Distribute the brightness of the sun over a sky patch

Ale,

You should take a look at the "understanding rtcontrib" tutorial, by Axel
Jacobs. It is available on the radiance-online.org/learn/tutorials section.

You use rtcontrib (now you use rcontrib, which I understand is basically
the same, but faster) for calculating the contributions of each patch on
the scene. Genskyvec or gendaymtx, on their part, will generate the actual
vectors that represent the sky, including the sun unless you tell them
otherwise.

Bye

Germán

:

···

2014-02-25 5:27 GMT-03:00 Alejandro Pacheco Diéguez <[email protected]>

Hi,
I want to generate a Tregenza patched sky model that distributes the sun
contribution into one of this patches instead of considering it separately
from the sky dome. I know I am supposed to use rtcontrib but i am not sure
I understand how it works. Maybe someone can help me here.
Regards,
Ale

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Alejandro

You can look at the algorithm that Daysim uses to distribute the sun
between fixed positions (for example this presentation on slide 11:
http://www.gsd.harvard.edu/research/gsdsquare/Presentations/Radiance%20WS2009_DaysimInnovations_CReinhart.pdf).
Note that the developers found that a small subdivision of the sky is not
sufficient to model sunlight and shadows in sufficient detail. Therefore
the approach to use separate steps for sun and sky contributions in
coefficient based daylighting.

Regards,
Thomas

···

On Tue, Feb 25, 2014 at 3:27 AM, Alejandro Pacheco Diéguez < [email protected]> wrote:

Hi,
I want to generate a Tregenza patched sky model that distributes the sun
contribution into one of this patches instead of considering it separately
from the sky dome. I know I am supposed to use rtcontrib but i am not sure
I understand how it works. Maybe someone can help me here.
Regards,
Ale

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Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Hi Alejandro,

There's basic material on (pre-rtcontrib/neolithic) use of Radiance to predict daylight coefficients in 'Chapter 6' here:

http://climate-based-daylighting.com/doku.php?id=resources:thesis

Cheers
John

PS. I ditched the 'Aimed Rays' approach about 10 years ago and now use ~900 "light" sources (i.e. solid angles) per Tregenza patch. Probably overkill, but it's quick nonetheless. The 'aimed rays' approach only really worked for clear glazing, whereas the many light sources per patch will handle diffusing and redirecting materials described by cal files.

John Mardaljevic
Professor of Building Daylight Modelling
School of Civil & Building Engineering
Loughborough University
Loughborough
Leicestershire
LE11 3TU, UK

Tel: +44 1509 222630 (Direct)
Tel: +44 1509 228529 (Pam Allen, secretary)

[email protected]<mailto:[email protected]>

http://www.lboro.ac.uk/departments/civil-building/staff/mardaljevicjohn/

Personal daylighting website:
http://climate-based-daylighting.com<http://climate-based-daylighting.com/>