[Radiance-general] Area lights breaking up?

[Rob Guglielmetti]

Ian Tester wrote:

>The problem appears to be with the roughness of the plastic. If it's set
>to 0, then reflections are shown. As soon as I increase it to as much 0.01,
>the plastic is no longer reflective and all we see is the specular
>highlights of the sub-divided area light pieces. Is this the intended
>behaviour? I remember spending quite some time fine-tuning these parameters
>to look just the way I wanted. Now nothing I can do will bring back the old
>appearance. The billiard balls should be glossy but not too smooth.
>
>
>The left ball has a roughness of 0.01, the one on the right is 0.
>
There is a paper (out there, somewhere) that describes the behavior of 
materials in Radiance.  In there, it says that for plastic with 
roughness greater than zero, where a reflected ray hits a light source, 
that ray is not used in the calculation because that would be 
double-counting.  I believe this is the cause of your two distinct 
renderings.  Perhaps someone else has some ideas as to how to get a 
rougher material that still renders a decent reflection of an area light?

P.S.
I had a look at your website Ian, any chance you might want to share 
those perl scripts you have that generated your sphereflake and water 
geometries?  I'm always interested in seeing geometry generators that 
people have created.

- Rob Guglielmetti
www.rumblestrip.org