[Radiance-general]Directional reflectance of glass

[Christian Humann]

Hello all,

I'm trying to simulate the occurrence of direct beam convergence; where 
sun hitting a concave, east facing, glass facade is redirected to form a 
"hot-spot" on the ground plane.  I have a photograph, and the time 
taken, of the building in question forming a hot spot as well as a 3D 
model. Using the "mirror" material type I can get an approximate 
facsimile, but not with the "glass" material. I've tried the glass using 
"mkillum" and setting -ar 0 but I still can't "fry" those ants. 

I'm under the impression that Radiance only considers the glass' 
reflected diffuse component, and not the direct (although I can see the 
sun's reflection in the glass)?  While close, I don't believe the 
"mirror" material will give the accuracy we're looking for due to the 
difference in effect the angle of incidence has on the amount of light 
redirected off the two materials.  Any thoughts, advice or observations 
would be greatly appreciated. Thanks.and regards.

Chris Humann
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