[Radiance-general] irradiance vs. radiance / luminance vs. illuminance

[Greg Ward]

> vwrays [view options] -ff -x xres -y yres -pa 0 | rtrace -h -ff - 
> opN octree | rtrace -ffc -I -x xres -y yres > irrad.pic

Obviously, I forgot the octree on the second rtrace command.  Also,  
you need to specify the appropriate x and y resolutions for square  
pixels, or use the more complicated procedure with the vwrays -d  
option specified on the man page:

	http://radsite.lbl.gov/radiance/man_html/vwrays.1.html

-Greg