[Engine]Max FPS in frame counter displays an abnormally high value on the first frame

[doyoung413]

What is an issue?

When the application starts, the Max FPS value shown in the frame counter window displays an abnormally high number on the very first frame. As seen in the attached image, the average (Avg) FPS is measured at 257.8, but the Max FPS is recorded momentarily at a much higher value of 311.3 (240fps is max).

Expected Causes

• On the first frame, the delta time calculation may be unstable or result in a very small value due to the absence of a previous frame's data, causing a momentary spike in the FPS reading.
• It's possible that necessary resources are already loaded before the main rendering loop begins, making the workload for the first frame exceptionally light and leading to a temporarily high frame rate.

Expected Solutions

[doyoung413]

The statistical calculation method has been refactored to be more robust against outliers.
The Timer class no longer stores persistent minFps and maxFps member variables. It now only collects a history of recent raw FPS values.
The UI display function (ShowFpsGraph) is now responsible for calculating all statistics (Min, Max, Avg) on the fly each frame by analyzing the entire history of recent values.

[CubeBerry]

I suspect this issue happens due to frame spike. Especially this happens when frame rate is not limited. Tested V-Sync disabled on OpenGL by following code:

SDL_GL_SetSwapInterval(0);

This showed average 3000 frames per second. One recognized thing is that GPU usage was significantly low (also lower than CPU usage). I suspect CPU is so fast so that CPU keeps waiting for GPU to finish tasks. I expect Triple Buffering to mitigate this issue.

[CubeBerry]

I also acknowleged GPU usage is higher when frame rate is limited to 60 or 120. This might show why frame strike happens. Requires further research.