[Radiance-general] Problems with polygonal light source

[Greg Ward]

Hi Tarik,

For a downward-directed light source, the ceiling is illuminated by 
interreflected light, which is approximated (to zeroeth order) with the 
-av setting in Radiance.  Better approximations may be obtained by 
setting -ab to 1 or greater.

-Greg

> From: Tarik Rahman <tarik.rahman at ed.ac.uk>
> Date: January 11, 2005 9:43:06 AM PST
>
> I'm trying to create a rectangular light positioned on the ceiling of 
> a room so
> I use
> void light bright
> 0
> 0
> 3  100  100  100
>
> bright polygon rectangular_light
> 0
> 0
> 12      2.25	0.05	2
> 	2.25	0.05	3
> 	2.75	0.05	3
> 	2.75	0.05	2
>
> but I have to position the light just below the ceiling (at height 0) 
> so that
> it's not obstructed by it and also the light only radiates from the 
> bottom of
> it's polygonal shape leaving the ceiling completely black. Can anyone 
> advise me
> what to do?
>
> Thanks
>
> Tarik