Does anyone know how fog works?

Yesterday I was working in my Hiroshima image and I thought "It would be
possible using ground fog, to make an spherical fog writing

up x*y*z

or something similar?"
Well, the idea is that it happens something I dont understand but it doesnt
sets any error. So probably something can be done.

And why I want to do something like this? because in some cases it can look
like the interior propertie but renders much more faster. Does anyone know
something about this?

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kike wrote:
> Does anyone know how fog works?
Yes

> Yesterday I was working in my Hiroshima image and I thought "It would be
> possible using ground fog, to make an spherical fog writing
> 
> up x*y*z

Not that way, obviously P))

> or something similar?"
> Well, the idea is that it happens something I dont understand but it doesnt
> sets any error. So probably something can be done.
> 
> And why I want to do something like this? because in some cases it can look
> like the interior propertie but renders much more faster. Does anyone know
> something about this?

Right off the top my my head, I can think of two faster alternatives to 
media:

MegaPOV's glow. It's fast.

A sphere like this (needs a background brighter than rgb<0,0,0>:

sphere{
  0,1
  pigment{rgbt}
  interior{fade_power 2 fade_distance .2 fade_color<10,10,3>
}

~Sam

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kike nous apporta ses lumieres en ce 11-04-2007 09:33:
> Does anyone know how fog works?

> Yesterday I was working in my Hiroshima image and I thought "It would be
> possible using ground fog, to make an spherical fog writing

> up x*y*z

> or something similar?"
> Well, the idea is that it happens something I dont understand but it doesnt
> sets any error. So probably something can be done.

> And why I want to do something like this? because in some cases it can look
> like the interior propertie but renders much more faster. Does anyone know
> something about this?


Ground fog is relative to a plane and the "up" vector is the normal of that 
plane. Anything below the fog_offset have a constent density, and that density 
diminishes according to that formula: 1/(1 + (y - Fog_Offset) / Fog_Alt) ^2 .
Fog is not contained and don't interact with light (the main reason why it's 
faster).
Translation don't affect fog. You can rotate the fog or the up vector.

-- 
Alain
-------------------------------------------------
Everything can be filed under "miscellaneous".

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> Ground fog is relative to a plane and the "up" vector is the normal of that
> plane. Anything below the fog_offset have a constent density, and that density
> diminishes according to that formula: 1/(1 + (y - Fog_Offset) / Fog_Alt) ^2 .
> Fog is not contained and don't interact with light (the main reason why it's
> faster).
> Translation don't affect fog. You can rotate the fog or the up vector.
>
> --
> Alain

Ok, thanks. I knew moreless all that you said. The thing I didnt knew was
the part of the interaccion with light and the way the fog was linked to
the plane.

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