intermediate sky

radiance-general
1

Hi all!

Since it's the first time I write to this mailing list, I want to thank all,
and especially Greg Ward for coding Radiance!
Unfortunately I couldn't come to the 1st workshop, but I appreciated very much
that the papers are available online: fantastic!

My first question is about how Radiance models the intermediate sky.
I studied the code that generates the sky luminance distributions
(gensky.c + skygright.cal) and found that the overcast and clear skies
are modelled according to CIE 110-1994 Technical Report.
But the intermediate sky hasn't been coded according to the Nakamura, Oki et
al. sky function (that is the present standard, right?): is it related to
some previous standard?

Thank you!

···

--
Francesco Anselmo
[email protected]

2

From: Francesco Anselmo <[email protected]>

My first question is about how Radiance models the intermediate sky.
I studied the code that generates the sky luminance distributions
(gensky.c + skygright.cal) and found that the overcast and clear skies
are modelled according to CIE 110-1994 Technical Report.
But the intermediate sky hasn't been coded according to the Nakamura, Oki et
al. sky function (that is the present standard, right?): is it related to
some previous standard?

Hi Francesco,

I meant to reply to this message earlier, but I forgot. I also forgot where the intermediate sky model I used in gensky came from, but it wasn't my idea. I do recall that there were a few models competing at the time -- I wasn't aware that Nakamura, Oki et al was selected as the standard. Can you provide a reference?

At any rate, most people who are interested in more sophisticated sky simulations rely on the gendaylit program developed by Jean Brange while he was at the ISE in Fribourg. It may still be found on the Radiance website at:

  http://radsite.lbl.gov/radiance/pub/generators/

I don't know if there is a newer version, but if there is, someone should tell me so I can update the website copy.

-Greg

3

Hi all,
two minor corrections for the records:

At any rate, most people who are interested in more sophisticated sky
simulations rely on the gendaylit program developed by Jean Brange

Jean-Jacques Delaunay , last heard of to be at [email protected] in
spring 2000.

while he was at the ISE in Fribourg. It may still be found on the

Freiburg, - sorry for a sudden urge for patriosm with the two
Fr(e)ib(o)urgs.

Radiance website at:

        http://radsite.lbl.gov/radiance/pub/generators/

I don't know if there is a newer version, but if there is, someone
should tell me so I can update the website copy.

Not that I'm aware of a more recent version distributed from ISE.

-Peter

···

--
pab-opto, Freiburg, Germany, www.pab-opto.de

4

Hi!

I meant to reply to this message earlier, but I forgot.

No problem!

I also forgot
where the intermediate sky model I used in gensky came from, but it
wasn't my idea.

Ok, I'll try to find it by myself somehow ...

I do recall that there were a few models competing at
the time -- I wasn't aware that Nakamura, Oki et al was selected as the
standard. Can you provide a reference?

Of course! I can scan a copy of the CIE technical report and send it to
you ... just let me know ...

At any rate, most people who are interested in more sophisticated sky
simulations rely on the gendaylit program

I've used it sometimes, I know it uses the All-weather sky model, but I
was interested in understanding how gensky works, that's all ...

Thank you!

···

--
Francesco Anselmo
[email protected]

5

Sorry for the many errors in my e-mail on gensky. I was trying to beat my record for the most mistakes in the fewest words, which was already quite good. I should have known that gendaylit was by Msr. Delaunay, but at some point years ago, I got him confused with Msr. Brange. The confusion between Fribourg and Freiburg was more recent, and that was all in my fingers -- I just got too used to typing "Fribourg" for the workshop. I know the ISE is in Germany, not Switzerland. (It is in Germany, right?) Anyway, the german-speaking Swiss spell their Freiburg the same way on the other side of the river, so it's even more confusing....

That said, I would like a copy of the CIE intermediate sky standard. If Francesco could e-mail me an electronic or scanned copy, that would be great. Otherwise, my regular mail address is:

1200 Dartmouth St., #C
Albany, CA 94706
U.S.A.

(Not to be confused with Albany, New York.)
-Greg