[Radiance-general] Radiance-general Digest, Vol 170, Issue 7

Tue Apr 24 10:30:31 PDT 2018

Hello Greg,

Thank you very much for your answer! I tried my very best to understand it 
but unfortunately I've hit a wall. 
I believe something about my understanding of BSDF material is lacking. 
genBSDF for example, produces klems BSDF which is a 145x145 matrix (for 
front/back,transmittance/reflectance) or tensor tree which a BSDF with 
variable resolution. 
I don't see how for example how "bsdf materials include some notion of 
diffuse contribution" separately from the rest of the calculation.  I 
failed to understand how the direct calculation is separate from the rest. 
I tried to check for documentation online about the BSDF material without 
much success.

Sincerely,
Marouane.

Von:    radiance-general-request at radiance-online.org
An:     radiance-general at radiance-online.org
Datum:  20.04.2018 21:04
Betreff:        Radiance-general Digest, Vol 170, Issue 7

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Today's Topics:

   1. BSDF material interaction with -ab
      (Marouane.Boudhaim at ise.fraunhofer.de)
   2. Re: BSDF material interaction with -ab (Greg Ward)

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Message: 1
Date: Fri, 20 Apr 2018 10:57:44 +0200
From: Marouane.Boudhaim at ise.fraunhofer.de
To: radiance-general at radiance-online.org
Subject: [Radiance-general] BSDF material interaction with -ab
Message-ID:
 <OF3363C61A.AAB47487-ONC1258275.0030B6DC-C1258275.00313B0E at ise.fhg.de>
Content-Type: text/plain; charset="us-ascii"

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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Message: 2
Date: Fri, 20 Apr 2018 07:15:09 -0700
From: Greg Ward <gregoryjward at gmail.com>
To: Radiance general discussion <radiance-general at radiance-online.org>
Subject: Re: [Radiance-general] BSDF material interaction with -ab
Message-ID: <194523BB-417B-4240-A6D6-E5E59AE7422E at lmi.net>
Content-Type: text/plain; charset="us-ascii"

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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