[Radiance-general] computing illuminance across a grid

[Rob Guglielmetti]

Me again.  I have a couple of test scenes I'm 
experimenting with, and I'd now like to use rtrace et. al. 
to automate the extraction of illuminance levels to a file.  

>From a Radiance digest:
> As an example of producing illuminance values at regularly
> spaced points on a 4x5 workplane, you might use the
> following command:
> 
>  % cnt 3 4 | rcalc -e
>  '$1=$1+.5;$2=$2+.5;$3=1;$4=0;$5=0;$6=1' \
>   | rtrace -h -I [options] octree \
>   | rcalc -e '$1=179*(.3*$1+.59*$2+.11*$3)' > outfile

Could you decipher this a little bit?  I don't see where you 
feed it the 4x5 grid.  Also, looking at the manpage, it 
looks like rtrace with the -I switch takes the input origin & 
direction and interprets it as "measurement point and 
orientation".

I tried something like:
rtrace -h -I 60 60 30 0 0 1 scene.oct 

I thought this would give me the irradiance at a point 60" 
over(+x), 60" up (+y), and 30" off the floor (+z), whth the 
"light meter" facing up along the z axis.  But this gave me 
an error at the command line.  WHat is the proper syntax? 
 I was hoping to fill a text file with measurement points 
and feed it to rtrace, and use something like your script 
above to produce a table of measurement points and 
corresponding illuminance values...

         ====================
 Rob Guglielmetti <rpg777@earthlink.net>
    http://home.earthlink.net/~rpg777