"Christopher James Huff" wrote:
> Rune wrote:
> > You can't talk about realistic.
> > AA doesn't happen in nature... ;)
>
> But it is intended to calculate a specific thing
> (the color over the entire pixel), and clipping
> makes that less accurate.

No, it's a definition issue. The current definition of AA in POV-Ray is that
it is intended to calculate the average clipped color over the entire pixel
and it does that 100% accurately according to the definition.

If you want to change the definition, that can be discussed, but the current
behavior is not flawed or inaccurate in any way as it does exactly what it's
intended to do.

> And it apparently also happens with focal blur...not good!

I agree there. Focal blur is a completely different issue, and it should
take the unclipped colors as input. (And then we could get cool lens effects
without "cheating"!)

BTW, as I see AA and focal blur as two separate things, I think it should be
possible to use both at the same time (though it would be slow). I have
never understood why it's not possible.

> I'd gladly take having unantialiased edges on superbright
> objects to have them work properly in other cases...

But I wouldn't. I want my AA to smooth edges without exception. That's what
AA is for. To average colors is not the goal, it's just a mean to reach the
goal. The goal is smooth edges.

> It also seems unintuitive to me: you have a bunch of
> small stars, and antialiasing wipes them out because
> they don't cover whole pixels. You make them brighter
> to compensate...nothing happens?!?

Exactly what would happen if you rendered the image at a large resolution
and then scaled it down. You get smooth results. If your very bright stars
covered several pixels each, they would be completely jaggy using your
method. To me that's not intuitive when I have turned on AA to get smooth
results.

> And with focal blur, the problem is worse...you simply will
> get a less realistic image.

I agree.

> Maybe some flag to limit the max value of a sample...

You mean that the user should be able to change the value that samples are
clipped to, which is currently one? I wouldn't mind as long as the current
behavior keeps being the default.

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/
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