMemory/PhysicsServerCommandProcessor.cpp
@@ -135,6 +135,9 @@ struct InteralUserConstraintData
 {
 	btTypedConstraint* m_rbConstraint;
 	btMultiBodyConstraint* m_mbConstraint;
+
+	b3UserConstraint m_userConstraintData;
+
 	InteralUserConstraintData()
 		:m_rbConstraint(0),
 		m_mbConstraint(0)
@@ -834,6 +837,9 @@ void PhysicsServerCommandProcessor::deleteDynamicsWorld()
 	deleteCachedInverseDynamicsBodies();
 	deleteCachedInverseKinematicsBodies();
 
+	m_data->m_userConstraints.clear();
+	m_data->m_saveWorldBodyData.clear();
+
 	for (int i=0;i<m_data->m_multiBodyJointFeedbacks.size();i++)
 	{
 		delete m_data->m_multiBodyJointFeedbacks[i];
@@ -1760,6 +1766,17 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 						}
 					}
 					serverStatusOut.m_sdfLoadedArgs.m_numBodies = actualNumBodies;
+
+					int usz = m_data->m_userConstraints.size();
+					serverStatusOut.m_sdfLoadedArgs.m_numUserConstraints = usz;
+					for (int i=0;i<usz;i++)
+					{
+
+						int key = m_data->m_userConstraints.getKeyAtIndex(i).getUid1();
+						int uid = m_data->m_userConstraints.getAtIndex(i)->m_userConstraintData.m_userConstraintUniqueId;
+						serverStatusOut.m_sdfLoadedArgs.m_userConstraintUniqueIds[i] = key;
+					}
+
 					serverStatusOut.m_type = CMD_SYNC_BODY_INFO_COMPLETED;
 					hasStatus = true;
 					break;
@@ -1785,7 +1802,7 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 					
 					{
 						//saveWorld(clientCmd.m_sdfArguments.m_sdfFileName);
-
+						int constraintCount = 0;
 						FILE* f = fopen(clientCmd.m_sdfArguments.m_sdfFileName,"w");
 						if (f)
 						{
@@ -1900,6 +1917,93 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 								};
 							}
 
