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Re: Of time scaling and FPS

Miguel A. Osorio wrote:

> Steve Baker wrote:
>>"Miguel A. Osorio" wrote:
>>> Anyway, on to the FPS problem. Using the method described above, I use
>>>delta to scale my time-dependent variables, in order to get some smooth
>>>animation. Thing is, I don't. The whole animation looks all jagged up,
>>>without using time scaling it goes on fine; do note that, however, I
>>>don't know why, the FPS mark keeps jumping about *all the time*, it
>>>never settles on some average. Does anyone know a reason for this? Or am
>>>I doing the whole time scaling calculation the wrong way?
>>Probably - yes.  It's easy to overlook some variable that needs to be
>>scaled by the time-step.
>>That doesn't explain why your rendering time is fluctuating so much though.
> 	Yes, even though I *may* have overlooked some variable that would need
> the delta scaling, which I don't believe is the case, since the whole
> demo is just a very small program with just a few time dependent
> variables, it still doesn't explain the heavy fluctuation. I notice that
> some hard disk syncronizing mechanism in Linux kind of lags the whole
> thing periodically, but aside from that, my frame rate is still too
> jittery.
> 	I noticed I get smoother rates on running the demo on Windows, but I
> still think there's something wrong lurking around somewhere. Oh, and
> since we're talking strange here, how about this: another thing I
> noticed was that the whole average frame rate (even with excessive
> jittering) is different every time I run the damn thing! Crap! :)

Hm... is it possible that there are a lot of background processes 
running on your machine. They all get active from time to time and that 
actually kills performance because they go active from time to time. 
Computers can loose about 10-20% of their computing power to them on 
average (at least that's what I've experienced so far).

I'm running my computers at home heavily loaded with services and get 
some irregular loop times regularly. But they haven't been jittering too 
much, though. Maybe the jitter is even caused by heavy network traffic 
your computer is forced to listen to (as could be the case in large 

Another source for the jitter could be the use of OpenGL with vsync. At 
least some drivers (I think NVidia's is one of them) tend to behave 
jittery. That's a problem Crystal Space is fighting with. But I haven't 
experienced that one myself yet.

> Miguel A. Osorio.


* Gregor Mueckl                 GregorMueckl@gmx.de *
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