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:[email protected]