Demostration of rtcontrib in two stages.  The first computes
contributions as a function of angle from a window (divided into
three sections) and three skylights connected to a light pipe.
The second stage computes the incidence of sky illumination on these 
portholes, and the results are combined.  There are two main scripts,
run like so:

runrtcont.csh
runsums.csh

The first handles the two main stages, whose results are put into
src_cont/ and src_dc/ respectively.  The second script combines
the results into daylight coefficient pictures in the dc_cont/
folder.  A final script combines these into a result for a particular
date and time, e.g.:

sumpicture.csh 5 10 14:00PDT -g .12 > sunny5_10_14.pic
