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

[Lars O. Grobe]

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.