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Baffling Framerates

Started by mattm Feb 23, 2005 at 4:14 PM 4 replies 850+ views

Original Post

Feb 23, 2005 at 4:14 PM

Hi, I am getting very confusing framerate; sometimes they are reporting as 65 frames a second (1 shader, about 1200 vertices) and other times (exactly the same scene and code etc) they report as 320!! My frame calculation is based on

float fCurrTime = (float)timeGetTime();
      float fDeltaTime = (fCurrTime - mfLastTime)*0.001f;
      cState* pCurrentState = mpStateManager->GetState();
      pCurrentState->ProcessFrame(fDeltaTime);
      mfLastTime = fCurrTime;

and

TimeElapsed += dTime;

	if(TimeElapsed >= 1.0f)
	{
		FPS = (float)FrameCnt / TimeElapsed;

		sprintf(FPSString, "%f", FPS);
		//sprintf(FPSString, "%f", dTime);
		FPSString[8] = '\0'; // mark end of string

		TimeElapsed = 0.0f;
		FrameCnt    = 0;
	}

any ideas? Thanks, Matt

Trip99

Feb 23, 2005 at 4:29 PM

I cannot see where dTime is defined. You have a fDeltaTime but no dTime. The general idea seems right though so the problem may be elsewhere. BTW: you do not need to null terminate a string created with sprintf as it does it itself.

mattm

Author

mattm

Feb 23, 2005 at 4:31 PM

Sorry, the second piece of code is in a different class. dTime is simply the local incarnation of fDeltaTime in pCurrentState->ProcessFrame(fDeltaTime).

dma42

Feb 24, 2005 at 2:39 AM

where do you increase the FrameCnt-variable?

mattm

Author

mattm

Feb 24, 2005 at 8:20 AM

Just above the code you can see..sorry :)

If i display the interval between frames this also changes between 0.003 to 0.004 and 0.015 -to 0.016, which ties in with the framerates reported. I even had one go where they started reporting 63 and jumped to about 350 before staying there!

This is really confusing!

Matt

dma42

Feb 27, 2005 at 9:29 AM

May be you should use the functions QueryPerformanceCounter and QueryPerformanceFrequency instead of timeGetTime. (They are more accurate).

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dma

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