[Radiance-general] Getting numerical errors while using secondary light sources...

[webmaster at audice.com]

Dear friends,

I'm trying to make use of advantages of the "secondary" light sources
to speed up the indoor irradiance calculations.

In the test below we have compared a daylight factors in a room,
calculated along the central depth axis of the floor.

The room parameters are:
3.2 meters - width,
5.6 meters - depth,
2.5 meters - height.

The window is 1.92 meters width and 1.5 meters height 0.8 meters
altitude (above the floor).
The room is located in the building having external obstruction
(another building) on the opposite side of the street.

The uniform sky model was used.

I run Radiance (3.7.2 and 3.7.3) with different parameters and here
are the most valuable of them:
http://www.audice.com/radiance/Graphs_3.png

Where:

"Radiance Illum 1" and "Radiance Illum 2" - the scene was divided into
an outdoor and indoor parts. At the first pass the distribution of light
from the window was calculated in the outdoor scene. At the second
pass the daylight factors were calculated in the indoor scene.

For window material I used:

void illum window_mat
0
0
3                  0                  0                  0

I didn't use "glass" material, because I needed rather empty opening
than the glass.

"Radiance Illum 1"
Parameters I used for mkillum:
-ab 4 -aa .2 -ar 128 -ad 512 -as 256 -dp 256 -ds .15 -lr 8

Comment in scene .rad file:
#@mkillum i=window_mat d=64 s=24 m=wind_illum f=./dist/window c=n b=0

Parameters I used for rtrace:
-ab 8 -aa .1 -ar 128 -ad 512 -as 256 -dp 256 -ds .15 -lr 8

--
"Radiance Illum 2"
Parameters I used for mkillum:
-ab 8 -aa .1 -ar 128 -ad 512 -as 256 -dp 256 -ds .15 -lr 8

Comment in scene .rad file:
#@mkillum i=window_mat d=256 s=128 m=wind_illum f=./dist/window c=n b=0

Parameters I used for rtrace:
-ab 8 -aa .1 -ar 128 -ad 512 -as 256 -dp 256 -ds .15 -lr 8

--
"Radiance Standard" - no illum surfaces were used. The model was not
divided into indoor / outdoor parts so the interreflection calculation
was used to compute the contribution from the window.

rtrace parameters used:
-ab 8 -aa .032 -ar 512 -ad 2048 -as 1024 -dt .05 -dr 8 -dp 2048 -ds .1
-dc .6 -lr 8

--
What causes more than 6% error for "Radiance Illum 1" and "Radiance
Illum 2" in the "pink" zone? Is there any way to get more accurate
results using secondary light sources?

-- 
Best Regards,
Ilya A. Zimnovich
mailto:webmaster at audice.com