Peter Popov wrote:
> 
> On 26 Sep 2000 15:57:28 -0400, ron### [at] povrayorg (Ron Parker)
> wrote:
> 
> >>So, when anti-aliasing, how should POV treat rays that hit the
> >>background? Ignore them?
> >
> >No, average them in as pure alpha.  Rune has the right idea.
> 
> Rune proposes that they should be ignored in the color channels and
> only the alpha channel carried information about them. This would make
> more sense if a) the background color is stored in the image somehow
> (I like Rune's idea about 100% transparent pixels) and b) sky_sphere
> is not used. I dont' really know how this will affect fog, global
> media and rainbow effects. I am pretty sure it will mess the former
> two up, though.
> 

a) Only meaningfull if you do not want any alpha.
If I request the alpha channel, the background is only a 
placeholder for the directview in POV. If I intended
to have a picture with an alpha channel, you can assumed
that I will be able to use it in the generated picture.
So 100% transparent pixel does not need to adapt their
color to the background of the pov-script.

b) If sky_sphere is used, how can you have any alpha information ?
I do not understand how it could happen (No ray reach infinity,
they hit the sky_sphere first, hence, I suppose, no transparency
in the alpha channel.)

So basically, I currently agree with Rune & Ron Parker.

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