[Radiance-general] Re: falsecolor's isolux on observer's luminance.

[Greg Ward]

Hi Lucio,

It's probably easiest just to make the invisible areas zero in the  
falsecolor image, which you could do like so:

% vwrays -ff -vf ortho.vf -x XRES -y YRES -pa 0 \
	| rtrace -h -ff -op roadway.oct > roadpts.flt
% rcalc -if3 -of -e '$1=OX;$2=OY;$3=OZ;$4=$1-OX;$5=$2-OY;$6=$3-OZ'  
roadpts.flt \
	| rtrace -ff -opv -x XRES -y YRES roadway.oct \
	| rlam -if3 roadpts.flt -if6 - \
	| rcalc -if9 -of -e 's(x):x*x;OK=0.2-s($1-$4)-s($2-$5)-s($3-$6)' \
		-e '$1=if(OK,$7,0);$2=if(OK,$8,0);$3=if(OK,$9,0)' \
	| falsecolor -cl -s auto \
	| ra_tiff - roadway_lum.tif
% rm roadpts.flt

The usual caveats apply, as I haven't tried this.  If your world  
units are cm or something smaller, the 0.2 value might have to be  
increased for reliable behavior.

-Greg

> From: "loscotec\@libero\.it" <loscotec at libero.it>
> Date: February 9, 2008 2:39:54 AM PST
>
> Wow Greg, that's amazing !
>
> That solution is simple and powerfull at the same time. And Indeed  
> it helped me much in learning how to behave with Radiance's programs.
>
> THANK YOU
>
> But let me annoy you a little further. Going on thinking about this  
> problem, I realized that what I really need is something different.  
> I don't actually need ray to be traced from close to the point,  
> 'couse this point aren't actually seen from the observer.. Neither  
> I need ,as it was before, to have wrong informations. Then probably  
> the best option would be to mark the 'wrong' points to understand  
> them are not seen from the observer. A good way could probably be  
> to paint them with an unreal color (or luminance level if  
> postprocessed by falsecolor).
>
> The method could be to check if ray intersection points with  
> surfaces are different from the ones requested, and, in that case,  
> to paint that area with given values. This could probably be  
> achieved also building up some kind of mask image to combine later  
> with pcomb ... ?
>
> Well, I'm sure it is possible, and it is probably simpler than I  
> figure it out, but I have no idea on how to achieve it.
>
> Well, I'n neither in a hurge now of building such system, so don't  
> worry if you cannot answer.
>
> Lucio