Radiance and irradiation

Hi All,

I am a keen Radiance user since one year now but unfortunatly, not
having access to a Linux machine, I am forced to stick to pc. This is
under a number of aspect quite convenient because being an architect,
all of the other software I use is pc-based and I am totally unnfamiliar
with the linux os. I hope you can help me bearing in mind my type of use
of the software.
I have a couple of questions:

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?

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?

Thanks for your help,

Giovanni Betti

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 :wink:

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.

Thanks for your quick reply Lars, of cousrse I meant Windows!!! :wink:
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: [email protected]
[mailto:[email protected]] 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
:wink:

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.

Hi!

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?

The same command works here. Most probably something is wrong with your Radiance installation, the most common origin of all trouble are PATH and RAYPATH settings not pointing to the right directories. But here we hit a point that I cannot really help you - I have zero experience with Radiance on Windows, and usually it is guaranteed 100% more pain for doing the same. Can you check your installation?

CU Lars.

Sounds quite different... I can't even find those files in my radiance
installation!!
Thanks anyway!
Giovanni

···

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Lars
O. Grobe
Sent: 07 April 2009 12:54
To: Radiance general discussion
Subject: Re: [Radiance-general] Radiance and irradiation

Hi!

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?

The same command works here. Most probably something is wrong with your
Radiance installation, the most common origin of all trouble are PATH
and RAYPATH settings not pointing to the right directories. But here we
hit a point that I cannot really help you - I have zero experience with
Radiance on Windows, and usually it is guaranteed 100% more pain for
doing the same. Can you check your installation?

CU Lars.

Hi!

Sounds quite different... I can't even find those files in my radiance
installation!!

These are not programs or files, RAYPATH and PATH are (required)
environment variables :wink: Is your radiance-installation functional?
Where did you get it from, by compiling it or bey downloading binaries?

CU Lars.

Giovanni, right-click on My Computer, select Properties, go to the
Advanced tab, click the Environment Variables button near the bottom. In
the upper window you should have a variable called PATH and a variable
called RAYPATH. If you don't have them, or the values don't match the
following, create or edit them accordingly...

PATH = .;C:\Program Files\MinGW-Radiance\bin;$PATH
RAYPATH = .;C:\Program Files\MinGW-Radiance\lib

At least that's how it's set up on mine using the MingW binaries from
http://www.bozzograo.net/radiance/
If your radiance bin or lib directories are located elsewhere on your C
drive, change accordingly.

···

-------------------------------------
Giovanni Betti
Sent: Tuesday, April 07, 2009 9:02 AM

Sounds quite different... I can't even find those files in my radiance
installation!!
Thanks anyway!
Giovanni

-------------------------
Lars O. Grobe
Sent: 07 April 2009 12:54

The same command works here. Most probably something is wrong with your
Radiance installation, the most common origin of all trouble are PATH
and RAYPATH settings not pointing to the right directories. But here we
hit a point that I cannot really help you - I have zero experience with
Radiance on Windows, and usually it is guaranteed 100% more pain for
doing the same. Can you check your installation?

CU Lars.

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Giovanni,

I have the windows version of radiance on my machine. I don't think it comes with false color. I believe this is because false color is a c-shell script and windows does not use C-shells, it uses the dos prompt instead. If I were you, I would look into adding Cygwin to your windows computer and installing radiance within Cygwin. Then you would have the full functionality of radiance on a windows machine. (This is what I do and it works great) (And is free) You could also set up a dual boot on your machine and either boot radiance or boot linux (not a practical solution in my opinion) (also free). Or you could use VMware and run both windows and linux simultaneously. This is possibly the best option, but I've never tried it since I don't own a copy of VMware. (not free)

As far as the Cygwin option goes, I have not been able to compile radiance on Cygwin myself and have relied on the link below. I would love to know how it was done. I have however, been able to compile radiance on Suse Linux...

For Cygwin radiance see... http://www.dream.unipa.it/dream/pub/dot/anselmo/radiance/03.php and follow the link (http://www.bozzograo.net/radiance/) to the updated binaries. (Thanks again to Francesco Anselmo for those)

For Cygwin go to www.cygwin.com

Good luck!

Mark de la Fuente

PS.. as a side note, I find the hdrview program (http://www.debevec.org/FiatLux/hdrview/) to be very useful as well. It's too bad you can't print from there though. Anyone know of a windows viewer that allows you to adjust the exposure of an image and also print?

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Mark de la Fuente wrote:

PS.. as a side note, I find the hdrview program (http://www.debevec.org/FiatLux/hdrview/) to be very useful as well. It's too bad you can't print from there though. Anyone know of a windows viewer that allows you to adjust the exposure of an image and also print?

The Radiance front end Rayfront has a Windows binary called "winimage" that allows one to open a Radiance .pic -- excuse me, .hdr -- image and do exposure adjustments, do the pcond -h tonemapping, and generate falsecolor images which can be printed and saved in alternate formats. It's part of the Rayfront program and AFAIK it's not available as a standalone program. Details on Rayfront are located here:

http://www.schorsch.com/rayfront/

Schorsch? Any chance of spinning that off into a separate purchase/download (or updating RF to work on newer versions of AutoCAD)?

- Rob Guglielmetti

I'm afraid to mention it, but I think the old "Desktop Radiance" package
came with winimage. If required you could download that big package,
take the winimage.exe from it, and delete the rest of the obsolete
package.

Maybe it's possible to package separately, not necessarily from
Rayfront? Or maybe my memory is just mixed up.

···

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Rob
Guglielmetti
Sent: Tuesday, April 07, 2009 12:19 PM
To: Radiance general discussion
Subject: Re: [Radiance-general] Radiance and irradiation

Mark de la Fuente wrote:

PS.. as a side note, I find the hdrview program
(http://www.debevec.org/FiatLux/hdrview/) to be very useful as well.
It's too bad you can't print from there though. Anyone know of a
windows viewer that allows you to adjust the exposure of an image and
also print?

The Radiance front end Rayfront has a Windows binary called "winimage"
that allows one to open a Radiance .pic -- excuse me, .hdr -- image and
do exposure adjustments, do the pcond -h tonemapping, and generate
falsecolor images which can be printed and saved in alternate formats.
It's part of the Rayfront program and AFAIK it's not available as a
standalone program. Details on Rayfront are located here:

http://www.schorsch.com/rayfront/

Schorsch? Any chance of spinning that off into a separate
purchase/download (or updating RF to work on newer versions of AutoCAD)?

- Rob Guglielmetti

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Christopher Rush wrote:

I'm afraid to mention it, but I think the old "Desktop Radiance" package
came with winimage. If required you could download that big package,
take the winimage.exe from it, and delete the rest of the obsolete
package.

Maybe it's possible to package separately, not necessarily from
Rayfront? Or maybe my memory is just mixed up.

Oh, you're right Christopher! I think the one that shipped with Rayfront may have been updated but in general it's the same application. So I suppose one could install DR to get the winimage.exe.

I guess my memory is starting to fade...

- Rob

Hi,

For Radiance images preview and analysis in Windows and Linux you can use
free tool RadDisplay <http://deluminaelab.com/en/tools.html>
It has graphical user interface, and you can make false color images with
various palettes.
You can also adjust image exposure, trace pixels, and preview either
(ir)radiance or (il)luminace values.
Current version can only save images in jpg format, but we are preparing new
version that can also save in .pic/.hdr file format.

For now it doesn't offer possibility to print images, but thank you for
idea. We'll try to implement it in next version of the program.

Hope it helps!

Marija