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In article <3c782d3c@news.povray.org>,
"Rune" <run### [at] mobilixnet dk> wrote:
> It is clipped before AA and there's a good reason.
>
> Suppose you have a really bright sphere (the sun). All pixels that hit the
> sun would be completely white no matter if the sun occupies a small or big
> amount of the pixel, simply because the high brightness would dominate in
> the average. The result would be that very bright objects would not look
> antialiased at all no matter how high quality AA settings you used.
Well, this explains why I never succeeded in getting stars to survive AA
by increasing their brightness...that was the exact effect I expected
and wanted. I can manually soften the sun's outline (media, or a dimmer
sphere visible just around its edges), eliminating the problem there,
but there doesn't seem to be any way to compensate for small
(sub-pixel), very bright objects getting obliterated by the antialiasing.
Maybe a smarter algorithm would be possible...if there are other
high-brightness pixels nearby, you are at the edge of a bright object,
so clip and supersample, otherwise supersample then clip.
--
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/
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In article <8JP### [at] lzernet>, jan### [at] lzernet (Jan Walzer) wrote:
> 4. proving (of course, not a mathiematical proove) right, with my former
> statement, that every known AA-Algo can be broken with a scene ...
Just use an infinite number of samples per pixel. I don't have the CPU
power to test this though, ask God. ;-)
Actually, that might not be enough, because you still have the grid of
pixels...how about creating a neural net to detect the moire patterns
and compensate for them?
Or just reduce the pixel size to near-microscopic. Then you won't even
need antialiasing. ;-)
Really, I think resolutions are going to make a jump soon, so
antialiasing won't be as big a requirement.
--
Christopher James Huff <chr### [at] maccom>
POV-Ray TAG e-mail: chr### [at] tagpovrayorg
TAG web site: http://tag.povray.org/
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"Christopher James Huff" wrote:
> Maybe a smarter algorithm would be possible...if
> there are other high-brightness pixels nearby,
> you are at the edge of a bright object, so clip
> and supersample, otherwise supersample then clip.
I have had similar considerations, but have not managed to get any further
than wondering what method could be used. I don't think it will be trivial,
and there'll always be cases where you get an opposite behavior of what you
want.
If a smart behavior isn't possible, I prefer the current one. The current
method works the same way as if you rendered the image at huge resolution
and then scaled it down.
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Feb 16)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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Jan Walzer wrote:
>
> > This reminds me...are the colors clipped before or after antialiasing?
> > It should be after...a "superbright" object (rgb > 1) should contribute
> > more to a pixel than a dim (rgb 1) one.
>
> IMHO it would be a _MAJOR_ design-flaw, if it wouldn't be this way ...
In beta 11 ambient sphere of rgb 1 and rgb 100 produce the exact same
image when rendered with +am2 +a0.0 +j0.0. Also DOF produces
same image for both cases. The colors are clipped before aa
and DOF calculations :(
_____________
Kari Kivisalo
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Rune wrote:
>
> It is clipped before AA and there's a good reason.
It's not realistic.
_____________
Kari Kivisalo
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"Kari Kivisalo" wrote:
> Rune wrote:
> >
> > It is clipped before AA and there's a good reason.
>
> It's not realistic.
You can't talk about realistic. AA doesn't happen in nature... ;)
The current AA give the same result as if you rendered the image at a very
large resolution and then scaled it down. I think that's what AA is meant to
do. It gives smooth results. the way you'd like it to work, it wouldn't
always give smooth results, often things would look like they had not been
antialiased at all.
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Feb 16)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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Rune wrote:
>
> You can't talk about realistic. AA doesn't happen in nature... ;)
Take a picture either with a film or ccd camera of a 10 candela source.
Compare that to picture of a 1000 candela source with same exposure.
You say they would look the same.
We are making _digital_ images. Even digital images of nature have
been subject to aa or lpf at some point. In real life the clipping
occurs at the image detector/film, not before. The aa/lpf operates
on the unclipped intensities. Would be hard to make it work the other
way around :)
_____________
Kari Kivisalo
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From: Tony[B]
Subject: Re: looking for antialiasing critical scenes
Date: 24 Feb 2002 08:03:46
Message: <3c78e4b2@news.povray.org>
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Wow. I'm impressed. Your new methods look very good. Can you conduct a few
tests on more complete scenes? It would also be nice if you could explain
how you acheived each one so some more discussion about them can be had.
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From: Micha Riser
Subject: Re: looking for antialiasing critical scenes
Date: 24 Feb 2002 08:18:20
Message: <3c78e81b@news.povray.org>
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Tony[B] wrote:
> Wow. I'm impressed. Your new methods look very good. Can you conduct a few
> tests on more complete scenes? It would also be nice if you could explain
> how you acheived each one so some more discussion about them can be had.
If you have a particular scene that you want to have tested you can send it
to me and I will test it. I still want to do some modifications to my
implementations. Once I have finished that I will make a detailed
explanation how they work.
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"Kari Kivisalo" wrote:
> We are making _digital_ images. Even digital images of
> nature have been subject to aa or lpf at some point.
Photos are not subject to antialiasing I think. They are subject to focal
blur and probably other types of blurring that I don't know about. (Is that
what lpf mean?) But blurring has nothing to do with antialiasing. Blurring
(in nature) is resolution independent and covers many pixels, while
antialiasing is highly resolution dependent and has to do with individual
pixels.
Rune
--
3D images and anims, include files, tutorials and more:
Rune's World: http://rsj.mobilixnet.dk (updated Feb 16)
POV-Ray Users: http://rsj.mobilixnet.dk/povrayusers/
POV-Ray Webring: http://webring.povray.co.uk
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