[Radiance-general] Radiance and irradiation

[Giovanni Betti]

Thanks for your quick reply Lars, of cousrse I meant Windows!!! ;)
So here I am into the Command Prompt but if I specify what you suggested
me pcomb fails and no output is created (more precisely: a 0 kb file is
created as output). The error I receive is about bad picture size... Any
clue about how I can fix that?
Thanks!
 
Giovanni 


-----Original Message-----
From: radiance-general-bounces at radiance-online.org
[mailto:radiance-general-bounces at radiance-online.org] On Behalf Of Lars
O. Grobe
Sent: 07 April 2009 12:11
To: Radiance general discussion
Subject: Re: [Radiance-general] Radiance and irradiation

Hi!

> having access to a Linux machine, I am forced to stick to pc.

I do not want to be picky, but you probably mean Windows, not PC here
;-)

> I understand radiance calculates irradiance and then uses a standard 
> conversion factor Kr=179 lumens/watt. Hence it should be possible to 
> use it for solar irradiation calculation as well as for light
analysis.
> 
> My question is, how can I display directly watts/m2 instead of lux?

Depends on what you mean by display. The most useful way would be
falsecolor images. As falsecolor by default multiplies pixel values by
179 to get from radiometric to photometric units, you must tell it to
use a multiplier of 1 instead of 179. Than, you most probably have to
set the scale in a way that you see the irradiances in your image. One
example, using a scale of 0-5000 and the multiplier 1 (to avoid the
conversion to lx) would be like this:

falsecolor -i input.hdr -m 1 -s 5000 -l "Watts/m2" > output.hdr

> As well, in order to perform irradiation analysis a sky generated 
> following the perez-all weather model would be more accurate than just

> using the standardCIE skies supported by gensky. I understand there is

> an application called gendaylit that does exectly this. From where can

> I download a windows version?

Sorry but I have no idea wether you can do that.

CU Lars.