Calculating frames per second in a game

Question

What\'s a good algorithm for calculating frames per second in a game? I want to show it as a number in the corner of the screen. If I just look at how long it took to render

Answer 1

This might be overkill for most people, that's why I hadn't posted it when I implemented it. But it's very robust and flexible.

It stores a Queue with the last frame times, so it can accurately calculate an average FPS value much better than just taking the last frame into consideration.

It also allows you to ignore one frame, if you are doing something that you know is going to artificially screw up that frame's time.

It also allows you to change the number of frames to store in the Queue as it runs, so you can test it out on the fly what is the best value for you.

// Number of past frames to use for FPS smooth calculation - because 
// Unity's smoothedDeltaTime, well - it kinda sucks
private int frameTimesSize = 60;
// A Queue is the perfect data structure for the smoothed FPS task;
// new values in, old values out
private Queue frameTimes;
// Not really needed, but used for faster updating then processing 
// the entire queue every frame
private float __frameTimesSum = 0;
// Flag to ignore the next frame when performing a heavy one-time operation 
// (like changing resolution)
private bool _fpsIgnoreNextFrame = false;

//=============================================================================
// Call this after doing a heavy operation that will screw up with FPS calculation
void FPSIgnoreNextFrame() {
    this._fpsIgnoreNextFrame = true;
}

//=============================================================================
// Smoothed FPS counter updating
void Update()
{
    if (this._fpsIgnoreNextFrame) {
        this._fpsIgnoreNextFrame = false;
        return;
    }

    // While looping here allows the frameTimesSize member to be changed dinamically
    while (this.frameTimes.Count >= this.frameTimesSize) {
        this.__frameTimesSum -= this.frameTimes.Dequeue();
    }
    while (this.frameTimes.Count < this.frameTimesSize) {
        this.__frameTimesSum += Time.deltaTime;
        this.frameTimes.Enqueue(Time.deltaTime);
    }
}

//=============================================================================
// Public function to get smoothed FPS values
public int GetSmoothedFPS() {
    return (int)(this.frameTimesSize / this.__frameTimesSum * Time.timeScale);
}