[HDRI] Convert equisolidangular to equiangular projection

Discussion:

Zhe Kong

2017-01-25 21:15:49 UTC

Dear list:
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

Gregory J. Ward

2017-01-26 00:48:55 UTC

Permalink

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

Date: January 25, 2017 1:15:49 PM PST
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?
2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe

J. Alstan Jakubiec

2017-01-26 05:57:36 UTC

Permalink

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am
having trouble finding a source from Sigma right now, but Cauwerts,
Bodart and Deneyer's paper
<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.

That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each
source jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan

Post by Gregory J. Ward
Hi Zhe,
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

Claus Brøndgaard Madsen

2017-01-26 10:17:01 UTC

Permalink

If it is of any interest I did this overview some years back concerning various projections

[cid:***@01D277C5.B71699A0]

Claus B. Madsen

Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: ***@create.aau.dk<mailto:***@create.aau.dk>

Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <***@jakubiec.net>
Reply-To: High Dynamic Range Imaging <***@radiance-online.org>
Date: Thursday, 26 January 2017 at 06.57
To: "***@radiance-online.org" <***@radiance-online.org>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \

| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180Â° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,

-Greg

From: Zhe Kong <***@gmail.com><mailto:***@gmail.com>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

***@radiance-online.org<mailto:***@radiance-online.org>

http://www.radiance-online.org/mailman/listinfo/hdri

Tobias Porsch

2017-01-27 10:17:11 UTC

Permalink

Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

Von: J. Alstan Jakubiec [mailto:***@jakubiec.net]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: ***@radiance-online.org
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \

| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.

Cheers,

-Greg

From: Zhe Kong <***@gmail.com><mailto:***@gmail.com>

Date: January 25, 2017 1:15:49 PM PST

Dear list:

I am trying to compare HDR images and simulated luminance maps. Since I use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular project. I see very useful information from the post below:

https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html

However, I still have some questions need to figure out.

1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.

Zhe

_______________________________________________

HDRI mailing list

***@radiance-online.org<mailto:***@radiance-online.org>

http://www.radiance-online.org/mailman/listinfo/hdri

J. Alstan Jakubiec

2017-01-27 10:26:37 UTC

Permalink

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't
measured them for vignetting and angular verification yet. It is on my
to do list :). I will be disappointed if they are equi-solid angular
however. Will let you know sometime after the Lunar new year.

Alstan

Post by Tobias Porsch
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens
is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an
equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?
Cheers
Tobias
*Gesendet:* Donnerstag, 26. Januar 2017 06:58
*Betreff:* Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I
am having trouble finding a source from Sigma right now, but Cauwerts,
Bodart and Deneyer's paper
<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each
source jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.
Best,
Alstan
Hi Zhe,
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.
Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?
2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

J. Alstan Jakubiec

2017-01-27 10:33:27 UTC

Permalink

A little followup that is worth noting is that Axel Jacobs measured the
Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here:
https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

Post by J. Alstan Jakubiec
Hi Tobias,
I just purchased a pair of Sigma 8mm f/3.5's for my work, but I
haven't measured them for vignetting and angular verification yet. It
is on my to do list :). I will be disappointed if they are equi-solid
angular however. Will let you know sometime after the Lunar new year.
Alstan

Post by Tobias Porsch
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5
lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an
equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?
Cheers
Tobias
*Gesendet:* Donnerstag, 26. Januar 2017 06:58
*Betreff:* Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I
am having trouble finding a source from Sigma right now, but
Cauwerts, Bodart and Deneyer's paper
<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each
source jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.
Best,
Alstan
Hi Zhe,
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.
Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?
2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

Claus Brøndgaard Madsen

2017-01-27 12:49:33 UTC

Permalink

Hi everyone,

Some years ago I tested my Sigma 8mm lens, f3.5.

At the time I found several sources online claiming it to be equi-solid angle (-vth), but it didnât match my personal experiences with the lens, so I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.

Cheers,
Claus

Claus B. Madsen

Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: ***@create.aau.dk<mailto:***@create.aau.dk>

Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <***@jakubiec.net>
Reply-To: High Dynamic Range Imaging <***@radiance-online.org>
Date: Friday, 27 January 2017 at 11.33
To: "***@radiance-online.org" <***@radiance-online.org>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote:

Hi Tobias,

I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.

Alstan

On 1/27/2017 6:17 PM, Tobias Porsch wrote:
Hi Alstan,

I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?

