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Hmm... how come when I put two grey colored fogs in my scene, near the
horizon i get a pure white color? It seems to be adding the fog colors
together... I expected something more like an *average* of the grey colors.
Here's the fog I'm using...
fog {
distance 40
rgb <.7,.7,.9>
fog_type 2
fog_offset 3.5
fog_alt 1.5
turbulence .6
octaves 8
omega .6
lambda 3
turb_depth .6
}
fog {
distance 40
rgb <.9,.9,1>*.3
fog_type 2
fog_offset 60
fog_alt 10
}
How can I keep it from getting white near the horizon?
- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]
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Hmm, setting the second fog to black (rgb 0) and giving it a distance of
1e-10 still keeps the first fog visible. Is this really the intended
behavior?
- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]
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In article <3c44d8c2$1@news.povray.org>, "Slime" <noo### [at] hotmail com>
wrote:
> Hmm, setting the second fog to black (rgb 0) and giving it a distance of
> 1e-10 still keeps the first fog visible. Is this really the intended
> behavior?
If you want accurate results, use media instead of fog. Fog is really a
quick-n-dirty cheat, it only works for certain situations, though it's a
lot faster.
--
--
Christopher James Huff <chr### [at] maccom>
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> If you want accurate results, use media instead of fog. Fog is really a
> quick-n-dirty cheat, it only works for certain situations, though it's a
> lot faster.
Yup, yup... I've resorted to media... although I'm having a tough time
getting the emission and absorption to work well together (as usual). Should
they be emitting and absorbing the same color, or opposite colors, or what?
It seems that if there's any absorption at all, then things turn black on
the horizon...
(note: I don't care about light interaction.)
- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]
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On Tue, 15 Jan 2002 23:37:28 -0500, "Slime" <noo### [at] hotmailcom>
wrote:
>Yup, yup... I've resorted to media... although I'm having a tough time
>getting the emission and absorption to work well together (as usual). Should
>they be emitting and absorbing the same color, or opposite colors, or what?
Depends on the effect you're trying to achieve. In general, I wouldn't
use emission in this case because that's physically incorrect. Your
best bet is a thin scattering media or semi-transparent fog.
Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG e-mail : pet### [at] tagpovrayorg
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> Depends on the effect you're trying to achieve. In general, I wouldn't
> use emission in this case because that's physically incorrect. Your
> best bet is a thin scattering media or semi-transparent fog.
Well, I was using emission to simulate scattered light without using
scattering, since scattering would require many, many samples (especially in
this scene) to keep from being grainy. Since I don't care about the
direction of the light or shadows, I figured emission would suffice.
It seems, however, that even if I have emission 100 and absorption .00001,
as the distance from the camera approaches infinity, the fog color becomes
black (absorption wins over emission). Could someone explain to me why this
is the case? I assume it's physically correct (even though it doesn't happen
with a simple fog declaration), but I'd still like to know why it happens.
If real fog consists only of absorption, then how come it doesn't become
black on the horizon? Or does it? (I live in a wooded area, so I can't tell
=)
- Slime
[ http://www.slimeland.com/ ]
[ http://www.slimeland.com/images/ ]
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"Slime" <noo### [at] hotmailcom> wrote in message
news:3c45a873$1@news.povray.org...
> If real fog consists only of absorption, then how come it doesn't become
> black on the horizon? Or does it? (I live in a wooded area, so I can't tell
> =)
Off-hand, I'd say the answer is because it doesn't consist only of absorption,
if any. Scattering via reflection and difraction is a (RL) fogs main attribute.
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"Tom Melly" <tom### [at] tomandlucouk> wrote in message
news:3c45a9af$1@news.povray.org...
> "Slime" <noo### [at] hotmailcom> wrote in message
> news:3c45a873$1@news.povray.org...
> > If real fog consists only of absorption, then how come it doesn't become
> > black on the horizon? Or does it? (I live in a wooded area, so I can't
tell
> > =)
>
> Off-hand, I'd say the answer is because it doesn't consist only of
absorption,
> if any. Scattering via reflection and difraction is a (RL) fogs main
attribute.
Yes, at some distance and thickness of fog you never see through it and only
see the fog itself at some point. If in RL it only absorbed light it would
go black I guess, if only emitted it would go white.
Anyway, have you tried fade_distance for the light_source? Together with
media_attenuation in that light to fade out the media might work, and try
leaving out the absorption part.
bob h
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