[Bf-committers] BRDF conversion - Was Farsthary anouncement

Arne Schmitz arne.schmitz at gmx.net
Thu Feb 12 11:08:56 CET 2009

Am 10.02.2009 um 07:46 schrieb joe:

> The mathematical definition of a BRDF is simple enough, that it seems
> you could wrap specular and diffuse legacy shaders into a blackbox,
> with all the parameters stored internally, not visible to the outside
> world.  Sure, it'd suck quite a lot, but what I'm wondering is if
> that'd work better then trying to mathematically map legacy shaders to
> valid BRDF's.

The problem with many legacy materials / BRDFs is, that they are not  
true BRDFs. That is they violate some conditions of being a physically  
valid BRDF. For example the traditional Phong model is not energy  
conserving, i.e. it might create more reflected radiance, than  
incoming radiance is produced. With this in mind, I figure you /could/  
for example map a legacy BRDF to a 6-dimensional function defined on  
spherical harmonics, and  make a least squares approximation to a  
valid, modern BRDF that is physically sound. You will notice  
differences, but it would still be nice. Anyone want to write a paper  
about that? :) I think SIGGRAPH Asia deadline is coming up...



Dipl.-Inform. Arne Schmitz              Phone   +49 (0)241 80-21817
Computer Graphics Group                 Fax     +49 (0)241 80-22899
RWTH Aachen University                  http://www.rwth-graphics.de
Ahornstrasse 55, 52074 Aachen, Germany

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