+							//user constraints
+							{
+								for (int i=0;i<m_data->m_userConstraints.size();i++)
+								{
+									InteralUserConstraintData* ucptr = m_data->m_userConstraints.getAtIndex(i);
+									b3UserConstraint& uc = ucptr->m_userConstraintData;
+
+									int parentBodyIndex=uc.m_parentBodyIndex;
+									int parentJointIndex=uc.m_parentJointIndex;
+									int childBodyIndex=uc.m_childBodyIndex;
+									int childJointIndex=uc.m_childJointIndex;
+									btVector3 jointAxis(uc.m_jointAxis[0],uc.m_jointAxis[1],uc.m_jointAxis[2]);
+									btVector3 pivotParent(uc.m_parentFrame[0],uc.m_parentFrame[1],uc.m_parentFrame[2]);
+									btVector3 pivotChild(uc.m_childFrame[0],uc.m_childFrame[1],uc.m_childFrame[2]);
+									btQuaternion ornFrameParent(uc.m_parentFrame[3],uc.m_parentFrame[4],uc.m_parentFrame[5],uc.m_parentFrame[6]);
+									btQuaternion ornFrameChild(uc.m_childFrame[3],uc.m_childFrame[4],uc.m_childFrame[5],uc.m_childFrame[6]);
+									{
+										char jointTypeStr[1024]="FIXED";
+										bool hasKnownJointType = true;
+
+										switch (uc.m_jointType)
+										{
+											case eRevoluteType:
+											{
+												sprintf(jointTypeStr,"p.JOINT_REVOLUTE");
+												break;
+											}
+											case ePrismaticType:
+											{
+												sprintf(jointTypeStr,"p.JOINT_PRISMATIC");
+												break;
+											}
+											case eSphericalType:
+											{
+												sprintf(jointTypeStr,"p.JOINT_SPHERICAL");
+												break;
+											}
+											case ePlanarType:
+											{
+												sprintf(jointTypeStr,"p.JOINT_PLANAR");
+												break;
+											}
+											case eFixedType :
+											{
+												sprintf(jointTypeStr,"p.JOINT_FIXED");
+												break;
+											}
+											case ePoint2PointType:
+											{
+												sprintf(jointTypeStr,"p.JOINT_POINT2POINT");
+												break;											}
+											default:
+											{
+												hasKnownJointType = false;
+												b3Warning("unknown constraint type in SAVE_WORLD");
+											}
+										};
+										if (hasKnownJointType)
+										{
+											{
+												sprintf(line,"cid%d = p.createConstraint(%d,%d,%d,%d,%s,[%f,%f,%f],[%f,%f,%f],[%f,%f,%f],[%f,%f,%f,%f],[%f,%f,%f,%f])\n",
+													constraintCount,
+													parentBodyIndex,
+													parentJointIndex,
+													childBodyIndex,
+													childJointIndex,
+													jointTypeStr,
+													jointAxis[0],jointAxis[1],jointAxis[2],
+													pivotParent[0],pivotParent[1],pivotParent[2],
+													pivotChild[0],pivotChild[1],pivotChild[2],
+													ornFrameParent[0],ornFrameParent[1],ornFrameParent[2],ornFrameParent[3],
+													ornFrameChild[0],ornFrameChild[1],ornFrameChild[2],ornFrameChild[3]
+													);
+												int len = strlen(line);
+												fwrite(line,len,1,f);
+											}
+											{
+												sprintf(line,"p.changeConstraint(cid%d,maxForce=%f)\n",constraintCount,uc.m_maxAppliedForce);
+												int len = strlen(line);
+												fwrite(line,len,1,f);
+												constraintCount++;
+											}
+										}
+									}
+								}
+							}
+
 							{
 								btVector3 grav=this->m_data->m_dynamicsWorld->getGravity();
 								sprintf(line,"p.setGravity(%f,%f,%f)\n",grav[0],grav[1],grav[2]);
@@ -1942,6 +2046,7 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 
                             //serverStatusOut.m_type = CMD_SDF_LOADING_FAILED;
                             serverStatusOut.m_sdfLoadedArgs.m_numBodies = m_data->m_sdfRecentLoadedBodies.size();
+							serverStatusOut.m_sdfLoadedArgs.m_numUserConstraints = 0;
                             int maxBodies = btMin(MAX_SDF_BODIES, serverStatusOut.m_sdfLoadedArgs.m_numBodies);
                             for (int i=0;i<maxBodies;i++)
                             {
@@ -3545,126 +3650,159 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 					SharedMemoryStatus& serverCmd =serverStatusOut;
                     serverCmd.m_type = CMD_USER_CONSTRAINT_FAILED;
                     hasStatus = true;
-
+					if (clientCmd.m_updateFlags & USER_CONSTRAINT_REQUEST_INFO)
+					{
+						int userConstraintUidChange = clientCmd.m_userConstraintArguments.m_userConstraintUniqueId;
+						InteralUserConstraintData* userConstraintPtr = m_data->m_userConstraints.find(userConstraintUidChange);
+						if (userConstraintPtr)
+						{
+							serverCmd.m_userConstraintResultArgs = userConstraintPtr->m_userConstraintData;
+							serverCmd.m_type = CMD_USER_CONSTRAINT_INFO_COMPLETED;
+						}
+					}
 					if (clientCmd.m_updateFlags & USER_CONSTRAINT_ADD_CONSTRAINT)
 					{
+						btScalar defaultMaxForce = 500.0;
 						InteralBodyData* parentBody = m_data->getHandle(clientCmd.m_userConstraintArguments.m_parentBodyIndex);
 						if (parentBody && parentBody->m_multiBody)
 						{
-							InteralBodyData* childBody = clientCmd.m_userConstraintArguments.m_childBodyIndex>=0 ? m_data->getHandle(clientCmd.m_userConstraintArguments.m_childBodyIndex):0;
-							//also create a constraint with just a single multibody/rigid body without child
-							//if (childBody)
+							if ((clientCmd.m_userConstraintArguments.m_parentJointIndex>=-1) && clientCmd.m_userConstraintArguments.m_parentJointIndex < parentBody->m_multiBody->getNumLinks())
 							{
-								btVector3 pivotInParent(clientCmd.m_userConstraintArguments.m_parentFrame[0], clientCmd.m_userConstraintArguments.m_parentFrame[1], clientCmd.m_userConstraintArguments.m_parentFrame[2]);
-								btVector3 pivotInChild(clientCmd.m_userConstraintArguments.m_childFrame[0], clientCmd.m_userConstraintArguments.m_childFrame[1], clientCmd.m_userConstraintArguments.m_childFrame[2]);
-								btMatrix3x3 frameInParent(btQuaternion(clientCmd.m_userConstraintArguments.m_parentFrame[3], clientCmd.m_userConstraintArguments.m_parentFrame[4], clientCmd.m_userConstraintArguments.m_parentFrame[5], clientCmd.m_userConstraintArguments.m_parentFrame[6]));
-								btMatrix3x3 frameInChild(btQuaternion(clientCmd.m_userConstraintArguments.m_childFrame[3], clientCmd.m_userConstraintArguments.m_childFrame[4], clientCmd.m_userConstraintArguments.m_childFrame[5], clientCmd.m_userConstraintArguments.m_childFrame[6]));
-								btVector3 jointAxis(clientCmd.m_userConstraintArguments.m_jointAxis[0], clientCmd.m_userConstraintArguments.m_jointAxis[1], clientCmd.m_userConstraintArguments.m_jointAxis[2]);
-								if (clientCmd.m_userConstraintArguments.m_jointType == eFixedType)
+								InteralBodyData* childBody = clientCmd.m_userConstraintArguments.m_childBodyIndex>=0 ? m_data->getHandle(clientCmd.m_userConstraintArguments.m_childBodyIndex):0;
+								//also create a constraint with just a single multibody/rigid body without child
+								//if (childBody)
 								{
-									if (childBody && childBody->m_multiBody)
+									btVector3 pivotInParent(clientCmd.m_userConstraintArguments.m_parentFrame[0], clientCmd.m_userConstraintArguments.m_parentFrame[1], clientCmd.m_userConstraintArguments.m_parentFrame[2]);
+									btVector3 pivotInChild(clientCmd.m_userConstraintArguments.m_childFrame[0], clientCmd.m_userConstraintArguments.m_childFrame[1], clientCmd.m_userConstraintArguments.m_childFrame[2]);
+									btMatrix3x3 frameInParent(btQuaternion(clientCmd.m_userConstraintArguments.m_parentFrame[3], clientCmd.m_userConstraintArguments.m_parentFrame[4], clientCmd.m_userConstraintArguments.m_parentFrame[5], clientCmd.m_userConstraintArguments.m_parentFrame[6]));
+									btMatrix3x3 frameInChild(btQuaternion(clientCmd.m_userConstraintArguments.m_childFrame[3], clientCmd.m_userConstraintArguments.m_childFrame[4], clientCmd.m_userConstraintArguments.m_childFrame[5], clientCmd.m_userConstraintArguments.m_childFrame[6]));
+									btVector3 jointAxis(clientCmd.m_userConstraintArguments.m_jointAxis[0], clientCmd.m_userConstraintArguments.m_jointAxis[1], clientCmd.m_userConstraintArguments.m_jointAxis[2]);
+									if (clientCmd.m_userConstraintArguments.m_jointType == eFixedType)
 									{
-										btMultiBodyFixedConstraint* multibodyFixed = new btMultiBodyFixedConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild,frameInParent,frameInChild);
-										multibodyFixed->setMaxAppliedImpulse(500.0);
-										m_data->m_dynamicsWorld->addMultiBodyConstraint(multibodyFixed);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = multibodyFixed;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+										if (childBody && childBody->m_multiBody)
+										{
+											if ((clientCmd.m_userConstraintArguments.m_childJointIndex>=-1) && (clientCmd.m_userConstraintArguments.m_childJointIndex <childBody->m_multiBody->getNumLinks()))
+											{
+												btMultiBodyFixedConstraint* multibodyFixed = new btMultiBodyFixedConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild,frameInParent,frameInChild);
+												multibodyFixed->setMaxAppliedImpulse(defaultMaxForce);
+												m_data->m_dynamicsWorld->addMultiBodyConstraint(multibodyFixed);
+												InteralUserConstraintData userConstraintData;
+												userConstraintData.m_mbConstraint = multibodyFixed;
+												int uid = m_data->m_userConstraintUIDGenerator++;
+												serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+												serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+												userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+												m_data->m_userConstraints.insert(uid,userConstraintData);
+												serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+											}
 									
