POV-Ray : Newsgroups : povray.general : Tracking down slow renders : Re: Tracking down slow renders Server Time
10 Dec 2023 12:08:31 EST (-0500)
  Re: Tracking down slow renders  
From: Chris R
Date: 8 May 2023 10:05:00
Message: <web.6459015c5485baa9159bf83b5cc1b6e@news.povray.org>
"Kenneth" <kdw### [at] gmailcom> wrote:
> "Chris R" <car### [at] comcastnet> wrote:
> >
> > What I'm afraid of is that some interaction
> > between anti-aliasing, radiosity, and reflection is causing an infinite loop
> > measuring against thresholds.
> >
> That's a really hard-core set of features to throw at POV-ray all at once, ha.
> Especially with isosurfaces added to the mix. I have similar scenes where I had
> to eliminate anti-aliasing altogether, if I didn't want to exclusively tie up my
> machine for days...and this on an 8 core/16 thread machine!
> My gut-feeling is that the slowdown for your last block is AA-related.
> One suggestion would be to reduce the size of your Render_Blocks. The default is
> 32X32 pixels, I think. I run complex-feature scenes at 8X8, which does improve
> the overall rendering speed on multi-core machines, and *helps* to keep that
> final render block from taking so much time. As Thorsten F. pointed out in an
> earlier post last year, each Render_Block uses an individual core (or thread-- I
> get the two confused.) By reducing the block size, the processor seems to work
> more efficiently, and doesn't have to spend all of its time on a single block
> (with a single core) while the other cores are sitting idle. Or something like
> that!
> I may have the technicalities wrong, but a smaller block size can sometimes
> speed-up the render. It definitely works for media and isosurfaces (but I'm not
> patient enough to throw in AA as well; most of my renders lately are just
> relatively quick tests of one thing or another.)

Thanks for the suggestion.  I had done that in the past, but forgot about it.  I
should just make it my default instead since it would probably help most of my
renders anyway.

I'm going to try some of the other suggestions as well.  The latest render
completed 99% in about 2 hours, and then just sat there for 2 days on the last 2
blocks.  I'm afraid without any other adjustments, I'll get to 99.9% using
smaller blocks, but that last 0.1% will then take two days.

-- Chris R.

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