Use quintic instead of sixtic speed, for better responsiveness and match with orbit stop behaviour

modules/autonavigation/pathsegment.cpp

@@ -142,7 +142,7 @@ void PathSegment::initCurve() {
             _start.rotation(),
             _end.rotation()
             );
-        _speedFunction = std::make_unique<SexticDampenedSpeed>();
+        _speedFunction = std::make_unique<QuinticDampenedSpeed>();
         break;
 
     case CurveType::Bezier3:
@@ -154,7 +154,7 @@ void PathSegment::initCurve() {
             _end.node()->worldPosition(),
             _curve.get()
         );
-        _speedFunction = std::make_unique<SexticDampenedSpeed>(); 
+        _speedFunction = std::make_unique<QuinticDampenedSpeed>();
         break;
 
     case CurveType::Linear:
@@ -163,7 +163,7 @@ void PathSegment::initCurve() {
             _start.rotation(), 
             _end.rotation()
         );
-        _speedFunction = std::make_unique<SexticDampenedSpeed>();
+        _speedFunction = std::make_unique<QuinticDampenedSpeed>();
         break;
 
     case CurveType::ZoomOutOverview:
@@ -175,7 +175,7 @@ void PathSegment::initCurve() {
             _end.node()->worldPosition(),
             _curve.get()
             );
-        _speedFunction = std::make_unique<SexticDampenedSpeed>();
+        _speedFunction = std::make_unique<QuinticDampenedSpeed>();
         break;
 
     default:

modules/autonavigation/speedfunction.cpp

@@ -85,4 +85,30 @@ double SexticDampenedSpeed::value(double t) const {
     return speed;
 }
 
+QuinticDampenedSpeed::QuinticDampenedSpeed() {
+    initIntegratedSum();
+}
+
+double QuinticDampenedSpeed::value(double t) const {
+    ghoul_assert(t >= 0.0 && t <= 1.0, "Variable t out of range [0,1]");
+
+    const double tPeak = 0.5;
+    double speed = 0.0;
+
+    // accelerate
+    if (t <= tPeak) {
+        double tScaled = t / tPeak;
+        speed = ghoul::cubicEaseInOut(ghoul::quadraticEaseInOut(tScaled));
+    }
+    // deaccelerate
+    else if (t <= 1.0) {
+        double tScaled = (t - tPeak) / (1.0 - tPeak);
+        speed = 1.0 - ghoul::cubicEaseInOut(ghoul::quadraticEaseInOut(tScaled));
+    }
+
+    // avoid zero speed
+    speed += 0.00001; // TODO: Minimal speed should depend on size of visible object/node
+    return speed;
+}
+
 } // namespace openspace::autonavigation

modules/autonavigation/speedfunction.h

@@ -52,6 +52,12 @@ public:
     double value(double t) const override;
 }; 
 
+class QuinticDampenedSpeed : public SpeedFunction {
+public:
+    QuinticDampenedSpeed();
+    double value(double t) const override;
+};
+
 } // namespace openspace::autonavigation
 
 #endif // __OPENSPACE_MODULE_AUTONAVIGATION___SPEEDFUNCTION___H__