hack for "reliable" packet send when objects stop moving

libraries/physics/src/EntityMotionState.cpp

@@ -108,7 +108,7 @@ void EntityMotionState::computeShapeInfo(ShapeInfo& info) {
     _entity->computeShapeInfo(info);
 }
 
-void EntityMotionState::sendUpdate(OctreeEditPacketSender* packetSender) {
+void EntityMotionState::sendUpdate(OctreeEditPacketSender* packetSender, uint32_t frame) {
 #ifdef USE_BULLET_PHYSICS
     if (_outgoingPacketFlags) {
         EntityItemProperties properties = _entity->getProperties();
@@ -165,12 +165,22 @@ void EntityMotionState::sendUpdate(OctreeEditPacketSender* packetSender) {
         //properties.setLastEdited(now);
 
         glm::vec3 zero(0.0f);
-        _sentMoving = (_sentVelocity == zero && _sentAngularVelocity == zero && _sentAcceleration == zero);
+        _sentMoving = !(_sentVelocity == zero && _sentAngularVelocity == zero && _sentAcceleration == zero);
+        // RELIABLE_SEND_HACK: count number of updates for entities at rest so we can stop sending them after some limit.
+        if (_sentMoving) {
+            _numNonMovingUpdates = 0;
+        } else {
+            _numNonMovingUpdates++;
+        }
 
         EntityItemID id(_entity->getID());
         EntityEditPacketSender* entityPacketSender = static_cast<EntityEditPacketSender*>(packetSender);
         entityPacketSender->queueEditEntityMessage(PacketTypeEntityAddOrEdit, id, properties);
-        _outgoingPacketFlags = 0;
+
+        // The outgoing flags only itemized WHAT to send, not WHETHER to send, hence we always set them
+        // to the full set.  These flags may be momentarily cleared by incoming external changes.  
+        _outgoingPacketFlags = DIRTY_PHYSICS_FLAGS;
+        _sentFrame = frame;
     }
 #endif // USE_BULLET_PHYSICS
 }

libraries/physics/src/EntityMotionState.h

@@ -58,7 +58,7 @@ public:
 
     void computeShapeInfo(ShapeInfo& info);
 
-    void sendUpdate(OctreeEditPacketSender* packetSender);
+    void sendUpdate(OctreeEditPacketSender* packetSender, uint32_t frame);
 
     uint32_t getIncomingDirtyFlags() const { return _entity->getDirtyFlags(); }
     void clearIncomingDirtyFlags(uint32_t flags) { _entity->clearDirtyFlags(flags); }

libraries/physics/src/ObjectMotionState.cpp

@@ -52,8 +52,8 @@ ObjectMotionState::ObjectMotionState() :
         _motionType(MOTION_TYPE_STATIC),
         _body(NULL),
         _sentMoving(false),
-        _weKnowRecipientHasReceivedNotMoving(false),
-        _outgoingPacketFlags(0),
+        _numNonMovingUpdates(0),
+        _outgoingPacketFlags(DIRTY_PHYSICS_FLAGS),
         _sentFrame(0),
         _sentPosition(0.0f),
         _sentRotation(),
@@ -109,21 +109,48 @@ void ObjectMotionState::getAngularVelocity(glm::vec3& angularVelocityOut) const
     bulletToGLM(_body->getAngularVelocity(), angularVelocityOut);
 }
 
+// RELIABLE_SEND_HACK: until we have truly reliable resends of non-moving updates
+// we alwasy resend packets for objects that have stopped moving up to some max limit.
+const int MAX_NUM_NON_MOVING_UPDATES = 5;
+
+bool ObjectMotionState::doesNotNeedToSendUpdate() const { 
+    return !_body->isActive() && _numNonMovingUpdates > MAX_NUM_NON_MOVING_UPDATES;
+}
+
 const float FIXED_SUBSTEP = 1.0f / 60.0f;
 
