remainder->fmod!

interface/src/Application.cpp

@@ -1112,7 +1112,8 @@ void Application::paintGL() {
     // the key part (and not an exagerated part) of _lastPaintWait is accounted for.
     const float targetPeriod = getTargetFramePeriod();
     if (_lastPaintWait > EPSILON && actualPeriod > targetPeriod) {
-        deducedNonVSyncPeriod += remainder(actualPeriod, _lastPaintWait);
+        // Don't use C++ remainder(). It's authors are mathematically insane.
+        deducedNonVSyncPeriod += fmod(actualPeriod, _lastPaintWait);
     }
     _lastDeducedNonVSyncFps = 1.0f / deducedNonVSyncPeriod;
     _lastInstantaneousFps = instantaneousFps;

interface/src/avatar/AvatarManager.cpp

@@ -93,16 +93,15 @@ void AvatarManager::init() {
 
     const float target_fps = 1.0f / qApp->getTargetFramePeriod();
     _renderDistanceController.setMeasuredValueSetpoint(target_fps);
-    const float TREE_SCALE = 32768.0f; // Not in shared library, alas.
     const float SMALLEST_REASONABLE_HORIZON = 5.0f; // meters
     _renderDistanceController.setControlledValueHighLimit(1.0f / SMALLEST_REASONABLE_HORIZON);
-    _renderDistanceController.setControlledValueLowLimit(1.0f / TREE_SCALE);
+    _renderDistanceController.setControlledValueLowLimit(1.0f / (float) TREE_SCALE);
     // Advice for tuning parameters:
-    // See PIDController.h. There's a sectionon tuning in the reference.
+    // See PIDController.h. There's a section on tuning in the reference.
     // Turn on logging with the following (or from js with AvatarList.setRenderDistanceControllerHistory("avatar render", 300))
     //_renderDistanceController.setHistorySize("avatar render", target_fps * 4);
     // Note that extra logging/hysteresis is turned off in Avatar.cpp when the above logging is on.
-    _renderDistanceController.setKP(0.0005f); // Usually about 0.6 of largest that doesn't oscillate when other constants 0.
+    _renderDistanceController.setKP(0.0005f); // Usually about 0.6 of largest that doesn't oscillate when other parameters 0.
     _renderDistanceController.setKI(0.0004f); // Big enough to bring us to target with the above KP.
     _renderDistanceController.setKD(0.00001f); // A touch of kd increases the speed by which we get there.
 
@@ -136,6 +135,10 @@ void AvatarManager::updateOtherAvatars(float deltaTime) {
     
     const float fps = qApp->getLastInstanteousFps();
     const float paintWait = qApp->getLastPaintWait();
+    // The PID controller raises the controlled value when the measured value goes up.
+    // The measured value is frame rate. When the controlled value (1 / render cutoff distance)
+    // goes up, the render cutoff distance gets closer, the number of rendered avatars is less, and frame rate
+    // goes up.
     const float deduced = qApp->getLastDeducedNonVSyncFps();
     const float distance = 1.0f / _renderDistanceController.update(deduced, deltaTime, false, fps, paintWait);
     _renderDistanceAverage.updateAverage(distance);

interface/src/avatar/AvatarManager.h

@@ -102,7 +102,7 @@ private:
     QVector<AvatarManager::LocalLight> _localLights;
 
     bool _shouldShowReceiveStats = false;
-    float _renderDistance { 40.0f };
+    float _renderDistance { (float) TREE_SCALE };
     int _renderedAvatarCount {0};
     PIDController _renderDistanceController {};
     SimpleMovingAverage _renderDistanceAverage {10};

libraries/shared/src/PIDController.h

@@ -21,12 +21,12 @@
 #include <limits>
 #include <QVector>
 
-// Although our coding standard shuns abbreviations, the control systems literature pretty uniformly uses p, i, d, and dt rather than
+// Although our coding standard shuns abbreviations, the control systems literature uniformly uses p, i, d, and dt rather than
 // proportionalTerm, integralTerm, derivativeTerm, and deltaTime. Here we will be consistent with the literature.
 class PIDController {
 
 public:
-    // These four the main interface:
+    // These are the main interfaces:
     void setMeasuredValueSetpoint(float newValue) { _measuredValueSetpoint = newValue; }
     float update(float measuredValue, float dt, bool resetAccumulator = false, float FIXME1 = 0.0f, float FIXME2 = 0.0f); // returns the new computedValue
     void setHistorySize(QString label = QString(""), int size = 0) { _history.reserve(size); _history.resize(0); _label = label; } // non-empty does logging
@@ -78,9 +78,10 @@ protected:
     float _ki { 0.0f };
     float _kd { 0.0f };
 
-    // Controller state
+    // Controller operating state
     float _lastError{ 0.0f };
     float _lastAccumulation{ 0.0f };
+
     // reporting
     QVector<Row> _history{};
     QString _label{ "" };