"White Ryder" <nomail@nomail> wrote in message 
news:web.43fce6995f972968fc5d75160@news.povray.org...
> I'm rendering a sequence of frames in which certain objects in the scene
> rotate, but most of the scene stays the same from frame to frame.

If AA is being used there's a chance that could influence render time by an 
observable amount, also such things as refraction and reflection might make 
a significant change.

> I just happened to be looking at the Messages window during the rendering,
> and noticed that each frame seems to take longer than the last to render.
> E.g. the first frame took 15 minutes, the next took 17, and so on until
> 8 or 9 frames later it was taking 28 minutes.
>
> This would be understandable to me if the scene were changing in 
> complexity
> from one frame to the next, but as far as I can tell it is equally complex
> in each frame.

Even so, as I said at first, there could be a possibility of AA and other 
factors causing a difference in render times as the objects move. Of course, 
I'm mostly guessing at this.

> Has anyone noticed this phenomenon before?  I saw there was a thread 
> earlier
> this month asking about increasing amounts of RAM being used in each 
> frame;
> it's possible the two issues are related (I haven't been watching the RAM
> usage).  However, I'm using v3.6, not v3.5.

There's more than one version 3.6 so that could be a factor somehow. Latest 
is 3.6.1b, with 1a before that, and again 3.6.0 before that. Can't recall 
how many were actually released to the public.

> 8<---snip---8< the first time it ran with Default (radiosity)
> it took four hours to render, but later when it ran with Default again it
> took less than 1/2 an hour.

That's a big difference. I'd say background processes running at the same 
time during part of it could possibly explain it, if not POV itself doing 
something to slow it down or speed it up.

> Does anyone know of anything that POV-Ray
> does while rendering an animation sequence that would explain why very
> similar frames would take successively longer to render?

I know this has been a subject of discussion in the past, unfortunately I 
don't remember anything concrete about it. I also searched (only this 
newsgroup) for something similar, although I didn't find anything to point 
you to. I can vaguely recall something about loading of image maps or maybe 
a writing of temporary files being an issue with rendering in succession, 
I'm just not absolutely positive about anything so I'll leave this to others 
to talk about.

Be sure to check your version there, anyhow, in the Help|About or when first 
starting POV. More often than not it helps everyone else to know precisely 
which you're using.

Bob H

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