Let's try subtracting the long-term average from the eye directions.

interface/src/Application.cpp

@@ -1531,14 +1531,15 @@ void Application::update(float deltaTime) {
     // Set where I am looking based on my mouse ray (so that other people can see)
     glm::vec3 lookAtSpot;
 
+    //  Update faceshift
+    _faceshift.update();
+
     // if we have faceshift, use that to compute the lookat direction
     glm::vec3 lookAtRayOrigin = mouseRayOrigin, lookAtRayDirection = mouseRayDirection;
     if (_faceshift.isActive()) {
         lookAtRayOrigin = _myAvatar.getHead().calculateAverageEyePosition();
-        float averagePitch = (_faceshift.getEyeGazeLeftPitch() + _faceshift.getEyeGazeRightPitch()) / 2.0f;
+        lookAtRayDirection = _myAvatar.getHead().getOrientation() * glm::quat(glm::radians(glm::vec3(
-        float averageYaw = (_faceshift.getEyeGazeLeftYaw() + _faceshift.getEyeGazeRightYaw()) / 2.0f;
+            _faceshift.getEstimatedEyePitch(), _faceshift.getEstimatedEyeYaw(), 0.0f))) * glm::vec3(0.0f, 0.0f, -1.0f);
-        lookAtRayDirection = _myAvatar.getHead().getOrientation() *
-            glm::quat(glm::radians(glm::vec3(averagePitch, averageYaw, 0.0f))) * glm::vec3(0.0f, 0.0f, -1.0f);
     }
 
     _isLookingAtOtherAvatar = isLookingAtOtherAvatar(lookAtRayOrigin, lookAtRayDirection, lookAtSpot);
@@ -1707,8 +1708,6 @@ void Application::update(float deltaTime) {
         _serialHeadSensor.readData(deltaTime);
     }
     
-    //  Update transmitter
-    
     //  Sample hardware, update view frustum if needed, and send avatar data to mixer/nodes
     updateAvatar(deltaTime);
 

interface/src/devices/Faceshift.cpp

@@ -26,13 +26,30 @@ Faceshift::Faceshift() :
     _browHeight(0.0f),
     _browUpCenterIndex(-1),
     _mouthSize(0.0f),
-    _jawOpenIndex(-1)
+    _jawOpenIndex(-1),
+    _longTermAverageEyePitch(0.0f),
+    _longTermAverageEyeYaw(0.0f),
+    _estimatedEyePitch(0.0f),
+    _estimatedEyeYaw(0.0f)
 {
     connect(&_socket, SIGNAL(connected()), SLOT(noteConnected()));
     connect(&_socket, SIGNAL(error(QAbstractSocket::SocketError)), SLOT(noteError(QAbstractSocket::SocketError)));
     connect(&_socket, SIGNAL(readyRead()), SLOT(readFromSocket()));
 }
 
+void Faceshift::update() {
+    if (!isActive()) {
+        return;
+    }
+    float averageEyePitch = (_eyeGazeLeftPitch + _eyeGazeRightPitch) / 2.0f;
+    float averageEyeYaw = (_eyeGazeLeftYaw + _eyeGazeRightYaw) / 2.0f;
+    const float LONG_TERM_AVERAGE_SMOOTHING = 0.999f;
+    _longTermAverageEyePitch = glm::mix(averageEyePitch, _longTermAverageEyePitch, LONG_TERM_AVERAGE_SMOOTHING);
+    _longTermAverageEyeYaw = glm::mix(averageEyeYaw, _longTermAverageEyeYaw, LONG_TERM_AVERAGE_SMOOTHING);
+    _estimatedEyePitch = averageEyePitch - _longTermAverageEyePitch;
+    _estimatedEyeYaw = averageEyeYaw - _longTermAverageEyeYaw;
+}
+
 void Faceshift::reset() {
     if (isActive()) {
         string message;

interface/src/devices/Faceshift.h

@@ -35,6 +35,9 @@ public:
     float getEyeGazeRightPitch() const { return _eyeGazeRightPitch; }
     float getEyeGazeRightYaw() const { return _eyeGazeRightYaw; }
 
+    float getEstimatedEyePitch() const { return _estimatedEyePitch; }
+    float getEstimatedEyeYaw() const { return _estimatedEyeYaw; }
+
     float getLeftBlink() const { return _leftBlink; }
     float getRightBlink() const { return _rightBlink; }
 
@@ -42,6 +45,7 @@ public:
     
     float getMouthSize() const { return _mouthSize; }
 
+    void update();
     void reset();
 
 public slots:
@@ -85,6 +89,12 @@ private:
     float _mouthSize;
     
     int _jawOpenIndex;
+    
+    float _longTermAverageEyePitch;
+    float _longTermAverageEyeYaw;
+    
+    float _estimatedEyePitch;
+    float _estimatedEyeYaw;
 };
 
 #endif /* defined(__interface__Faceshift__) */