[Radiance-general] Modelling glass lamellas in Radiance.

[Gregory J. Ward]

Just a minor correction from what Thomas wrote...

> From: Thomas Bleicher <tbleicher at arcor.de>
> Date: January 6, 2007 10:43:22 AM PST
> ...
>> Here comes my dilemma:
>> The material type “glass”: in IESve the type does not include the  
>> refraction index which means that the only input is the  
>> transmissivity of the glass.
> 'glass' is a specialized form of dielectric with a preset refraction
> index of 1.52. It's refraction/reflection does not depend on the angle
> of incident light, though, which is what your looking for. It was  
> created
> to avoid the calculation of reflections between the two sides of a  
> glass
> pane and you have to convert your 'Transmittance' value to the  
> 'transmittivity'
> needed for the glass primitive definition if you go that way.
> [Note: that's what I understand about glass reading the 'usman.pdf'
>        document. Someone should correct me if I'm wrong.]

Actually, the "glass" primitive does correctly model reflection and  
transmittance changes as a function of angle, and it is possible to  
alter the index of refraction.  However, I don't think it's  
reasonable to set an index of refraction high enough to get a  
reflectance of 31% as Jacob specified.

>> The “trans” material type: same problem but at least I’m able to  
>> define the reflectance of the glazing.
> 'trans' materials don't have an index of refraction (not that I  
> know of).

Correct.  But you can apply a pattern such as "winxmit.cal" to  
incorporate the influence of incident angle.

-Greg