> Because they're too small to be accurately represented in the final image
> resolution. Just because they're intense doesn't mean they should become a
> full pixel in size. This could end up producing different results depending
> on what the final resolution is.

But what about if you take a photo of the night sky? The stars are much smaller
than 1 pixel, however they show up because of their intensity.

The colour of a pixel should be the average colour across the area of that
pixel, so if you have a star that's 1/2000th the area of the pixel and has
intensity 1000, then the pixel should have a colour of rgb 0.5. This happens in
a camera because it takes theoretically infinite samples (i.e. all the photons
hitting that pixel contribute to the brightness).

I believe that's the effect Bob was trying to simulate.

-- 
Tek
www.evilsuperbrain.com

"Slime" <fak### [at] emailaddress> wrote in message news:400409cc$1@news.povray.org...
> > No, do I mean unfortunately. Clipping before antialiasing is the wrong
> > way to fix this problem. Small, intense sources get completely wiped
> > out.
>
> Because they're too small to be accurately represented in the final image
> resolution. Just because they're intense doesn't mean they should become a
> full pixel in size. This could end up producing different results depending
> on what the final resolution is.
>
> > Antialiasing supersamples the scene, not some virtual model of an
> > image file in a format that's limited to a tiny dynamic range.
>
> Antialiasing supersamples the scene, but it must take into account that the
> final output will have limitations such as a finite dynamic range. The
> mysterious "format" you refer to is the same as the actual format of the
> final image, which is important. By clipping before averaging, anti-aliasing
> produces the effect of rendering at an infinite resolution and then resizing
> smaller, which is exactly what it's supposed to do.
>
> I admit that I do see some logic in your argument - clipping before
> averaging does feel artificial to some extent. However, the fact that
> clipping after averaging would produce jagged edges on bright objects causes
> me to believe that it would be much more useless than clipping before
> averaging.
>
> In any case, I'd appreciate if someone who's done a significant amount of
> research on the topic could step in and tell us *why* POV-Ray does it the
> way it does, and maybe what other popular 3D apps do, and why it is or is
> not correct.
>
>  - Slime
>  [ http://www.slimeland.com/ ]
>
>

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