Radiance and lightshelves

Hi, I'm trying to investigate the effectiveness of a lightshelf using a
Radiance model. I'm finding that either the lightshelf is totally
ineffective or there's a problem with my model or my use of Radiance. Has
anyone done anything similar and is willing to give me some advice?

Thanks,

Nick

Nick,

Need a little bit more information: is the shelf specular and are you modelling skies with sun? If yes to both, are you modelling the shelf as material "mirror" and have you set the parameters for the "virtual light source" calculation accordingly? See section 11.3 of the Radiance book and have a look at the "virtual" office example in the "obj" directory of the Radiance release.

-John

2006 Radiance Workshop:
http://www.iesd.dmu.ac.uk/~jm/radiance2006work.html

···

-----------------------------------------------
Dr. John Mardaljevic
Senior Research Fellow
Institute of Energy and Sustainable Development
De Montfort University
The Gateway
Leicester
LE1 9BH, UK
+44 (0) 116 257 7972
+44 (0) 116 257 7981 (fax)

[email protected]
http://www.iesd.dmu.ac.uk/~jm

I used a semi-specular 90% reflective plastic material for the shelf under
both cloudy and intermediate sunny skies. I guess this explains why no
direct sunlight was being reflected. I'll read up on the virtual light
source calculation and try using a mirror material later. I'm still not
sure why I saw virtually no improvement in daylight distribution, even
without the direct reflection shouldn't there be some bouncing of diffuse
light deeper into the space. I used quite a high ceiling reflectance and I
think I used sufficient ambient parameters, number of bounces etc.

The test room was based on the one in chapter 6, with a 500mm clerestory
window, 500mm internal projection and 750mm external projection. I used
skies for spring, summer and winter at midday, latitude 51 degrees north: a
CIE cloudy sky, and four intermediate sunny skies rotated to give N S E W
orientations.

Nick

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-----Original Message-----
From: John Mardaljevic [mailto:[email protected]]
Sent: 20 June 2006 11:51
To: [email protected]
Subject: [Radiance-general] Radiance and lightshelves

Nick,

Need a little bit more information: is the shelf specular
and are you modelling skies with sun? If yes to both, are
you modelling the shelf as material "mirror" and have you
set the parameters for the "virtual light source"
calculation accordingly? See section 11.3 of the Radiance
book and have a look at the "virtual" office example in
the "obj" directory of the Radiance release.