can the sun material identifier "solar" be specified in rcontrib?

Dear list,

Following Axel Jacobs' Rtcontrib tutorial (up to pp.19 so far), I used a
sky created by gendaylit rather than an overcast/uniform sky used in the
tutorial.

The hdr image i got by combining the 145 sky patch hdr images shows a dark
spot around the sun position. I assume this might be because only the "-m
sky_glow" argument is specified in rcontrib, thus the image generated
doesn't include the contribution from the sun spot.

However, when I include an additional "-m solar" argument (the material
identifier for the sun geometry) to the rcontrib command I only got strange
sky patch images.

May I ask why this approach is not correct? and how to visualize the
contribution from the sun spot?

Thanks!
Ji

The shell script (without sun material identifier):

ยทยทยท

##############################
# create a sky description using gendaylit

gendaylit 1 1 9 -a 1.37 -o -103.98 -m -120 -W 70.0 130.0 -O 1 >
./skies/sky_gendaylit.rad

# copy all lines in the original sky.rad and past in the newly generated
sky_gendaylit.rad above

oconv ./materials/testroom.mat ./objects/testroom.rad
./skies/sky_gendaylit.rad > testroom_gendaylit.oct

# viz the contribution from each of the 145 patches in the gendaylit sky
from the fisheye viewpoint

DIMS=600

vw="-x $DIMS -y $DIMS -vf ./views/sky.vf"

vwrays -ff $vw | rcontrib -bn 146 @./rtc.opt -ffc \
`vwrays -d $vw` -V+ -f tregenza.cal -b tbin \
-o ./images/patches_gendaylit_skyview/p%03d.hdr \
-m sky_glow ./testroom_gendaylit.oct

# use Andy McNeil's approach to merge the 145 hdr images

pcomb $(for i in {001..145}; do \
echo "./images/patches_gendaylit_skyview/p$(printf "%03d" $i).hdr"; done) \

./images/sky_pcomb_gendaylit_skyview.hdr

falsecolor -ip ./images/sky_pcomb_gendaylit_skyview.hdr -s 10000 -l cd/m2
-n 10 \

./images/sky_pcomb_gendaylit_skyview_fc.hdr

##############################

The shell script of rcontrib with the sun material identifier included:
##############################
vwrays -ff $vw | rcontrib -bn 146 @./rtc.opt -ffc \
`vwrays -d $vw` -V+ -f tregenza.cal -b tbin \
-o ./images/patches_gendaylit_backview_withSun/p%03d.hdr \
-m sky_glow -m solar ./testroom_gendaylit.oct
##############################