[Radiance-general] BSDF material interaction with -ab

[Greg Ward]

Hello Marouane,

There is a separate "direct" calculation associated with all of the Radiance bsdf materials, which queries the reflectance function for the eye ray and source ray directions.  All bsdf materials include some notion of diffuse contributions, sometimes adding the non-source directional diffuse in with the truly Lambertian component.  Only the "BSDF" type sends additional rays in the non-source directions, keeping the Lambertian part separate.

I hope this helps.

-Greg

> From: Marouane.Boudhaim at ise.fraunhofer.de
> Date: April 20, 2018 1:57:44 AM PDT
> 
> Hello Radiance community, 
> 
> I was wondering in my reasearch how did -ab  parameter interact with bsdf based material. Specifically, how would an -ab 0 behave. Would it let me keep the direct portion of the calculation? If so what would be the direct portion, the transmitted ray that has the same direction as the incident one ? I'd guess such assumption wouldn't hold up very well in some cases. 
> 
> Sincerely, 
> Marouane
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