This is a really common question. I don''t understand how someone could do something complex like making a graphical program and NOT know how calculate FPS. =)
Try searching the board a bit I''ve seen several examples before...

ello
sure it''s simple. I use the following lines of code , they''re probably "the worsest way" you should do it , but hey! , they seem to work quite fine for me

variables you use :
char fpsmsg[128]; - to generate text which goes onscreen
double time;-for time between start/end timing calls
double fps;-for fps according to start/end time (of course it''s fps of the piece of code you''re measuring the time for , in case it''s not your whole loop , it won''t be the real fps number but how many times per second you can run the piece of code you''re timing
__int64 t1,t2,freq;-values to keep time info

and here are the functions to start/end timing

void starttiming()
{
QueryPerformanceFrequency((LARGE_INTEGER *)&freq);
QueryPerformanceCounter((LARGE_INTEGER *)&t1);
}

void endtiming()
{
QueryPerformanceCounter((LARGE_INTEGER *)&t2);
time=(double)(t2-t1)/(double)(freq);
fps=(double)(freq)/(double)(t2-t1);
sprintf((char*)fpsmsg,"TIME: %f FPS: %3.3f",time,fps);
}

the starttimer simple gets current time and stores it in t1 for later. endtimer gets t2 time value and with a little bit of math calculates out needed data while sprintf makes it into a nice text message it gives accurate results for hungryds of frames per sec easily , so you don''t have to worry much , in case you want to test your whole code time (as to get the real fps value) simple use it like

mainloop
{
endtiming();
starttiming();
drawtext(fpsmsg);
}
and you''re done

the fps counter is a lil crazy and changes by a bit all the time , so you might rather want to sum fps rate from several frames and then show the value , and again after several frames change the shown value , else you will end up with a flickering fps counter which changes way too fast

hope it helps , have fun

#include
clock_t start, finish ;
double duration, frames, FPS ;

in your init function :
start = clock();

in your drawing function :
finish = clock() ;
duration += (double)(finish - start) / CLOCKS_PER_SEC ;
frames ++ ;
FPS = frames / duration ;
start = clock() ;

function to draw text on the screen (be sure to check NeHe tutorials to fully understand glRaster2*) :
void PrintFPS() {
char buffer[10] ;
int Nb = sprintf(buffer, " FPS : %3.1f", FPS) ;
glRasterPos2i(0, 0) ;
for (int i = 0; i < Nb; i++) glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, buffer) ;
}

here it is, but you''ll have to perfect this a code a bit because GLUT render a frame only when needed (resize, mouse event, ...). So you surely will need to add code in your idle function (glutIdleFunc)

that''s all

thanks to anonymous poster for the code.
i implemented this in something i''m working on and modified it to do the averaging. the code below averages it over 6 frames.
I''m kinda new to c and programming in general so if anyone sees any optimizations or anything please feel free to post an update ( i think it''s elegant enough )


void EndTiming()
{
static unsigned short int i = 0;
static double fAvgFps[6];

QueryPerformanceCounter((LARGE_INTEGER *)&ldTime2);
fTime = (double)(ldTime2-ldTime1)/(double)(ldFrequency);
fFps = (double)(ldFrequency)/(double)(ldTime2-ldTime1);

fAvgFps = fFps;

if( i == 5 )
{
for( int foo = 0; foo <= 5; foo++ )
fAvgFps[6] += fAvgFps[foo];

fAvgFps[6] = ( fAvgFps[6] / 6 );
i = 0;
sprintf( (char*)szFps," FPS: %3.1f", fAvgFps[6] );
}
else i++;
}