-									}
-									else
-									{
-										btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
-										btMultiBodyFixedConstraint* rigidbodyFixed = new btMultiBodyFixedConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild,frameInParent,frameInChild);
-										rigidbodyFixed->setMaxAppliedImpulse(500.0);
-										btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
-										world->addMultiBodyConstraint(rigidbodyFixed);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = rigidbodyFixed;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
-									}
+										}
+										else
+										{
+											btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
+											btMultiBodyFixedConstraint* rigidbodyFixed = new btMultiBodyFixedConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild,frameInParent,frameInChild);
+											rigidbodyFixed->setMaxAppliedImpulse(defaultMaxForce);
+											btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
+											world->addMultiBodyConstraint(rigidbodyFixed);
+											InteralUserConstraintData userConstraintData;
+											userConstraintData.m_mbConstraint = rigidbodyFixed;
+											int uid = m_data->m_userConstraintUIDGenerator++;
+											serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+											serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+											serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+											userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+											m_data->m_userConstraints.insert(uid,userConstraintData);
+											serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+										}
 								
-								}
-								else if (clientCmd.m_userConstraintArguments.m_jointType == ePrismaticType)
-								{
-									if (childBody &&  childBody->m_multiBody)
-									{
-										btMultiBodySliderConstraint* multibodySlider = new btMultiBodySliderConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild,frameInParent,frameInChild,jointAxis);
-										multibodySlider->setMaxAppliedImpulse(500.0);
-										m_data->m_dynamicsWorld->addMultiBodyConstraint(multibodySlider);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = multibodySlider;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
 									}
-									else
+									else if (clientCmd.m_userConstraintArguments.m_jointType == ePrismaticType)
 									{
-										btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
+										if (childBody &&  childBody->m_multiBody)
+										{
+											btMultiBodySliderConstraint* multibodySlider = new btMultiBodySliderConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild,frameInParent,frameInChild,jointAxis);
+											multibodySlider->setMaxAppliedImpulse(defaultMaxForce);
+											m_data->m_dynamicsWorld->addMultiBodyConstraint(multibodySlider);
+											InteralUserConstraintData userConstraintData;
+											userConstraintData.m_mbConstraint = multibodySlider;
+											int uid = m_data->m_userConstraintUIDGenerator++;
+											serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+											serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+											serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+											userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+											m_data->m_userConstraints.insert(uid,userConstraintData);
+											serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+										}
+										else
+										{
+											btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
 									
-										btMultiBodySliderConstraint* rigidbodySlider = new btMultiBodySliderConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild,frameInParent,frameInChild,jointAxis);
-										rigidbodySlider->setMaxAppliedImpulse(500.0);
-										btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
-										world->addMultiBodyConstraint(rigidbodySlider);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = rigidbodySlider;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
-									}
+											btMultiBodySliderConstraint* rigidbodySlider = new btMultiBodySliderConstraint(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild,frameInParent,frameInChild,jointAxis);
+											rigidbodySlider->setMaxAppliedImpulse(defaultMaxForce);
+											btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
+											world->addMultiBodyConstraint(rigidbodySlider);
+											InteralUserConstraintData userConstraintData;
+											userConstraintData.m_mbConstraint = rigidbodySlider;
+											int uid = m_data->m_userConstraintUIDGenerator++;
+											serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+											serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+											serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+											userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+											m_data->m_userConstraints.insert(uid,userConstraintData);
+											serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;										}
 								
