Illuminance values contour lines on a working plane

According to what described on page 66 of the Radiance Cookbook, this procedure:

$ vwrays -x 400 -y 400 -vf horizontal.vf
| rcalc -e '$1=$1;$2=$2;$3=.4;$4=$4;$5=$5;$6=1
| rtrace -fac -w -I -ov vwrays -d -vf outside.vf \ -x 400 -y 400 room.oct > wp_illu.hdr

should give as a result the contour lines shown in the related picture. I assume I misinterpreted the text as I guess that the described procedure just gives the illuminance picture for the working plane defined by the .vf file.

To obtain the contour lines one should call the falsecolor function as usual so I would need to make two calculations, one with and one without the ‘-I’ option, right?

Thank you for your help.

Hi Danka,
you are correct – this only gives you the illuminance image. You’ll have to create the fc yourself.
There is no need to also run this without the -I option. Just run
falsecolor -ip wp_illu.hdr -other -options > wp_illu_fc.hdr
I hope this makes sense.