Cheers
Tobias

Von: J. Alstan Jakubiec [mailto:***@jakubiec.net]
Gesendet: Donnerstag, 26. Januar 2017 06:58
An: ***@radiance-online.org<mailto:***@radiance-online.org>
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi Zhe,

As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
On 1/26/2017 8:48 AM, Gregory J. Ward wrote:

Hi Zhe,

You should be able to apply the fisheye_corr.cal file I gave you earlier to correct the distortion and make it an angular fisheye image that pinterp works with. (Why you need pinterp, I am not sure.) The command is as suggested in the fisheye_corr.cal file itself:

pcomb -f fisheye_corr.cal -o fisheye.hdr \

| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

Raquel Viula

2017-01-27 13:49:57 UTC

Permalink

Hi all,
Thank you for raising this topic and sharing your views. I¹m using the
output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.
May I ask why people refer to -vth as equi-solid angle and not hemispherical
as it is defined in Radiance¹s rpict man page?
My understanding from that page and from Axel Jacobs' presentation sent via
the link just before is that there isn't a Radiance description for the
equi-solid angle view.

Best Regards

Raquel Viula

PhD Researcher

TU Delft | Faculty of Architecture and the Built Environment |

Architectural Engineering and Technology

Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA
Delft

From: Claus Brøndgaard Madsen <***@create.aau.dk>
Reply-To: High Dynamic Range Imaging <***@radiance-online.org>
Date: Friday 27 January 2017 13:49
To: High Dynamic Range Imaging <***@radiance-online.org>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Hi everyone,

Some years ago I tested my Sigma 8mm lens, f3.5.

At the time I found several sources online claiming it to be equi-solid
angle (-vth), but it didn¹t match my personal experiences with the lens, so
I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular
fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.

Cheers,
Claus

Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology

Phone: +45 9940 8788 | E-mail: ***@create.aau.dk <mailto:***@create.aau.dk>
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark

Employee No.: 107255 | Vat No.: DK29102384

From: "J. Alstan Jakubiec" <***@jakubiec.net>
Reply-To: High Dynamic Range Imaging <***@radiance-online.org>
Date: Friday, 27 January 2017 at 11.33
To: "***@radiance-online.org" <***@radiance-online.org>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

A little followup that is worth noting is that Axel Jacobs measured the
Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here:
https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jac
obs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan

Post by J. Alstan Jakubiec
Hi Tobias,
I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't
measured them for vignetting and angular verification yet. It is on my to do
list :). I will be disappointed if they are equi-solid angular however. Will
let you know sometime after the Lunar new year.
Alstan

Post by Tobias Porsch
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an
equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant
(-angular) (-vta) lens.
Can you please double-check that issue for me?
Cheers
Tobias
Gesendet: Donnerstag, 26. Januar 2017 06:58
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and
the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble
finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's
paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002>
says so.
That said, if you do end up with an equi-solidangle image, I have a python
script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.
Best,
Alstan

Post by Gregory J. Ward
Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier to
correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/
011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe

_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

_______________________________________________ HDRI mailing list
***@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/hdri

Gregory J. Ward

2017-01-27 16:10:53 UTC

Permalink

Raquel points out an important error in this discussion's terminology. The "equidistant" fisheye does indeed correspond to the "-vta" view type in Radiance. However, the "-vth" type corresponds to a hemispherical projection, which very few commercial fisheye lenses realize. In particular, the equisolidangle projection is much closer to "-vta" than it is to "-vth". If your lens is equisolidangle, then you need to use the fisheye_corr.cal script or similar to convert it to an equidistant projection.

I have not implemented the equisolidangle projection, though there is a third fisheye type (-vts) which is called "stereographic", although we prefer the term "planisphere" projection to avoid confusion with stereo views. This does not correspond to any commercial lenses to my knowledge, but I'd be interested to hear of one.