-								} else if (clientCmd.m_userConstraintArguments.m_jointType == ePoint2PointType)
-								{
-									if (childBody && childBody->m_multiBody)
+									} else if (clientCmd.m_userConstraintArguments.m_jointType == ePoint2PointType)
 									{
-										btMultiBodyPoint2Point* p2p = new btMultiBodyPoint2Point(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild);
-										p2p->setMaxAppliedImpulse(500);
-										m_data->m_dynamicsWorld->addMultiBodyConstraint(p2p);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = p2p;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
-									}
-									else
-									{
-										btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
+										if (childBody && childBody->m_multiBody)
+										{
+											btMultiBodyPoint2Point* p2p = new btMultiBodyPoint2Point(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,childBody->m_multiBody,clientCmd.m_userConstraintArguments.m_childJointIndex,pivotInParent,pivotInChild);
+											p2p->setMaxAppliedImpulse(defaultMaxForce);
+											m_data->m_dynamicsWorld->addMultiBodyConstraint(p2p);
+											InteralUserConstraintData userConstraintData;
+											userConstraintData.m_mbConstraint = p2p;
+											int uid = m_data->m_userConstraintUIDGenerator++;
+											serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+											serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+											serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+											userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+											m_data->m_userConstraints.insert(uid,userConstraintData);
+											serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+										}
+										else
+										{
+											btRigidBody* rb = childBody? childBody->m_rigidBody : 0;
 									
-										btMultiBodyPoint2Point* p2p = new btMultiBodyPoint2Point(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild);
-										p2p->setMaxAppliedImpulse(500);
-										btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
-										world->addMultiBodyConstraint(p2p);
-										InteralUserConstraintData userConstraintData;
-										userConstraintData.m_mbConstraint = p2p;
-										int uid = m_data->m_userConstraintUIDGenerator++;
-										m_data->m_userConstraints.insert(uid,userConstraintData);
-										serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
-										serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
-									}
+											btMultiBodyPoint2Point* p2p = new btMultiBodyPoint2Point(parentBody->m_multiBody,clientCmd.m_userConstraintArguments.m_parentJointIndex,rb,pivotInParent,pivotInChild);
+											p2p->setMaxAppliedImpulse(defaultMaxForce);
+											btMultiBodyDynamicsWorld* world = (btMultiBodyDynamicsWorld*) m_data->m_dynamicsWorld;
+											world->addMultiBodyConstraint(p2p);
+											InteralUserConstraintData userConstraintData;
+											userConstraintData.m_mbConstraint = p2p;
+											int uid = m_data->m_userConstraintUIDGenerator++;
+											serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+											serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = uid;
+											serverCmd.m_userConstraintResultArgs.m_maxAppliedForce = defaultMaxForce;
+											userConstraintData.m_userConstraintData = serverCmd.m_userConstraintResultArgs;
+											m_data->m_userConstraints.insert(uid,userConstraintData);
+											serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+										}
 								
-								} else
-								{
-									b3Warning("unknown constraint type");
-								}
+									} else
+									{
+										b3Warning("unknown constraint type");
+									}
 
 							
+								}
+							}
 							}
-						}
 					}
 
 					if (clientCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_CONSTRAINT)
 					{
-						int userConstraintUidRemove = clientCmd.m_userConstraintArguments.m_userConstraintUniqueId;
-						InteralUserConstraintData* userConstraintPtr = m_data->m_userConstraints.find(userConstraintUidRemove);
+						serverCmd.m_type = CMD_CHANGE_USER_CONSTRAINT_FAILED;
+						int userConstraintUidChange = clientCmd.m_userConstraintArguments.m_userConstraintUniqueId;
+						InteralUserConstraintData* userConstraintPtr = m_data->m_userConstraints.find(userConstraintUidChange);
 						if (userConstraintPtr)
 						{
 							if (userConstraintPtr->m_mbConstraint)
@@ -3674,7 +3812,9 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 									btVector3 pivotInB(clientCmd.m_userConstraintArguments.m_childFrame[0],
 										clientCmd.m_userConstraintArguments.m_childFrame[1],
 										clientCmd.m_userConstraintArguments.m_childFrame[2]);
-
+									userConstraintPtr->m_userConstraintData.m_childFrame[0] = clientCmd.m_userConstraintArguments.m_childFrame[0];
+									userConstraintPtr->m_userConstraintData.m_childFrame[1] = clientCmd.m_userConstraintArguments.m_childFrame[1];
+									userConstraintPtr->m_userConstraintData.m_childFrame[2] = clientCmd.m_userConstraintArguments.m_childFrame[2];
 									userConstraintPtr->m_mbConstraint->setPivotInB(pivotInB);
 								}
 								if (clientCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_FRAME_ORN_IN_B)
@@ -3683,13 +3823,17 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 										clientCmd.m_userConstraintArguments.m_childFrame[4],
 										clientCmd.m_userConstraintArguments.m_childFrame[5],
 										clientCmd.m_userConstraintArguments.m_childFrame[6]);
-
+									userConstraintPtr->m_userConstraintData.m_childFrame[3] = clientCmd.m_userConstraintArguments.m_childFrame[3];
+									userConstraintPtr->m_userConstraintData.m_childFrame[4] = clientCmd.m_userConstraintArguments.m_childFrame[4];
+									userConstraintPtr->m_userConstraintData.m_childFrame[5] = clientCmd.m_userConstraintArguments.m_childFrame[5];
+									userConstraintPtr->m_userConstraintData.m_childFrame[6] = clientCmd.m_userConstraintArguments.m_childFrame[6];
 									btMatrix3x3 childFrameBasis(childFrameOrn);
 									userConstraintPtr->m_mbConstraint->setFrameInB(childFrameBasis);
 								}
 								if (clientCmd.m_updateFlags & USER_CONSTRAINT_CHANGE_MAX_FORCE)
 								{
 									btScalar maxImp = clientCmd.m_userConstraintArguments.m_maxAppliedForce*m_data->m_physicsDeltaTime;
+									userConstraintPtr->m_userConstraintData.m_maxAppliedForce = clientCmd.m_userConstraintArguments.m_maxAppliedForce;
 									userConstraintPtr->m_mbConstraint->setMaxAppliedImpulse(maxImp);
 								}
 							}
@@ -3697,12 +3841,15 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 							{
 								//todo
 							}
-							serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = -1;
-							serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+							serverCmd.m_userConstraintResultArgs = clientCmd.m_userConstraintArguments;
+							serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = userConstraintUidChange;
+							serverCmd.m_updateFlags = clientCmd.m_updateFlags;
+							serverCmd.m_type = CMD_CHANGE_USER_CONSTRAINT_COMPLETED;
 						}
 					}
 					if (clientCmd.m_updateFlags & USER_CONSTRAINT_REMOVE_CONSTRAINT)
 					{
+						serverCmd.m_type = CMD_REMOVE_USER_CONSTRAINT_FAILED;
 						int userConstraintUidRemove = clientCmd.m_userConstraintArguments.m_userConstraintUniqueId;
 						InteralUserConstraintData* userConstraintPtr = m_data->m_userConstraints.find(userConstraintUidRemove);
 						if (userConstraintPtr)
@@ -3717,8 +3864,10 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 							{
 
