[Radiance-general] mkillum -ab 0 question

[Marija Velickovic]

Hi,


I'm running some daylight calculations and experimenting with mkillum.
I'm interested which light components does mkillum takes into account as
input.

I've found in RWR book on page 380 nice diagrams, but no info what is taken
into account when -ab 0 is used.

What I've understood by now:
mkillum -ab any_value:
l- option in geometry file - direct light from light sources (eg. sun) is
skipped from mkillum calculation and used later in rtrace/rpict directly.
Output geometry is made of 'illum' material
l+ option in geometry file - direct light from light sources is taken as
input and included in output light distribution. Output geometry is made of
'light' material

mkillum -ab 0:
*-which sky/sun/reflected components are taken as input for mkillum?*

mkillum -ab 1:
-direct light from sky is included
-indirect solar component (once reflected from ground or some other object)

mkillum -av 0 0 0:
-what does this give us (I know that -av should be 'ground ambient level'
from gensky?

####
To explain why do I need such strange mkillum parameters

My idea is to get light patch, coming from the sun and reflected from
specular deflector surface into the room, but to exclude all other
influences  - direct light coming from sky or sun, or reflected light from
outside/inside surfaces.
I modeled deflector as mirror with alternative metal material with
appropriate reflectance/specularity.

*I want to get completely black image with reflected light patch only, so I
can sum images from various time moments during day/year and show light
patch moving for some period of time.*

To get image with specularly reflected light only:
1. I defined sky with sun only (no diffuse sky or ground sources)
2. Calculated mkillum -ab 0 -av 0 0 0 (l+ option) for my deflector surface
3. Used mkillum output in new octree as only light source (removed sun
definition)
4. Calculated image with rpict -ab 0 -av 0 0 0
Problem is that beside direct light patch inside  the test room, I still
get some light on surfaces above/below my deflector surface.

Even when I repeat calculation for sun behind my surface (so no direct
light on surface), my output from mkillum has some small radiance, and I
get some luminance on surfaces below/above deflector.

Any ideas are welcome?

I hope I managed to explain what I want, and which method I try to use to
get results (unsuccessfully for now :( )

Thanks in advance,
Marija
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.radiance-online.org/pipermail/radiance-general/attachments/20111214/068b13d8/attachment.html>