When POVRay uses AA, does it use the actual colours and relative brightness
or the clipped colour? (i.e., do pigment values > 1 have more influence than
those 1 or less)

-tgq

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Never mind, I spoke too quickly and figured it out myself.
(yes it does use the full value not the clipped one)

-tgq

"Trevor Quayle" <Tin### [at] hotmailcom> wrote in message
news:3bd072ea$1@news.povray.org...
> When POVRay uses AA, does it use the actual colours and relative
brightness
> or the clipped colour? (i.e., do pigment values > 1 have more influence
than
> those 1 or less)
>
> -tgq
>
>
>
>

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> (yes it does use the full value not the clipped one)

Does it? It would make more sense to use the clipped value, I think. What AA
simulates is as though you had rendered the file at an infinite resolution
and then scaled it down to a finite resolution. By that definition, which
makes the most sense to me, it should clip the values first.

- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]

"Trevor Quayle" <Tin### [at] hotmailcom> wrote in message
news:3bd07478$1@news.povray.org...
> Never mind, I spoke too quickly and figured it out myself.
> (yes it does use the full value not the clipped one)
>
> -tgq
>
> "Trevor Quayle" <Tin### [at] hotmailcom> wrote in message
> news:3bd072ea$1@news.povray.org...
> > When POVRay uses AA, does it use the actual colours and relative
> brightness
> > or the clipped colour? (i.e., do pigment values > 1 have more influence
> than
> > those 1 or less)
> >
> > -tgq
> >
> >
> >
> >
>
>

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"Slime" wrote:
> it should clip the values first.

As far as I can see it does clip the values first. I don't know how Trevor
came to his conclusion.

Rune
--
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POV-Ray Users:   http://rsj.mobilixnet.dk/povrayusers/
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On 2001-10-19 20:03, Slime <noo### [at] hotmailcom> wrote:
>> (yes it does use the full value not the clipped one)
> 
> Does it? It would make more sense to use the clipped value, I think. What AA
> simulates is as though you had rendered the file at an infinite resolution
> and then scaled it down to a finite resolution.

I don't think so. It should simulate the effekt of a film or CCD with
finite resolution. Using the full value is more physically correct. 

As a rather extreme example of where this make a difference, consider
trying to render the night sky from physical data (size, distance and
brightness of the stars). Ignore for a moment that povray isn't well
suited to that task for numerical reasons, and concentrate only on the
antialiasing:

Stars are extremely bright objects but also extremely small because of

1000x1000 pixels, a bright star will have a diameter of about 1/5000
pixel and therefore cover less than 1/25E6 of its area. If the clipped
value is used, even with 16 bit output, the picture will always be
completely black. But in reality, we all know that we can see the stars.

	hp

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