 							}
-							serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = -1;
-							serverCmd.m_type = CMD_USER_CONSTRAINT_COMPLETED;
+							serverCmd.m_userConstraintResultArgs.m_userConstraintUniqueId = userConstraintUidRemove;
+							serverCmd.m_type = CMD_REMOVE_USER_CONSTRAINT_COMPLETED;
+
+                            
 						}
 
 						
@@ -3974,7 +4123,8 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 							
 							int numRb = importer->getNumRigidBodies();
 							serverStatusOut.m_sdfLoadedArgs.m_numBodies = 0;
-
+							serverStatusOut.m_sdfLoadedArgs.m_numUserConstraints = 0;
+                            
 							for( int i=0;i<numRb;i++)
 							{
 								btCollisionObject* colObj = importer->getRigidBodyByIndex(i);
@@ -4044,6 +4194,7 @@ bool PhysicsServerCommandProcessor::processCommand(const struct SharedMemoryComm
 							m_data->m_guiHelper->autogenerateGraphicsObjects(this->m_data->m_dynamicsWorld);
 
                             serverStatusOut.m_sdfLoadedArgs.m_numBodies = m_data->m_sdfRecentLoadedBodies.size();
+							serverStatusOut.m_sdfLoadedArgs.m_numUserConstraints = 0;
                             int maxBodies = btMin(MAX_SDF_BODIES, serverStatusOut.m_sdfLoadedArgs.m_numBodies);
                             for (int i=0;i<maxBodies;i++)
                             {
@@ -4539,7 +4690,8 @@ void PhysicsServerCommandProcessor::resetSimulation()
 	m_data->m_gripperRigidbodyFixed = 0;
 
 }
-//todo: move this to Python/scripting
+
+//todo: move this to Python/scripting (it is almost ready to be removed!)
 void PhysicsServerCommandProcessor::createDefaultRobotAssets()
 {
 	static btAlignedObjectArray<char> gBufferServerToClient;
diff --git a/examples/SharedMemory/SharedMemoryCommands.h b/examples/SharedMemory/SharedMemoryCommands.h
index 1c85c3b7d..1f599c685 100644
--- a/examples/SharedMemory/SharedMemoryCommands.h
+++ b/examples/SharedMemory/SharedMemoryCommands.h
@@ -432,6 +432,8 @@ struct SdfLoadedArgs
 {
     int m_numBodies;
     int m_bodyUniqueIds[MAX_SDF_BODIES];
+    int m_numUserConstraints;
+	int m_userConstraintUniqueIds[MAX_SDF_BODIES];
     
     ///@todo(erwincoumans) load cameras, lights etc
     //int m_numCameras; 
@@ -541,27 +543,13 @@ enum EnumUserConstraintFlags
 	USER_CONSTRAINT_CHANGE_PIVOT_IN_B=8,
 	USER_CONSTRAINT_CHANGE_FRAME_ORN_IN_B=16,
 	USER_CONSTRAINT_CHANGE_MAX_FORCE=32,
+	USER_CONSTRAINT_REQUEST_INFO=64,
 	
 };
 
-struct UserConstraintArgs
-{
-    int m_parentBodyIndex;
-    int m_parentJointIndex;
-    int m_childBodyIndex;
-    int m_childJointIndex;
-    double m_parentFrame[7];
-    double m_childFrame[7];
-    double m_jointAxis[3];
-    int m_jointType;
-	double m_maxAppliedForce;
-	int m_userConstraintUniqueId;
-};
 
