Thanks for the quick response Jerry. Yes I agree that it is saving some time
by not anti-aliasing the unused lines.

I had a closer look and although the anti-aliasing is done by shooting extra
rays through the pixels on each "used" line, it first needs to decide
whether a particular pixel actually needs to be anti-aliased in the first
place. It does this by comparing the calculated colour of the pixel with its
neighbour to the left and ABOVE! Thus it needs to know the colour of the
pixel on the "unused" line above, but it seems that it doesn't actually use
the neighbouring pixels to perform the anti-aliasing itself.

Colin

"Jerry" <jer### [at] acusdedu> wrote in message
news:jer### [at] netplexaussieorg...
> Colin wrote:
> > Is there anyone who knows how povray is supposed to perform antialiasing
> > when field rendering is switched on?
>
> I'm not quite sure, but I think this is the way that it has to work.
> Anti-aliasing requires knowing the colors of surrounding pixels, and
> that includes pixels to the top and the bottom. The only way to know
> them is to calculate them.
>
> Note that from your description, POV *is* saving time when you field
> render with anti-aliasing switched on: it isn't anti-aliasing the
> "unused" lines.
>
> Jerry
> --
> http://www.hoboes.com/jerry/
> "Give a man a fish and you feed him for a day. Teach him to fish, and
you've
> depleted the lake."--It Isn't Murder If They're Yankees
> (http://www.hoboes.com/jerry/Murder/)

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