[Radiance-general] advice for material modeling

[Lars O. Grobe]

Hi Dan,

as a general rule of thumb, you can modifiers to perturbate the surface 
(e.g. vary brightness, surface normals) as long as the average of the 
perturbation is one. In this case you would use your measured 
reflectance as a base material and apply some fancy structure-modifiers 
to it.

For the case where you want to perturbate the color, too, it will be 
more complicated. As far as I understood, you only have the average 
reflectance, but you do not know the local colors. You may try the same 
as above, ensuring that the average complies with your measured 
reflectance, and use colorpict or colorfunc to perturbate the color. But 
this may leas to strange effects.

Best would be calibrated photographs.

Cheers, Lars.
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