-struct UserConstraintResultArgs
-{
-	int m_userConstraintUniqueId;
-};
+
+
 
 enum EnumUserDebugDrawFlags
 {
@@ -659,7 +647,7 @@ struct SharedMemoryCommand
         struct ExternalForceArgs m_externalForceArguments;
 		struct CalculateInverseDynamicsArgs m_calculateInverseDynamicsArguments;
         struct CalculateJacobianArgs m_calculateJacobianArguments;
-        struct UserConstraintArgs m_userConstraintArguments;
+        struct b3UserConstraint m_userConstraintArguments;
         struct RequestContactDataArgs m_requestContactPointArguments;
 		struct RequestOverlappingObjectsArgs m_requestOverlappingObjectsArgs;
         struct RequestVisualShapeDataArgs m_requestVisualShapeDataArguments;
@@ -708,6 +696,10 @@ struct SharedMemoryStatus
 	int		m_numDataStreamBytes;
 	char*	m_dataStream;
 
+	//m_updateFlags is a bit fields to tell which parameters were updated, 
+	//m_updateFlags is ignored for most status messages
+    int m_updateFlags;
+
 	union
 	{
 		struct BulletDataStreamArgs	m_dataStreamArguments;
@@ -723,7 +715,7 @@ struct SharedMemoryStatus
 		struct CalculateInverseKinematicsResultArgs m_inverseKinematicsResultArgs;
 		struct SendVisualShapeDataArgs m_sendVisualShapeArgs;
 		struct UserDebugDrawResultArgs m_userDebugDrawArgs;
-		struct UserConstraintResultArgs m_userConstraintResultArgs;
+		struct b3UserConstraint m_userConstraintResultArgs;
 		struct SendVREvents m_sendVREvents;
 		struct SendRaycastHits m_raycastHits;
 	};
diff --git a/examples/SharedMemory/SharedMemoryPublic.h b/examples/SharedMemory/SharedMemoryPublic.h
index e8350560a..071d371eb 100644
--- a/examples/SharedMemory/SharedMemoryPublic.h
+++ b/examples/SharedMemory/SharedMemoryPublic.h
@@ -112,6 +112,11 @@ enum EnumSharedMemoryServerStatus
 		CMD_USER_DEBUG_DRAW_PARAMETER_COMPLETED,
 		CMD_USER_DEBUG_DRAW_FAILED,
 		CMD_USER_CONSTRAINT_COMPLETED,
+		CMD_USER_CONSTRAINT_INFO_COMPLETED,
+        CMD_REMOVE_USER_CONSTRAINT_COMPLETED,
+        CMD_CHANGE_USER_CONSTRAINT_COMPLETED,
+		CMD_REMOVE_USER_CONSTRAINT_FAILED,
+        CMD_CHANGE_USER_CONSTRAINT_FAILED,
 		CMD_USER_CONSTRAINT_FAILED,
 		CMD_REQUEST_VR_EVENTS_DATA_COMPLETED,
 		CMD_REQUEST_RAY_CAST_INTERSECTIONS_COMPLETED,
@@ -164,6 +169,20 @@ struct b3JointInfo
     double m_jointAxis[3]; // joint axis in parent local frame
 };
 
+struct b3UserConstraint
+{
+    int m_parentBodyIndex;
+    int m_parentJointIndex;
+    int m_childBodyIndex;
+    int m_childJointIndex;
+    double m_parentFrame[7];
+    double m_childFrame[7];
+    double m_jointAxis[3];
+    int m_jointType;
+    double m_maxAppliedForce;
+    int m_userConstraintUniqueId;
+};
+
 struct b3BodyInfo
 {
 	const char* m_baseName;
diff --git a/examples/pybullet/pybullet.c b/examples/pybullet/pybullet.c
index e69395702..eef43f9b4 100644
--- a/examples/pybullet/pybullet.c
+++ b/examples/pybullet/pybullet.c
@@ -1578,6 +1578,7 @@ static PyObject* pybullet_getNumBodies(PyObject* self, PyObject* args, PyObject*
   }
 }
 
+
 static PyObject* pybullet_getBodyUniqueId(PyObject* self, PyObject* args, PyObject* keywds)
 {
 int physicsClientId = 0;
@@ -1650,6 +1651,122 @@ static PyObject* pybullet_getBodyInfo(PyObject* self, PyObject* args, PyObject*
 }
 
