[Radiance-general] Calculating diffuse component in a BRTDfunc

[atelier iebele abel]

--- (previous message was messed up a bit, hope this times it is better) ---

Hi all,

I am writing a BRTD material which I want to use to change the diffuse component of a surface, related to a certain direction and the surface 
normal. Radiance reports: "error bad arguments for BRTDfunc

I get the impression that the rfdif, gfdif, bfdif, rbdif, gbdif and bbdif are not variables ?
If these are not variables, how can I change/calculate/define the diffuse component in a BRTDfunc?
See the bold lines of the example in my cal file.

I appreciate any suggestions !

Iebele

<--- snip  ---->

{

   directional.cal

   arg10 red diffuse
   arg11 green diffuse
   arg12 blue diffuse
   arg13 direction x 
   arg14 direction y
   arg15 direction z

}

{ RGB values for the reflection  }

	valr  = arg(10);
	valg  = arg(11);
	valb  = arg(12);
	xdir = arg(13);
	ydir = arg(14);
	zdir = arg(15);
 

{ dot product direction and normal }
	DdN = (xdir*Nx)+(ydir*Ny)+(zdir*Nz); 

{ always return a positive value }
	multi = if(DdN, DdN, -DdN) ;

	*reflr* = CrP + (multi*valr)  ;
	*reflg* = CgP + (multi*valg)  ;
	*reflb* = CbP + (multi*valb)  ;

{

   	example usage: 

       	void BRTDfunc LAYER114
	10
	0 0 0                          / reflection
	0 0 0                          / specular
	0 0 0          
       	directional.cal
	0
	15
	*reflr reflg reflb*              / diffuse front
	*reflr reflg reflb*              / diffuse back
	0 0 0                          / trans
	0.8 0.7 0.6                    / color of surface
	0.57735 0.57735 0.57735        / vector defining bright side of surface

}

 

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