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30ms for Clear()?!

Started by Zaei Dec 1, 2001 at 2:35 PM 6 replies 700+ views

Original Post

Dec 1, 2001 at 2:35 PM

I have a feeling that something is seriously wrong. If i run a render loop containing:

  
start = GetTickCount();
Clear(0) // clears the screen to black


Flip() // flips to the screen...

end = GetTickCount();

end - start == 0..30ms, averaging around 20..24ms. I have the Retail runtimes selected in the Control panel thingie as well. Im running Win2k, with an ATI RagePro (i know, its terrible, but not this bad), ~550 p3, with the HAL device. Any help would be much appreciated. Z.

Null and Void

Dec 1, 2001 at 2:39 PM

Flip has to wait for V-Sync. Also, GetTickCount has horrible accuracy, there''s no way you''ll get the correct about of time using it.

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Zaei

Dec 1, 2001 at 4:05 PM

Its accurate enough to tell me that something is wrong. Clear is usually ~0ms, and suddenly its ~30.

Z.

Kippesoep

Dec 1, 2001 at 4:41 PM

Yeah, the accuracy is that bad. And the actual call to GetTickCount is also very slow. I am working on a game full of graphics code, AI code and game logic and the very few calls to the Windows timer accounted for 2.7% of total execution time. If you want to time your stuff, use the performance counter (see QueryPerformanceCounter in msdn).

Also, it is very likely that the V-sync is what is actually killing your framerate.

And finally, "I wish the Rage Pro would just go away and die". That''s what an ATI employee told me at ECTS last August...

Zaei

Dec 1, 2001 at 4:54 PM

I wish my Rage Pro would die too. But it is definatly not my counter, beacuse it is accurate within 10ms (i get 0, 10, 20 and 30 as return values, mostly 30, when it should be mostly 0, with a few 10s thrown in).

The refresh rate on my moniter is set to 100 Hz. Would that account for 30ms?

Z.

Zaei

Dec 1, 2001 at 5:04 PM

Heh, removed the little _VSYNC from my swap effect, and that kinda halved that 30ms. Thanks guys =).

Z.

Moe

Dec 1, 2001 at 5:36 PM

Just out of curiosity, is timeGetTime() just as horrible for accuracy?

Null and Void

Dec 1, 2001 at 6:03 PM

quote:
Original post by Moe
Just out of curiosity, is timeGetTime() just as horrible for accuracy?

It isn''t great, but it''s better than GetTickCount.

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