Calculate Frames Per Second

try something like:

int nFramesPerSecond=(int)(1000.f/fTimeDifference);

What uncutno said. Also, if the actual time difference is very small, GetTickCount() may not be accurate enough for you. GetTickCount() returns miliseconds, but I seem to recall that it is not actually guaranteed to be updated at anything all that close to once a milisecond. You might try QueryPerformanceFrequency() and QueryPerformanceCounter() instead.

My solution is probably more accurate, but less instant:

int lastFPSlog = 0;
int frames = 0;
int fps = 0;

while (true) {

// Renderer code

++frames;

int time = SDL_GetTicks();
if (time > lastFPSlog+1000) {
fps = frames;
frames = 0;
lastFPSlog = time;
printf("FPS: %i\n",fps);
}
}

That way it only updates once a second, but is more accurate.

Quote:

Original post by mumpo What uncutno said. Also, if the actual time difference is very small, GetTickCount() may not be accurate enough for you. GetTickCount() returns miliseconds, but I seem to recall that it is not actually guaranteed to be updated at anything all that close to once a milisecond. You might try QueryPerformanceFrequency() and QueryPerformanceCounter() instead.

To add more informations: GetTickCount() granularity is known by using GetSystemTimeAdjustment(). AFAIR it is close to 10ms.

Regards,

Use a wrapper class around your timer services. It you have a high-resolution timer, use QueryPerformanceCounter. If that fails, maybe use the multimedia timer (timeGetTime), which has the potential to be set to use a higher resolution than GetTickCount for a short time. And lastly, resort to GetTickCount.

However if this is just for a FPS counter, messing with high-resolution timers is just overkill. They'd be more useful if you were writing a code profiler where you actually have to measure each individual block of code. I personally just update my FPS counter once a second. You get a nice, clean value because you're counting frames ever second, not taking the inverse of elapsed time every frame.

Maybe I'm missing something but aren't your units in ms? So 1000/0.1 isn't 10,000 frames per second but 10,000 frames per millisecond = 10 frames per second.

Here is a simple tutorial showing FPS from GameTutorials.

Quote:

Original post by Drethon Maybe I'm missing something but aren't your units in ms? So 1000/0.1 isn't 10,000 frames per second but 10,000 frames per millisecond = 10 frames per second.

1000ms = 1 second

1000ms/1000ms = 1 frame for this second, ie 1 fps

EDIT: I am using c++ and Direct3D9

Quote:

Original post by benryves My solution is probably more accurate, but less instant: int lastFPSlog = 0; int frames = 0; int fps = 0; while (true) { // Renderer code ++frames; int time = SDL_GetTicks(); if (time > lastFPSlog+1000) { fps = frames; frames = 0; lastFPSlog = time; printf("FPS: %i\n",fps); } } That way it only updates once a second, but is more accurate.

Hey, I was wondering. The bit were you have 'while(true)'. While what is true?

timeGetTime can get 1 ms accuracy by using timeBeginPeriod(1); in create function and timeEndPeriod(1); in destroy function. It's very important to remember the last one, because normally it only updates every 10 ms or so.

Technically, you only request a 1 ms update time. It will return TIMERR_NOCANDO if it isn't possible.

Quote:

Hey, I was wondering. The bit were you have 'while(true)'. While what is true?

Nothing in particular. It will just keep looping until the program is terminated.

Quote:

Original post by utilae Hey, I was wondering. The bit were you have 'while(true)'. While what is true?

That's just a way to make an infinite loop. true is just a statement the same as any other conditional test that will resolve to a true or false. In his example, that's just the game loop that will run forever until the game exits.

Here is an exampel of using QueryPerformanceFrequency()

__int64  timerFreq;           // How many counts in a second.__int64  startTime, endTime;  // Start and ends timesfloat    fps;if(QueryPerformanceFrequency((LARGE_INTEGER *)&timerFreq) != 0){  QueryPerformanceCounter((LARGE_INTEGER *)&startTime);  ....  QueryPerformanceCounter((LARGE_INTEGER *)&endTime);  fps = (float)((double)timerFreq / ((double)(endTime - startTime)));}

Thant should do it