[Radiance-general] rewrite BRDF as .cal file for plasfunc

[Jack de Valpine]

I think that Dx, Dy, Dz correspond to the direction vector of the ray 
which is different than the direction vector of the view. So this may 
account for some of your funny results.

-Jack

Katja Doerschner wrote:

>Hi Roland,
>I just tried out your suggestion after getting funny results with the
>DxDyDz as view direction. Your 'hack' works perfectly!!!!! Thanks a lot.
>
>katja 
>
>----- Original Message -----
>From: Roland William Fleming <roland.fleming at tuebingen.mpg.de>
>Date: Monday, July 18, 2005 11:44 am
>Subject: Re: [Radiance-general] rewrite BRDF as .cal file for plasfunc
>
>  
>
>>Hi Katja ---
>>
>>Here's the hack I use.  Pass the viewpoint as arguments to the .cal 
>>function.  Then view direction is just:
>>
>>Vx = -(arg(1) - Px);
>>Vy = -(arg(2) - Py);
>>Vz = -(arg(3) - Pz);
>>
>>where Px, Py and Pz are the Radiance predefined variable names for 
>>the 
>>ray intersection points.
>>
>>Hope this helps,
>>Roland
>>
>>
>>On Jul 18, 2005, at 5:26 PM, Katja Doerschner wrote:
>>
>>    
>>
>>>I sent this message earlier - but I think it may have gotten 
>>>      
>>>
>>lost. I
>>    
>>
>>>apologize if you receive it twice!
>>>
>>>Hello,
>>>
>>>Has anyone an example of how to write a .cal function for plasfunc,
>>>for a given BRDF?
>>>Specifically, I am not sure which predefined variables correspond to
>>>the view direction vector.
>>>
>>>This is the BRDF I want to use in Radiance:
>>>V(i,j,n,a)=(1/PI)*(a/(a+(i dot n)(j dot n))
>>>:i is unit vector from the source direction, j is unit vector of 
>>>      
>>>
>>view> direction, n is surface normal, a some other parameter.
>>    
>>
>>>I know the Radiance-predefined variable names for the source 
>>>      
>>>
>>direction> (x,y,z) and surface normal (Nx,Ny,Nz), but I am not sure 
>>what to use
>>    
>>
>>>for the view direction.
>>>
>>>Can anyone help?
>>>Thank you!
>>>katja
>>>
>>>
>>>
>>>
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>>>Radiance-general mailing list
>>>Radiance-general at radiance-online.org
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>>>
>>>      
>>>
>>r o l a n d   f l e m i n g   p h d
>>r e s e a r c h   s c i e n t i s t
>>
>>m a x   p l a n c k   i n s t i t u t e   f o r   b i o l o g i c a 
>>l   
>>c y b e r n e t i c s
>>s p e m a n n s t r .   3 8
>>7 2 0 7 6    t u e b i n g e n
>>g e r m a n y
>>
>>t e l ::   [ + 4 9 ]   0 7 0 7 1   6 0 1 - 6 0 9
>>
>>
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>>Radiance-general mailing list
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>>http://www.radiance-online.org/mailman/listinfo/radiance-general
>>
>>    
>>
>
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>
>
>  
>

-- 
#	John E. de Valpine
#	president
#
#	visarc incorporated
#	http://www.visarc.com
#
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