[Radiance-general] computing illuminance across a grid

[Phillip Greenup]

Hi Rob,

Do you have rillum?  if you have rillum, it makes this process somewhat easier.

1. create an input file with a pile of measuring points and positions, 
similar to your 60 60 30 0 0 1.  cnt and rcalc can help in the creation of 
this file, but it can also be done in any text editor, or spreadsheet and 
exported as an ascii file.  use one line per measuring point.
2. rillum [rtrace options] octree < infile > outfile

the output file then contains a column of illuminances corresponding to the 
measuring points and orientations defined in the input file.  if you wish, 
you can then use lam to put the input and output files together in a table.

good luck!
Phil Greenup.

At 03:58 pm 22/05/02 -0400, you wrote:
>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