Warp wrote:

> Micha Riser <mri### [at] gmxnet> wrote:
>> but what is the meaning if both are?
> 
>   This is what I have wondered as well.

one way I could think of filter is that it is like a thinn, strong layer of 
scattering media behind the surface.. but I have no idea if the POV 
developper had this in mind or this is consitient with POV (probably not)

following the media approach I came to following:

The scattering part would be (approx.): f*(o*p)*dl
(where dl is something like the length of the media.)

The part of light shining through the media layer: 
 exp(-f*p*dl) * o 
which can be approximated using exp(x) = 1+x to:
 (1-f*p*dl)*o

setting dl to 1 and summing up gives:
 f*(o*p) + (1-f*p)*o

Now this shines only through as much as the transparency of the surface is, 
so the whole is multiplied by t. Including the "normal" lighting this 
gives:
 (1-t)*l + t*o*( f*p + (1-f*p) )

Any comments?

- Micha


-- 
POV-Ray Objects Collection: http://objects.povworld.org

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