POV-Ray : Newsgroups : povray.documentation.inbuilt : Possible error in 3.4.7.9 Server Time: 23 Oct 2019 03:07:26 GMT
  Possible error in 3.4.7.9 (Message 1 to 2 of 2)  
From: Bent
Subject: Possible error in 3.4.7.9
Date: 1 Jun 2005 19:55:00
Message: <web.429e1201ddf9f3ea18702db0@news.povray.org>
I think there's a typo in 3.4.7.9:
You should note two important facts: First, for Fade_Distance larger than
one the light intensity at distances smaller than Fade_Distance actually
increases. This is necessary to get the light source color if the distance
traveled equals the Fade_Distance. Second, only light coming directly from
light sources is attenuated. Reflected or refracted light is not attenuated
by distance.

The very first Fade_Distance should be Fade_Power, I believe.  Let me know
if I'm incorrect, but it really doesn't make sense as is.

Bent


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From: Jim
Subject: Re: Possible error in 3.4.7.9
Date: 20 Sep 2007 23:40:00
Message: <web.46f302b3f74215c291227f400@news.povray.org>
"Bent" <ben### [at] gmailcom> wrote:
> I think there's a typo in 3.4.7.9:
> You should note two important facts: First, for Fade_Distance larger than
> one the light intensity at distances smaller than Fade_Distance actually
> increases. This is necessary to get the light source color if the distance
> traveled equals the Fade_Distance. Second, only light coming directly from
> light sources is attenuated. Reflected or refracted light is not attenuated
> by distance.
>
> The very first Fade_Distance should be Fade_Power, I believe.  Let me know
> if I'm incorrect, but it really doesn't make sense as is.
>
> Bent

The docs sound OK to me. According to my (probably somewhat limited)
understanding, that section means:

"If you set the Fade_Distance to something larger than one, the illumination
at distances less than that will increase."

Fade_Distance is sort of where the "sample" point is for determining how
bright a light is. If you sample at a given distance, the intensity will
already have decreased. Often in the non-POV world you'll see brightness
indicated as "x units, at 1 meter" - this is basically the same thing.


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