I believe fog is a combination of emission and absorption. In other words,
it's scattering media. (Scattering media is identical to a combination of
emission and absorption, except that it also interacts with light. The light
is what causes the emission. So if there's no light in a part of the
scattering media, it will only be absorption there.)

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

"Philippe Debar" <phd### [at] yahoofr> wrote in message
news:3BD### [at] yahoofr...
> I am trying to go a little further then 'dumb user' and understand the
> exact (mathematical) way colors interact with fog and media. Which led
> me to questions about filter and transmit.
>
> * fog works like transmit : it adds its color, which is a function of
> the distance between the camera and the object seen through the fog, to
> a fraction of this object color. The color vectors are added, something
> like this : fog_local_color(fog_settings,
> distance)+fog_local_transmit(fog_settings, distance)*object_local_color
>
> * absorption media works in a way similar to filter : it "absorbs
> frequencies". I believe the mechanics are rather different : the filter
> works by multiplying color vectors (is this correct ?) while media color
> is substracted (?).
>
> * emission media works the other way : the local media color is added to
> the seen-trough-media object (?)
>
> * scattering media is another beast altogether ;-)
>
>
> Is there a place I can find the formulas used for filter, transmit, fog
> and medias (other than source-code) ? (I mean the code for color
> interaction between seen-trough and seen, not the code used to determine
> local density or anything like that... just the way the colors affect
> one another to produce final color.)
>
> I do not know a way to produce a media that reproduce the behaviour of
> fog... is this possible ? (to benefit from localisation in an interior
> and density capabilities of media)
>
>
> TIA
>
>
> Povingly,
>
> Philippe
>

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