 bool ObjectMotionState::shouldSendUpdate(uint32_t simulationFrame, float subStepRemainder) const {
     assert(_body);
     float dt = (float)(simulationFrame - _sentFrame) * FIXED_SUBSTEP + subStepRemainder;
-    const float DEFAULT_UPDATE_PERIOD = 10.0f;
-    if (dt > DEFAULT_UPDATE_PERIOD || (_sentMoving && !_body->isActive())) {
-        return true;
+    bool isActive = _body->isActive();
+
+    if (isActive) {
+        const float MAX_UPDATE_PERIOD_FOR_ACTIVE_THINGS = 10.0f;
+        if (dt > MAX_UPDATE_PERIOD_FOR_ACTIVE_THINGS) {
+            return true;
+        }
+    } else if (_sentMoving) { 
+        if (!isActive) {
+            // this object just went inactive so send an update immediately
+            return true;
+        }
+    } else {
+        const float NON_MOVING_UPDATE_PERIOD = 1.0f;
+        if (dt > NON_MOVING_UPDATE_PERIOD && _numNonMovingUpdates < MAX_NUM_NON_MOVING_UPDATES) {
+            // RELIABLE_SEND_HACK: since we're not yet using a reliable method for non-moving update packets we repeat these
+            // at a faster rate than the MAX period above, and only send a limited number of them.
+            return true;
+        }
     }
+
     // Else we measure the error between current and extrapolated transform (according to expected behavior 
     // of remote EntitySimulation) and return true if the error is significant.
 
     // NOTE: math in done the simulation-frame, which is NOT necessarily the same as the world-frame 
     // due to _worldOffset.
 
+    // TODO: Andrew to reconcile Bullet and legacy damping coefficients.
+
     // compute position error
     glm::vec3 extrapolatedPosition = _sentPosition + dt * (_sentVelocity + (0.5f * dt) * _sentAcceleration);
 
@@ -131,7 +158,7 @@ bool ObjectMotionState::shouldSendUpdate(uint32_t simulationFrame, float subStep
     btTransform worldTrans = _body->getWorldTransform();
     bulletToGLM(worldTrans.getOrigin(), position);
     
-    float dx2 = glm::length2(position - extrapolatedPosition);
+    float dx2 = glm::distance2(position, extrapolatedPosition);
     const float MAX_POSITION_ERROR_SQUARED = 0.001f; // 0.001 m^2 ~~> 0.03 m
     if (dx2 > MAX_POSITION_ERROR_SQUARED) {
         return true;

libraries/physics/src/ObjectMotionState.h

@@ -81,9 +81,9 @@ public:
     virtual void clearIncomingDirtyFlags(uint32_t flags) = 0;
     void clearOutgoingPacketFlags(uint32_t flags) { _outgoingPacketFlags &= ~flags; }
 
-    bool doesNotNeedToSendUpdate() const { return !_body->isActive() && _weKnowRecipientHasReceivedNotMoving; }
+    bool doesNotNeedToSendUpdate() const;
     virtual bool shouldSendUpdate(uint32_t simulationFrame, float subStepRemainder) const;
-    virtual void sendUpdate(OctreeEditPacketSender* packetSender) = 0;
+    virtual void sendUpdate(OctreeEditPacketSender* packetSender, uint32_t frame) = 0;
 
     virtual MotionType computeMotionType() const = 0;
 
@@ -100,7 +100,7 @@ protected:
     btRigidBody* _body;
 
     bool _sentMoving;   // true if last update was moving
-    bool _weKnowRecipientHasReceivedNotMoving;
+    int _numNonMovingUpdates; // RELIABLE_SEND_HACK for "not so reliable" resends of packets for non-moving objects
 
     uint32_t _outgoingPacketFlags;
     uint32_t _sentFrame;

libraries/physics/src/PhysicsEngine.cpp

@@ -13,9 +13,9 @@
 // TODO DONE: make MotionState::setWorldTransform() put itself on _incomingChanges list
 // TODO DONE: give PhysicsEngine instance an _entityPacketSender
 // TODO DONE: make sure code compiles when BULLET is not found
-// TODO: make sure incoming and outgoing pipelines are connected
-// TODO: provide some sort of "reliable" send for "stopped" update
+// TODO DONE: make sure incoming and outgoing pipelines are connected
 // TODO: test entity updates (second viewer sees physics results from first)
+// TODO: provide some sort of "reliable" send for "stopped" update
 
 #include "PhysicsEngine.h"
 #ifdef USE_BULLET_PHYSICS
@@ -57,7 +57,7 @@ void PhysicsEngine::updateEntitiesInternal(const quint64& now) {
         if (state->doesNotNeedToSendUpdate()) {
             stateItr = _outgoingPackets.erase(stateItr);
         } else if (state->shouldSendUpdate(frame, subStepRemainder)) {
-            state->sendUpdate(_entityPacketSender);
+            state->sendUpdate(_entityPacketSender, frame);
             ++stateItr;
         } else {
             ++stateItr;