[Radiance-general] Beware, indeed!

[Greg Ward]

Thanks to Raphael for pointing out that rlux is different from rillum -- 
I was mistaken in thinking them the same.  I really need to think more 
carefully before I type, and especially before I press "send!"  I 
realized after I'd sent that message that I had made another mistake, as 
the following is the correct way to execute rad to create an options 
file without running any renderings:

% rad -n -s scene.rif OPTFILE=render.opt

Without the -n option (as I had put in the last message), rad will run 
whatever renderings are indicated in the scene.rif file, which was not 
the point.  The -s option simply prevents it from echoing the commands 
it _would_ have executed, which you probably don't want to see...

There are a number of other fun ways to execute rad.  The following 
command will fill in ambient values for all the views in the scene.rif 
file at once (provided the AMBFILE variable is set):

% rad -v 0 scene.rif OPTFILE=render.opt
% rad -n -s -V scene.rif | rpict @render.opt -S 1 -x 64 -y 64 
scene.oct > /dev/null

The -v 0 option causes rad to generate the octree without rendering any 
views.  The -V option causes rad to print out all the views for this 
scene in the standard "VIEW=" specification that rpict accepts for 
animated sequences.  These views are then rendered by rpict at very low 
resolution and discarded, filling in the ambient file as a side-effect.

I used a trick like this in the "compamb" script to compute a good -av 
setting for a particular scene.  (See the man page for compamb, which 
comes with 3.4.)

I hope the above is correct, because I'm pressing "send," now!

-Greg