Finding FPS

[Bino]

How would I find the FPS of my program. Not the average, but just so I can display it on the screen while my program is running.

[xvs]

To get the current FPS rate, you need to have some function called exactly once every second (I dunno how in win32 nor in X). Have it do something like:
FPS_Rate = FPS_Counter;
FPS_Counter = 0;

Then every frame, increment FPS_Counter. FPS_Rate will contain the current FPS.

[Humus]

Here's two useful functions for this:

__inline __int64 GetCycleNumber(){
__asm {
RDTSC
}
}

int GetMHz(){
LARGE_INTEGER t1,t2,tf;
__int64 c1,c2;

QueryPerformanceFrequency(&tf);
QueryPerformanceCounter(&t1);
c1 = GetCycleNumber();
_asm {
MOV EBX, 5000000
WaitAlittle:
DEC EBX
JNZ WaitAlittle
}
QueryPerformanceCounter(&t2);
c2 = GetCycleNumber();

return (int) ((c2 - c1) * tf.QuadPart / (t2.QuadPart - t1.QuadPart) / 1000000);
}

Call GetMHz in the beginning of your app and save the value. Then do like this:

void Init(){
MHz = GetMHz();
}


void render(){
static LARGE_INTEGER last,current;
double FPS;

last = current;
render_your_scene();
current = GetCycleNumber();

FPS = ((double) (current - last)) / (1000000.0 * MHz);

}

[mike]

Does ANSI C not have a timer function that will allow me to know when one second is up?

if(timer()==1)
{
display FPS
reset FPS counter
reset timer
}

if ur making the program in windows, use settimer when your window is created. this will generate a WM_TIMER event every x amount of time (you set this to 1 second, of course). and when a WM_TIMER even occurs, simply save your framecount and reset the framecount to zero again.

[Divide Overflow]

You might also just take the average of say 10 frames.

start=time(NULL);
.
.
fpscounter++;
if(fpscounter >10)
{
fpscounter = 0;
end=time(NULL);
fps = 10 / (end - start);
start=time(NULL);
}

(untested, offcouz )

Anyway, that should work

--> Divide Overflow

[This message has been edited by Divide Overflow (edited 09-02-2000).]

well, on Windows you could try


render_function()
{
static long millisecs;
static int frames;
long t;

frames++;
if ((t =timeGetTime())-millisecs >= 1000) {
/* show the frames here */
....
frames = 0;
millisecs = t;
}

/* for a Linux/UNIX application try gettimeofday() */

[ngill]

or try this technique..

//pseudo code

gettime(a);
drawstuff();
gettime(b);
timediff=b-a; //in ms
fps=1000/timediff

THAT'S IT... Q.E.D.

[wolfman8k]

What header file and/or libraries does the function timeGetTime() need?

When I use timeGetTime I get this error:
error LNK2001: unresolved external symbol __imp__timeGetTime@0

Thanks,
wolfman8k

[This message has been edited by wolfman8k (edited 09-07-2000).]

[PeterParker]

Hi wolfman8k!
The easiest technic (in my opinion) for windows is the Message from HUMUS.
you only have to use two Statements and three variables:

LARGE_INTEGER before, after, ClockPerSec;
QueryPerformanceFrequency(&ClockPerSec);
..
QueryPerformanceCounter(&before);
DrawWorld();
QueryPerformanceCounter(&after);

float duration = ((float)after.QuadPart-before.QuadPart ) / ClocksPerSec.QuadPart;

float FPS=1/duration;
..

So duration is the time between before and after in miliseconds. This is the same Algo like Humus, but a little bit shorter and not the exact one he had written. But if you have questions, look at his posting it will work..
Greets, Peter