[Radiance-general] Radiance trans widget for Mac OS X

[David Geisler-Moroder]

Hi Lars,

without testing it I would say your trans specification exactly does what
you want (100% diffuse tranmission).  However, this is a border case where
the formulae for trans as in RwR on page 325/326 are not defined (dividing
0/0)...

Cheers,
David

2013/1/17 Lars O. Grobe <grobe at gmx.net>

> Hi all,
>
> I know that questions regarding the trans model tend to be either
> repetitive or lead to never-ending threads, however here is one more in the
> series.
>
> I wanted to model a translucent surface, where I know really nothing about
> reflection. My idea was to keep Rd and Rs set to zero and only define the
> transmission. A simple example would be a surface with perfect lambertian
> transmission (Td=1, Ts=0) and no reflection at all (ok, hard to produce
> such a material, but I had reasons to separate transmission from reflection
> information). According to my understanding that would be:
>
> void trans puretransmission
> 0
> 0
> 7       1       1       1
>         0       0
>         1       0
>
> However, being lazy, I thought this might be a good time to try the widget
> for cross-checking. Which made me realize that Cr, Cb, Cg are not asked
> for. Instead, I seam to need a value > 0 for Rd, which means I can never
> achieve the above definition.
>
> Am I just doing it wrong? Did this problem never arise because noone else
> wanted such a strange trans model? Or - which would give me a headache - is
> my understanding of Cr, Cg, Cb wrong? I always understood
> A1-A3=1-absorption(r,g,b).
>
> Thank you, cheers, Lars.
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