Date: January 27, 2017 5:49:57 AM PST
Hi all,
Thank you for raising this topic and sharing your views. Im using the output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via Evalglare that should require a -vth or -vta view, so this is critical information for me.
May I ask why people refer to -vth as equi-solid angle and not hemispherical as it is defined in Radiances rpict man page?
My understanding from that page and from Axel Jacobs' presentation sent via the link just before is that there isn't a Radiance description for the equi-solid angle view.
Best Regards
Raquel Viula
PhD Researcher
TU Delft | Faculty of Architecture and the Built Environment |
Architectural Engineering and Technology
Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA Delft
Date: Friday 27 January 2017 13:49
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi everyone,
Some years ago I tested my Sigma 8mm lens, f3.5.
At the time I found several sources online claiming it to be equi-solid angle (-vth), but it didnt match my personal experiences with the lens, so I tested it.
My tests showed it to be equidistant (-vta), i.e. identical to the angular fish eye projection in RADIANCE.
So, in my experience, the 8mm Sigma lens is equidistant.
Cheers,
Claus
Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark
Employee No.: 107255 | Vat No.: DK29102384
Date: Friday, 27 January 2017 at 11.33
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf
Alstan
Hi Tobias,
I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't measured them for vignetting and angular verification yet. It is on my to do list :). I will be disappointed if they are equi-solid angular however. Will let you know sometime after the Lunar new year.
Alstan
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant (-angular) (-vta) lens.
Can you please double-check that issue for me?
Cheers
Tobias
Gesendet: Donnerstag, 26. Januar 2017 06:58
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's paper says so.
That said, if you do end up with an equi-solidangle image, I have a python script that converts equi-solid angle to equi-angle for each source jpeg while maintaining the EXIF data. I used this to convert equi-solidangle images from my Canon 8-15mm fisheye lenses.
Best,
Alstan
Hi Zhe,
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180° to black, assuming that is what you want. It assumes that you have already cropped the image to a minimum square area. You should apply vignetting correction and absolute calibration first.
Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation needs to be applied to the function. Greg mentioned this simple expression, sin(theta)/theta, but I am still confused. Could anyone offer me the command?
2) The post discussed the steps of processing HDR images. If I get it right, the steps following "adjust exposure" are vignetting correction, adding view information, converting project from equisolidangular to equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record the luminance value on a grey card for calibration. My question is, should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe
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Zhe Kong

2017-01-27 02:35:26 UTC

Permalink

Hello Greg:
Thank you very much for your answer. I will explore more about
fisheye_corr.cal.

Hello Alstan:
Thank you for your explanation. I got this information from the
manufacturer, but based on the paper you sent, I made a mistake. Thank you
for saving my time and effort.

Zhe

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1. Convert equisolidangular to equiangular projection (Zhe Kong)
2. Re: Convert equisolidangular to equiangular projection
(Gregory J. Ward)
3. Re: Convert equisolidangular to equiangular projection
(J. Alstan Jakubiec)
4. Re: Convert equisolidangular to equiangular projection
(Claus Br?ndgaard Madsen)
----------------------------------------------------------------------
Message: 1
Date: Wed, 25 Jan 2017 15:15:49 -0600
Subject: [HDRI] Convert equisolidangular to equiangular projection
gmail.com>
Content-Type: text/plain; charset="utf-8"
I am trying to compare HDR images and simulated luminance maps. Since I use
SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe
-------------- next part --------------
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------------------------------
Message: 2
Date: Wed, 25 Jan 2017 16:48:55 -0800
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Content-Type: text/plain; charset=iso-8859-1
Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I

use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to

https://www.radiance-online.org:447/pipermail/radiance-

general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation

needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it

right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?

Any suggestions or explanation would be appreciated.
Zhe

------------------------------
Message: 3
Date: Thu, 26 Jan 2017 13:57:36 +0800
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Content-Type: text/plain; charset="windows-1252"; Format="flowed"
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)
lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am
having trouble finding a source from Sigma right now, but Cauwerts,
Bodart and Deneyer's paper
<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> says
so.
That said, if you do end up with an equi-solidangle image, I have a
python script that converts equi-solid angle to equi-angle for each
source jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.
Best,
Alstan

Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier

to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as

pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180? to black, assuming that is

what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.

Cheers,
-Greg

Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I

use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to

https://www.radiance-online.org:447/pipermail/radiance-

general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation

needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it

Any suggestions or explanation would be appreciated.
Zhe

_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

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------------------------------
Message: 4
Date: Thu, 26 Jan 2017 10:17:01 +0000
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Content-Type: text/plain; charset="utf-8"
If it is of any interest I did this overview some years back concerning
various projections
Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark
Employee No.: 107255 | Vat No.: DK29102384
Date: Thursday, 26 January 2017 at 06.57
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens,
and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having
trouble finding a source from Sigma right now, but Cauwerts, Bodart and
Deneyer's paper<http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.
2012.08.03.002> says so.
That said, if you do end up with an equi-solidangle image, I have a python
script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.
Best,
Alstan
Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier
to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as
pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180? to black, assuming that is
what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.
Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I
use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to
https://www.radiance-online.org:447/pipermail/radiance-
general/2015-August/011184.html
However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation
needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?
2) The post discussed the steps of processing HDR images. If I get it
right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to
record the luminance value on a grey card for calibration. My question is,
should I calibrate the image before or after converting fisheye projection?
Any suggestions or explanation would be appreciated.
Zhe
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
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------------------------------
Subject: Digest Footer
_______________________________________________
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------------------------------
End of HDRI Digest, Vol 87, Issue 1
***********************************