 
+static PyObject* pybullet_getConstraintInfo(PyObject* self, PyObject* args, PyObject* keywds)
+{
+    
+    {
+        int constraintUniqueId= -1;
+        b3PhysicsClientHandle sm = 0;
+        
+        int physicsClientId = 0;
+        static char *kwlist[] = { "constraintUniqueId", "physicsClientId", NULL };
+        if (!PyArg_ParseTupleAndKeywords(args, keywds, "i|i", kwlist,&constraintUniqueId, &physicsClientId))
+        {
+            return NULL;
+        }
+        sm = getPhysicsClient(physicsClientId);
+        if (sm == 0)
+        {
+            PyErr_SetString(SpamError, "Not connected to physics server.");
+            return NULL;
+        }
+        
+        {
+            struct b3UserConstraint constraintInfo;
+            
+            if (b3GetUserConstraintInfo(sm,constraintUniqueId, &constraintInfo))
+            {
+                PyObject* pyListConstraintInfo = PyTuple_New(11);
+
+				PyTuple_SetItem(pyListConstraintInfo,0,PyLong_FromLong(constraintInfo.m_parentBodyIndex));
+                PyTuple_SetItem(pyListConstraintInfo,1,PyLong_FromLong(constraintInfo.m_parentJointIndex));
+                PyTuple_SetItem(pyListConstraintInfo,2,PyLong_FromLong(constraintInfo.m_childBodyIndex));
+                PyTuple_SetItem(pyListConstraintInfo,3,PyLong_FromLong(constraintInfo.m_childJointIndex));
+                PyTuple_SetItem(pyListConstraintInfo,4,PyLong_FromLong(constraintInfo.m_jointType));
+                
+                {
+                    PyObject* axisObj = PyTuple_New(3);
+                    PyTuple_SetItem(axisObj,0,PyFloat_FromDouble(constraintInfo.m_jointAxis[0]));
+                    PyTuple_SetItem(axisObj,1,PyFloat_FromDouble(constraintInfo.m_jointAxis[1]));
+                    PyTuple_SetItem(axisObj,2,PyFloat_FromDouble(constraintInfo.m_jointAxis[2]));
+                    PyTuple_SetItem(pyListConstraintInfo,5,axisObj);
+                }
+                {
+                    PyObject* parentFramePositionObj = PyTuple_New(3);
+                    PyTuple_SetItem(parentFramePositionObj,0,PyFloat_FromDouble(constraintInfo.m_parentFrame[0]));
+                    PyTuple_SetItem(parentFramePositionObj,1,PyFloat_FromDouble(constraintInfo.m_parentFrame[1]));
+                    PyTuple_SetItem(parentFramePositionObj,2,PyFloat_FromDouble(constraintInfo.m_parentFrame[2]));
+                    PyTuple_SetItem(pyListConstraintInfo,6,parentFramePositionObj);
+                }
+                {
+                    PyObject* childFramePositionObj = PyTuple_New(3);
+                    PyTuple_SetItem(childFramePositionObj,0,PyFloat_FromDouble(constraintInfo.m_childFrame[0]));
+                    PyTuple_SetItem(childFramePositionObj,1,PyFloat_FromDouble(constraintInfo.m_childFrame[1]));
+                    PyTuple_SetItem(childFramePositionObj,2,PyFloat_FromDouble(constraintInfo.m_childFrame[2]));
+                    PyTuple_SetItem(pyListConstraintInfo,7,childFramePositionObj);
+                }
+				{
+                    PyObject* parentFrameOrientationObj = PyTuple_New(4);                
+					PyTuple_SetItem(parentFrameOrientationObj,0,PyFloat_FromDouble(constraintInfo.m_parentFrame[3]));
+					PyTuple_SetItem(parentFrameOrientationObj,1,PyFloat_FromDouble(constraintInfo.m_parentFrame[4]));
+					PyTuple_SetItem(parentFrameOrientationObj,2,PyFloat_FromDouble(constraintInfo.m_parentFrame[5]));
+					PyTuple_SetItem(parentFrameOrientationObj,3,PyFloat_FromDouble(constraintInfo.m_parentFrame[6]));
+                    PyTuple_SetItem(pyListConstraintInfo,8,parentFrameOrientationObj);
+				}
+								{
+                    PyObject* childFrameOrientation = PyTuple_New(4);                
+					PyTuple_SetItem(childFrameOrientation,0,PyFloat_FromDouble(constraintInfo.m_childFrame[3]));
+					PyTuple_SetItem(childFrameOrientation,1,PyFloat_FromDouble(constraintInfo.m_childFrame[4]));
+					PyTuple_SetItem(childFrameOrientation,2,PyFloat_FromDouble(constraintInfo.m_childFrame[5]));
+					PyTuple_SetItem(childFrameOrientation,3,PyFloat_FromDouble(constraintInfo.m_childFrame[6]));
+                    PyTuple_SetItem(pyListConstraintInfo,9,childFrameOrientation);
+				}
+				PyTuple_SetItem(pyListConstraintInfo,10,PyFloat_FromDouble(constraintInfo.m_maxAppliedForce));
+
+                return pyListConstraintInfo;
+            } else
+            {
+                PyErr_SetString(SpamError, "Couldn't get user constraint info");
+                return NULL;
+            }
+        }
+    }
+    
+    PyErr_SetString(SpamError, "error in getConstraintInfo.");
+    return NULL;
+}
+
+
+static PyObject* pybullet_getNumConstraints(PyObject* self, PyObject* args, PyObject* keywds)
+{
+    int numConstraints = 0;
+    int physicsClientId = 0;
+    b3PhysicsClientHandle sm = 0;
+    static char *kwlist[] = { "physicsClientId", NULL };
+    if (!PyArg_ParseTupleAndKeywords(args, keywds, "|i", kwlist, &physicsClientId))
+    {
+        return NULL;
+    }
+    sm = getPhysicsClient(physicsClientId);
+    if (sm == 0)
+    {
+        PyErr_SetString(SpamError, "Not connected to physics server.");
+        return NULL;
+    }
+    
+    numConstraints = b3GetNumUserConstraints(sm);
+    
+#if PY_MAJOR_VERSION >= 3
+    return PyLong_FromLong(numConstraints);
+#else
+    return PyInt_FromLong(numConstraints);
+#endif
+    
+
+}
+
+
+
 // Return the number of joints in an object based on
 // body index; body index is based on order of sequence
 // the object is loaded into simulation
@@ -2221,13 +2338,10 @@ static PyObject* pybullet_addUserDebugParameter(PyObject* self, PyObject* args,
   b3SharedMemoryCommandHandle commandHandle;
   b3SharedMemoryStatusHandle statusHandle;
   int statusType;
-  int res = 0;
 
   char* text;
-  double colorRGB[3]={1,1,1};
 
