[Radiance-general] Surface normal and Rdot in mix functions

[Peter Apian-Bennewitz]

markku.norvasuo@vtt.fi wrote:

> 
> I have used .cal functions based on cos(theta) of the incoming (eye) ray.
> For this purpose, there is a special variable available, Rdot, which is the
> dot product of the eye ray and the surface normal and hence should be equal
> to cos(theta), if I have understood correctly. I have also supposed
> Radiance always flips the normal

... if I recall it right:
dielectric, interface, BRTDfunc, glow and mixfunc don't re-orient
surfaces and Rdot[-1:1]
colorfunc, brightfunc, transfunc (+ their ~data equivalents), trans,
plastic(2), metal(2), glass do flip surface normals and so Rdot[0:1] .

-Peter
-- 
 pab-opto, Freiburg, Germany, www.pab-opto.de