[Radiance-general] Daylight factors

[Thomas Bleicher]

On Thu, Jun 18, 2009 at 6:32 PM, Chris Yates <Chris at zed-uk.com> wrote:

>  Dear all
>
> I'm looking to replicate some of the functionality of IES Radiance in the
> full version of Radiance. This is so we will not be as restricted by
> licensing ;)
>
> The feature I'm interested in is the illuminance calc on the working plane
> of a space. This is frequently used to feed in to such things as BREEAM or
> LEED credits.
>

Please be prepared to defend your procedures if someone comes along
and has some doubts about the result. If you use a package that has the
official blessings (like IES) you can just push a button and point to the
certificate to make your results credible.

If you roll your own you have to know what's going on and how to validate
your results.


> In IES Radiance, working on a multi roomed model,  I would:
>
>    1. Set up some basics, i.e. CIE overcast, materials, image quality
>    2. Select analysis type "illuminance - working plane" (usually 0.85
>    metres above floor level)
>     3. Select a space
>    4. Simulate!
>    5. Repeat 3 until all the spaces I'm interested in are simulated.
>
> [...]

If I were to export a 3rd party CAD model (via, say su2rad) consisting of N
number of rooms, are there alternatives to the simple IES approach?

Since you asked:

In su2rad you would

1) check that your model is suitable for daylight simulations and
patch the geometry where necessary

2) define polygons where you want your working planes. If you want
more than one you also have to define groups to keep them apart.

3) Export - this will create files with calc points suitable for rtrace
input

4a) manually feed rtrace with these files and pipe it through rcalc to get
lux or df
4b) I might have already bundled a script to do it for you ...

5) use any form of spreadsheet, data visualizer or simple command
line tool to calculate your averages or plots.

In the future it may be possible to create an image from the polygons
via John M.s stencil method and visualise rtrace results in su2rad.
But we're not there yet.

WRT the other points mentioned: You can select an area in ximage
and print out the average as well as highlight max (and min?) values.
But I think you would be better off with defining a mask image and
use a composite. It's a precise and repeatable process as oposed
to manual input of pixel coords.

The tutorial materials should be on the RwR CD. I can have a look
when I'm back home next week.

Cheers,
Thomas


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