[Radiance-general] computing illuminance across a grid

[Georg Mischler]

Rob Guglielmetti wrote:

> cnt 15 30 | rcalc -e
> $1=(144-6)/(15-1)*$1;$2=(168-6)/(30-1);$3=30' \
> -e '$4=0;$5=0;$6=1' | rtrace -I -h [options] octree \
>   | rcalc -e '$1=179*(.265*$1+.670*$2+.065*$3)' >
> output.dat
>
> (note: the first two lines above are on one line in the
> command file.  Damn emailer.)
>
> This should place a grid of "light meters" facing up, 2'6"
> off the floor, right?  Why is my scene illuminance reading
> zero??  It's a daylit space!  When I load a pic into ximage
> and pick a point & press return, I get radiance values of
> .298, .428, on the floor.  Hmmm...


That's what you get for using those weird nonstandad units... ;)
I suspect that your points are located inside some wall,
since they all have the same y-value of 5.5862069.

You migh want to check the output of the first two stages
of the pipe sequence for a sanity check:

 cnt 15 30 | rcalc -e '$1=(144-6)/(15-1)*$1;$2=(168-6)/(30-1);$3=30' \
  -e '$4=0;$5=0;$6=1'

(You also had a quote character missing at the start of the first
expression, but that's probably a copying error in the e-mail)


-schorsch


-- 
Georg Mischler  --  simulations developer  --  schorsch at schorsch.com
+schorsch.com+  --  lighting design tools  --  http://www.schorsch.com/