c++ - C++：计算移动 FPS

Question

我想计算游戏最后 2-4 秒的 FPS。最好的方法是什么？

谢谢。

编辑：更具体地说，我只能访问一个以一秒为增量的计时器。

Answer 1

Near miss of a very recent posting. See my response there on using exponential weighted moving averages.

C++: Counting total frames in a game

Here's sample code.

Initially:

avgFps = 1.0; // Initial value should be an estimate, but doesn't matter much.

Every second (assuming the total number of frames in the last second is in framesThisSecond):

// Choose alpha depending on how fast or slow you want old averages to decay.
// 0.9 is usually a good choice.
avgFps = alpha * avgFps + (1.0 - alpha) * framesThisSecond;

Answer 2

Here's a solution that might work for you. I'll write this in pseudo/C, but you can adapt the idea to your game engine.

const int trackedTime = 3000; // 3 seconds
int frameStartTime; // in milliseconds
int queueAggregate = 0;
queue<int> frameLengths;

void onFrameStart()
{
    frameStartTime = getCurrentTime();
}

void onFrameEnd()
{
    int frameLength = getCurrentTime() - frameStartTime;

    frameLengths.enqueue(frameLength);
    queueAggregate += frameLength;

    while (queueAggregate > trackedTime)
    {
        int oldFrame = frameLengths.dequeue();
        queueAggregate -= oldFrame;
    }

    setAverageFps(frameLength.count() / 3); // 3 seconds
}

Answer 3

可以为最后 100 帧保留帧时间的循环缓冲区，并对它们进行平均吗？那将是“最后 100 帧的 FPS”。（或者，更确切地说，99，因为您不会区分最新时间和最旧时间。）

调用一些准确的系统时间，毫秒或更好。

Answer 4

你真正想要的是这样的（在你的 mainLoop 中）：

frames++;
if(time<secondsTimer()){
  time = secondsTimer();
  printf("Average FPS from the last 2 seconds: %d",(frames+lastFrames)/2);
  lastFrames = frames;
  frames = 0;
}

如果您知道如何处理结构/数组，您应该很容易将此示例扩展到 4 秒而不是 2 秒。但是如果您需要更详细的帮助，您应该真正提及为什么您无法获得精确的计时器（哪种架构，语言） - 否则一切都像猜测......