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| Calculate Frames Per Second |
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utilae Member since: 12/8/2004 From: Dargaville, New Zealand |
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 Posted - 1/10/2005 12:47:32 AM |
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| Hi I want to calculate the frames per second, so i can display it on screen. Right now I do the following: //start time DWORD dwTimeStart=GetTickCount(); //. //.after a while //. //time difference between start and end(now) float fTimeDifference=GetTickCount()-dwTimeStart; if(fTimeDifference==0)fTimeDifference=0.1; //1000ms divide by time difference in ms int nFramesPerSecond=1000/fTimeDifference; My problem is that fTimeDifference=0, so I detect that and set it to 0.1, giving me 10,000 frames per second!!! I'm wondering if I am doing this wrong or something. |
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uncutno Member since: 4/4/2001 From: Norway |
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Posted - 1/10/2005 1:14:31 AM |
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| try something like: int nFramesPerSecond=(int)(1000.f/fTimeDifference); |
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mumpo Member since: 9/25/2004 From: Los Angeles, CA, United States |
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Posted - 1/10/2005 1:26:50 AM |
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| 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. |
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benryves GDNet+ Member since: 9/4/2003 From: Purley, United Kingdom |
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 Posted - 1/10/2005 9:31:47 AM |
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| 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. |
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Emmanuel Deloget GDNet News Lead Member since: 8/27/2003 From: France |
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Posted - 1/10/2005 9:48:39 AM |
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Quote: To add more informations: GetTickCount() granularity is known by using GetSystemTimeAdjustment(). AFAIR it is close to 10ms. Regards, -- Emmanuel D. [blog, in French] [blog, very bad googlized translation] [NEW: English version of teh blog! (WIP)] |
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Zipster GDNet+ Member since: 3/11/2000 From: Las Vegas, NV, United States |
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Posted - 1/10/2005 10:19:46 AM |
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| 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. |
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Drethon Member since: 11/29/2004 From: Grand Rapids, MI, United States |
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Posted - 1/10/2005 10:36:22 AM |
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| 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. |
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Drew_Benton GDNet+ Member since: 7/29/2004 From: Katy, TX, United States |
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Posted - 1/10/2005 11:26:06 AM |
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| Here is a simple tutorial showing FPS from GameTutorials. |
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utilae Member since: 12/8/2004 From: Dargaville, New Zealand |
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Posted - 1/10/2005 4:20:40 PM |
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Quote: 1000ms = 1 second 1000ms/1000ms = 1 frame for this second, ie 1 fps EDIT: I am using c++ and Direct3D9 |
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utilae Member since: 12/8/2004 From: Dargaville, New Zealand |
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Posted - 1/10/2005 4:28:02 PM |
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Quote: Hey, I was wondering. The bit were you have 'while(true)'. While what is true? |
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nife Member since: 4/6/2004 From: Denmark |
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Posted - 1/10/2005 4:28:31 PM |
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| 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. |
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Zipster GDNet+ Member since: 3/11/2000 From: Las Vegas, NV, United States |
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Posted - 1/10/2005 4:46:43 PM |
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| Technically, you only request a 1 ms update time. It will return TIMERR_NOCANDO if it isn't possible. |
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GodlyGamr Member since: 9/15/2003 From: Huntingdon Valley, PA, United States |
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Posted - 1/10/2005 7:52:07 PM |
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Quote: Nothing in particular. It will just keep looping until the program is terminated. |
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helix Member since: 9/11/2002 From: Kirkland, WA, United States |
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Posted - 1/13/2005 11:37:54 PM |
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Quote: 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. |
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MrRage Member since: 8/7/2004 |
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Posted - 1/14/2005 11:55:18 AM |
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Here is an exampel of using QueryPerformanceFrequency()
__int64 timerFreq; // How many counts in a second.
__int64 startTime, endTime; // Start and ends times
float 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 |
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| All times are ET (US) |
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