   
-  PyObject* textPositionObj=0;
   double rangeMin = 0.f;
   double rangeMax = 1.f;
   double startValue = 0.f;
@@ -4541,7 +4655,7 @@ static PyMethodDef SpamMethods[] = {
 	"Load multibodies from an MJCF file." },
 
 	  {"createConstraint", (PyCFunction)pybullet_createUserConstraint, METH_VARARGS | METH_KEYWORDS,
-	"Create a constraint between two bodies. Returns a (int) unique id, if successfull."
+		"Create a constraint between two bodies. Returns a (int) unique id, if successfull."
      },
 
 	{"changeConstraint", (PyCFunction)pybullet_changeUserConstraint, METH_VARARGS | METH_KEYWORDS,
@@ -4561,11 +4675,21 @@ static PyMethodDef SpamMethods[] = {
      "Get the number of bodies in the simulation."},
 
 	{"getBodyUniqueId", (PyCFunction)pybullet_getBodyUniqueId, METH_VARARGS| METH_KEYWORDS,
-     "Get the unique id of the body, given a integer serial index in range [0.. number of bodies)."},
+     "getBodyUniqueId is used after connecting to server with existing bodies."
+	 "Get the unique id of the body, given a integer range [0.. number of bodies)."},
 
 	{"getBodyInfo",(PyCFunction) pybullet_getBodyInfo, METH_VARARGS | METH_KEYWORDS,
      "Get the body info, given a body unique id."},
 	
+    {"getNumConstraints", (PyCFunction)pybullet_getNumConstraints, METH_VARARGS| METH_KEYWORDS,
+        "Get the number of user-created constraints in the simulation."},
+
+    {"getConstraintInfo",(PyCFunction) pybullet_getConstraintInfo, METH_VARARGS | METH_KEYWORDS,
+     "Get the user-created constraint info, given a constraint unique id."},
+    
+	{"getConstraintUniqueId", (PyCFunction)pybullet_getBodyUniqueId, METH_VARARGS| METH_KEYWORDS,
+	"Get the unique id of the constraint, given a integer index in range [0.. number of constraints)."},
+    
     {"getBasePositionAndOrientation",(PyCFunction) pybullet_getBasePositionAndOrientation,
      METH_VARARGS | METH_KEYWORDS,
      "Get the world position and orientation of the base of the object. "
diff --git a/src/BulletDynamics/Featherstone/btMultiBody.cpp b/src/BulletDynamics/Featherstone/btMultiBody.cpp
index eb68b0288..dd5f253b6 100644
--- a/src/BulletDynamics/Featherstone/btMultiBody.cpp
+++ b/src/BulletDynamics/Featherstone/btMultiBody.cpp
@@ -430,6 +430,13 @@ const btQuaternion & btMultiBody::getParentToLocalRot(int i) const
 
 btVector3 btMultiBody::localPosToWorld(int i, const btVector3 &local_pos) const
 {
+	btAssert(i>=-1);
+	btAssert(i<m_links.size());
+	if ((i<-1) || (i>=m_links.size()))
+	{
+		return btVector3(SIMD_INFINITY,SIMD_INFINITY,SIMD_INFINITY);
+	}
+
     btVector3 result = local_pos;
     while (i != -1) {
         // 'result' is in frame i. transform it to frame parent(i)
@@ -447,6 +454,13 @@ btVector3 btMultiBody::localPosToWorld(int i, const btVector3 &local_pos) const
 
 btVector3 btMultiBody::worldPosToLocal(int i, const btVector3 &world_pos) const
 {
+	btAssert(i>=-1);
+	btAssert(i<m_links.size());
+	if ((i<-1) || (i>=m_links.size()))
+	{
+		return btVector3(SIMD_INFINITY,SIMD_INFINITY,SIMD_INFINITY);
+	}
+
     if (i == -1) {
         // world to base
         return quatRotate(getWorldToBaseRot(),(world_pos - getBasePos()));
@@ -458,6 +472,14 @@ btVector3 btMultiBody::worldPosToLocal(int i, const btVector3 &world_pos) const
 
 btVector3 btMultiBody::localDirToWorld(int i, const btVector3 &local_dir) const
 {
+	btAssert(i>=-1);
+	btAssert(i<m_links.size());
+	if ((i<-1) || (i>=m_links.size()))
+	{
+		return btVector3(SIMD_INFINITY,SIMD_INFINITY,SIMD_INFINITY);
+	}
+
+
     btVector3 result = local_dir;
     while (i != -1) {
         result = quatRotate(getParentToLocalRot(i).inverse() , result);
@@ -469,6 +491,13 @@ btVector3 btMultiBody::localDirToWorld(int i, const btVector3 &local_dir) const
 
 btVector3 btMultiBody::worldDirToLocal(int i, const btVector3 &world_dir) const
 {
+	btAssert(i>=-1);
+	btAssert(i<m_links.size());
+	if ((i<-1) || (i>=m_links.size()))
+	{
+		return btVector3(SIMD_INFINITY,SIMD_INFINITY,SIMD_INFINITY);
+	}
+
     if (i == -1) {
         return quatRotate(getWorldToBaseRot(), world_dir);
     } else {