"Scott Hill" <sco### [at] innocentcom> wrote in message
news:3b5f5261@news.povray.org...
> "Gilles Tran" <tra### [at] inapginrafr> wrote in message
> news:3B5F250E.276DA256@inapg.inra.fr...
> > Scott Hill wrote:
> >
> > > Have you tried a higher pretrace_start setting ? I've found whacking
it
> > > right up to 1.00 for final renders gets rid of ugly rad artifacts...
> >
> > Actually all I've been using for a while is pretrace_start =
pretrace_end
> = 1
> > (in Megapov). The strangest thing is that I don't know what I'm losing
> doing
> > that.
> >
>
>     Well, the way I understand it, the rad pretrace settings are similar
to
> the mosaic preview settings, i.e. they're expressed as a percentage of the
> image width... So with start=end=1.00 you're saying "take one sample at
the
> image width and do no more"... I think... Yeah, I'm pretty sure this
> correct - if you set pretrace_start to 1.00 and pretrace_end to 0.50
you'll
> see the rad pretrace stage gets down to 'blocks' half the width of the
image
> before the final pass starts... 0.25 ends at blocks 1/4 of the width and
so
> on... So, it seems to follow that, for max rad quality you need to set
> pretrace_start=1.00 and pretrace_end=1/imagewidth... Having said that, the
> 'blocks' start getting kind of blurry when they get to around 4x4pixels,
no
> matter what the pretrace_end setting is...

Hmm this is an interesting discusion, I've been wondering what these
settings really do, the pov docs arn't much help here. I'll have to do some
testing to see how different settings affect different images, but I'm not
going to play with this image any more.

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