[Radiance-general] Re: Again transmissivity for color filter/ glass

[Gregory J. Ward]

Hi Christian,

> Now i want to ad the color attributes of this filter somehow to  
> this cylinder:
> I think the best way to simulate this, is to use the 'trans'  
> material because the surface shouldn't be so shiny or polished like  
> the glass material.
> I made an Excel sheet to calculate the 'trans' parameters but it's  
> confusing.

Why is the filter material not shiny?  Does it have a rough texture  
that scatters light?  If it is solid and transmits light, then it  
also reflects light.  It might have a low index of refraction if it  
is a gel filter, similar to water with n=1.3, whose surface  
reflection is around 2%.  You can give the index of refraction to the  
glass type as a fourth argument.  (If you give a value of 1.0, there  
will be no reflection at all.)

Whether you end up using 'glass' or 'trans' as your material, be sure  
to leave a small gap between the surface you use for your filter and  
the surfaces you use for your cylinder.  Otherwise, the rays will see  
one or the other surface at random.

-Greg