"Rafal 'Raf256' Maj" <raf### [at] raf256com> wrote
>
> "If you set fade_power in the interior of an object at 1000 or above, a
> realistic exponential attenuation function will be used"
>
> I didnt find more explanation in mannual - why this new forumla is more
> realistic, witch real-word materials have it, is this the best attenuation
> forumla - or is it still not perfect in compare to phisics rights ?
> How choose fade_power ? 1000 ? 1500 ? 10000 ?
> Should we always use new attenuation, or do some object look more
realistic
> with old formula ?

Hmmm... I don't know if that was supposed to make it into 3.5.

Anyway, if fade_power is >=1000, then the fade_power value itself is
ignored, and an exponential attenuation is applied.  Only fade_color and
fade_distance matter.  The exponential attenuation is almost identical to
constant attenuating media.

attenuation[] =
exp(-(1.0-Interior->Fade_Colour[])*Ray_Intersection->Depth/Interior->Fade_Di
stance);

Here it is as an ascii-art formula (fixed-width font preferred):


        / - Depth * (1.0 - Fade_Colour)\
       | ------------------------------ |
        \        Fade_Distance         /
att = e

This is applied separately to each color component (red, green, and blue).

-Nathan

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