Improve fps counter (#1886)

vtkext/private/module/Testing/CMakeLists.txt

@@ -8,6 +8,7 @@ set(test_sources
   TestF3DOpenGLGridMapper.cxx
   TestF3DRenderPass.cxx
   TestF3DRendererWithColoring.cxx
+  TestF3DFpsCounter.cxx
   )
 
 if(F3D_MODULE_EXR)

vtkext/private/module/Testing/TestF3DFpsCounter.cxx

@@ -0,0 +1,54 @@
+#include <vtkNew.h>
+#include <vtkObjectFactory.h>
+
+#include "vtkF3DUIActor.h"
+
+#include <iostream>
+
+// subclass to retrieve internal protected values
+class vtkF3DTestUIActor : public vtkF3DUIActor
+{
+public:
+  static vtkF3DTestUIActor* New();
+  vtkTypeMacro(vtkF3DTestUIActor, vtkF3DUIActor);
+
+  size_t GetNumberOfFrameTimes() { return this->FrameTimes.size(); }
+  double GetTotalFrameTimes() { return this->TotalFrameTimes; }
+  int GetFpsValue() { return this->FpsValue; }
+};
+
+vtkObjectFactoryNewMacro(vtkF3DTestUIActor);
+
+int TestF3DFpsCounter(int argc, char* argv[])
+{
+  vtkNew<vtkF3DTestUIActor> uiActor;
+
+  // add 1000 frames at 0.01s
+  for (int i = 0; i < 1000; i++)
+  {
+    uiActor->UpdateFpsValue(0.01);
+  }
+
+  // make sure only the 100 last records are kept
+  if (uiActor->GetNumberOfFrameTimes() > 100)
+  {
+    std::cerr << "Number of frame times must be at most 100" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  // make sure only the total time kept doesn't exceed 1 second
+  if (uiActor->GetTotalFrameTimes() > 1.0)
+  {
+    std::cerr << "Number of total frame times must be at most 1.0" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  // make sure the FPS value is exactly 100
+  if (uiActor->GetFpsValue() != 100)
+  {
+    std::cerr << "Number of FPS value must be exactly 100" << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}

vtkext/private/module/vtkF3DRenderer.cxx

@@ -1552,20 +1552,26 @@ void vtkF3DRenderer::Render()
 
   auto cpuElapsed = std::chrono::high_resolution_clock::now() - cpuStart;
 
-  // Get CPU frame per seconds
-  int fps = static_cast<int>(std::round(
-    1.0 / (std::chrono::duration_cast<std::chrono::microseconds>(cpuElapsed).count() * 1e-6)));
+  vtkInformation *info = this->GetInformation();
+
+  bool uiOnly = info->Get(vtkF3DRenderPass::RENDER_UI_ONLY());
+
+  if (!uiOnly)
+  {
+   // Get CPU frame time
+   double elapsedTime = std::chrono::duration_cast<std::chrono::microseconds>(cpuElapsed).count() * 1e-6;
 
 #if !defined(__ANDROID__) && !defined(__EMSCRIPTEN__)
-  glEndQuery(GL_TIME_ELAPSED);
-  GLint elapsed;
-  glGetQueryObjectiv(this->Timer, GL_QUERY_RESULT, &elapsed);
+   glEndQuery(GL_TIME_ELAPSED);
+   GLint elapsed;
+   glGetQueryObjectiv(this->Timer, GL_QUERY_RESULT, &elapsed);
 
-  // Get min between CPU frame per seconds and GPU frame per seconds
-  fps = std::min(fps, static_cast<int>(std::round(1.0 / (elapsed * 1e-9))));
+   // Get min between CPU frame time and GPU frame time
+   elapsedTime = std::min(elapsedTime, elapsed * 1e-9);
 #endif
 
-  this->UIActor->SetFpsValue(fps);
+   this->UIActor->UpdateFpsValue(elapsedTime);
+  }
 }
 
 //----------------------------------------------------------------------------

vtkext/private/module/vtkF3DUIActor.cxx

@@ -67,9 +67,21 @@ void vtkF3DUIActor::SetFpsCounterVisibility(bool show)
 }
 
 //----------------------------------------------------------------------------
-void vtkF3DUIActor::SetFpsValue(int fps)
+void vtkF3DUIActor::UpdateFpsValue(const double elapsedFrameTime)
 {
-  this->FpsValue = fps;
+  this->TotalFrameTimes += elapsedFrameTime;
+  this->FrameTimes.push_back(elapsedFrameTime);
+
+  while (this->TotalFrameTimes > 1.0)
+  {
+    double oldestFrameTime = this->FrameTimes.front();
+
+    this->FrameTimes.pop_front();
+    this->TotalFrameTimes -= oldestFrameTime;
+  }
+
+  double averageFrameTime = this->TotalFrameTimes / this->FrameTimes.size();
+  this->FpsValue = static_cast<int>(std::round(1.0 / averageFrameTime));
 }
 
 //----------------------------------------------------------------------------

vtkext/private/module/vtkF3DUIActor.h

@@ -9,6 +9,7 @@
 #define vtkF3DUIActor_h
 
 #include <vtkProp.h>
+#include <deque>
 
 class vtkOpenGLRenderWindow;
 
@@ -81,10 +82,10 @@ class vtkF3DUIActor : public vtkProp
   void SetFpsCounterVisibility(bool show);
 
   /**
-   * Set the fps value
+   * Updates the fps value
    * 0 by default
    */
-  void SetFpsValue(int fps);
+  void UpdateFpsValue(const double elapsedFrameTime);
 
   /**
    * Set the font file path
@@ -164,6 +165,11 @@ class vtkF3DUIActor : public vtkProp
   bool ConsoleBadgeEnabled = false;
 
   bool FpsCounterVisible = false;
+
+  // deque instead of queue to allow for iteration
+  std::deque<double> FrameTimes;
+
+  double TotalFrameTimes = 0.0;
   int FpsValue = 0;
 
   std::string FontFile = "";