Made update routine in mainLoop more robust

glfw/glow-extras/glfw/GlfwApp.cc

@@ -324,28 +324,31 @@ void GlfwApp::mainLoop()
     double lastTime = glfwGetTime();
     double lastStatsTime = lastTime;
     double timeAccum = 0.000001;
-    double renderTimestep = 1.0 / mUpdateRate;
     mCurrentTime = 0.0;
     size_t primitives = 0;
     size_t fragments = 0;
     double gpuTime = 0;
     double cpuTime = 0;
+    int updatesPerFrame = 1;
+    double renderTimestep = 1.0 / mUpdateRate; // tracks time between renders, init is for first frame only
     while (!shouldClose())
     {
         updateInput();
 
         // Update
-        auto maxTicks = mMaxFrameSkip;
-        while (timeAccum > 0)
         {
-            if (maxTicks-- < 0)
-            {
-                glow::warning() << "Too many updates queued, frame skip of " << timeAccum << " secs";
-                timeAccum = 0.0;
-                break;
-            }
+            double dt = 1.0 / mUpdateRate;
+
+            // # of updates
+            auto updates = updatesPerFrame;
+            if (timeAccum > updatesPerFrame * dt) // lags one behind: do one more
+                ++updates;
+            if (timeAccum < -dt) // is more than one ahead: skip one
+                --updates;
 
-            auto dt = 1.0 / mUpdateRate;
+            // do updates
+            for (auto i = 0; i < updates; ++i)
+            {
                 auto cpuStart = glfwGetTime();
                 update(dt);
                 cpuTime += glfwGetTime() - cpuStart;
@@ -353,6 +356,29 @@ void GlfwApp::mainLoop()
                 mCurrentTime += dt;
             }
 
+            // update adjustment (AFTER updates! timeAccum should be within -dt..dt now)
+            if (timeAccum > 2.5 * dt)
+            {
+                ++updatesPerFrame;
+                // glow::info() << "increasing frames per sec";
+            }
+            else if (timeAccum < -2.5 * dt)
+            {
+                if (updatesPerFrame > 0)
+                    --updatesPerFrame;
+                // glow::info() << "decreasing frames per sec";
+            }
+
+            // frameskip
+            if (timeAccum > mMaxFrameSkip * dt)
+            {
+                glow::warning() << "Too many updates queued, frame skip of " << timeAccum << " secs";
+                timeAccum = mMaxFrameSkip * dt * 0.5;
+            }
+
+            // glow::info() << updates << ", " << timeAccum / dt;
+        }
+
         beginRender();
 
         // Render here

glfw/glow-extras/glfw/GlfwApp.hh

@@ -79,7 +79,7 @@ class GlfwApp
 private:
     std::string mTitle = "GLFW/GLOW Application"; ///< window title
 
-    int mUpdateRate = 60;  ///< rate at which update(...) is called
+    double mUpdateRate = 60;  ///< rate at which update(...) is called
     int mMaxFrameSkip = 4; ///< maximum number of update(...) steps that are performed without rendering
 
     GLFWwindow* mWindow = nullptr; ///< current GLFW window