--
*Zhe Kong*
*PhD Student*
*University of Wisconsin - Milwaukee *
*School of Architecture and Urban Planning *
*2131 E. Hartford Ave, Milwaukee, WI 53211 *
*Office 327*

Zhe Kong

2017-01-28 01:09:54 UTC

Permalink

Sorry about the confusion I brought up. I got this wrong information from
the manufacturer. If I recall my previous experience, Sigma f/3.5 matches
Radiance -vta pretty well. The current mismatch might be caused by the
camera coordinate in the simulation.
Anyway, Happy Chinese New Year, everyone!

Zhe

Date: January 27, 2017 5:49:57 AM PST
Hi all,
Thank you for raising this topic and sharing your views. I?m using the

output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.

May I ask why people refer to -vth as equi-solid angle and not

hemispherical as it is defined in Radiance?s rpict man page?

My understanding from that page and from Axel Jacobs' presentation sent

via the link just before is that there isn't a Radiance description for the
equi-solid angle view.

Best Regards
Raquel Viula
PhD Researcher
TU Delft | Faculty of Architecture and the Built Environment |
Architectural Engineering and Technology
Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA

Delft

Date: Friday 27 January 2017 13:49
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi everyone,
Some years ago I tested my Sigma 8mm lens, f3.5.
At the time I found several sources online claiming it to be equi-solid

angle (-vth), but it didn?t match my personal experiences with the lens, so
I tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the

angular fish eye projection in RADIANCE.

So, in my experience, the 8mm Sigma lens is equidistant.
Cheers,
Claus
Claus B. Madsen
Assoc. Prof., Ph.D. | Department of Architecture and Media Technology
Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark
Employee No.: 107255 | Vat No.: DK29102384
Date: Friday, 27 January 2017 at 11.33
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection
A little followup that is worth noting is that Axel Jacobs measured the

Sigma 4.5mm and found it to have an equi-solid angle projection. See his
presentation here: https://www.radiance-online.
org/community/workshops/2012-copenhagen/Day2/Jacobs/Jacobs-
AJ09-HDR_Radiance_WS-2012.pdf

Alstan
Hi Tobias,
I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't

measured them for vignetting and angular verification yet. It is on my to
do list :). I will be disappointed if they are equi-solid angular however.
Will let you know sometime after the Lunar new year.

Alstan
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens

is an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an
equi-distant (-angular) (-vta) lens.

Can you please double-check that issue for me?
Cheers
Tobias
Gesendet: Donnerstag, 26. Januar 2017 06:58
Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection
Hi Zhe,
As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta)

lens, and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am
having trouble finding a source from Sigma right now, but Cauwerts, Bodart
and Deneyer's paper says so.

That said, if you do end up with an equi-solidangle image, I have a

python script that converts equi-solid angle to equi-angle for each source
jpeg while maintaining the EXIF data. I used this to convert
equi-solidangle images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier

to correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as

pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180? to black, assuming that is

what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.

Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I

use SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to

https://www.radiance-online.org:447/pipermail/radiance-

general/2015-August/011184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation

needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the
command?

2) The post discussed the steps of processing HDR images. If I get it

Any suggestions or explanation would be appreciated.
Zhe
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________
HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri
_______________________________________________ HDRI mailing list

org/mailman/listinfo/hdri _______________________________________________

HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

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------------------------------
Subject: Digest Footer
_______________________________________________
HDRI mailing list
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------------------------------
End of HDRI Digest, Vol 87, Issue 6
***********************************

--
*Zhe Kong*
*PhD Student*
*University of Wisconsin - Milwaukee *
*School of Architecture and Urban Planning *
*2131 E. Hartford Ave, Milwaukee, WI 53211 *
*Office 327*

Raquel Viula

2017-01-29 07:22:21 UTC

Permalink

Hi Zhe, I¹m glad you brought this up and thank you Greg for the
clarification.

Best Regards

Raquel

Raquel Viula

PhD Researcher

TU Delft | Faculty of Architecture and the Built Environment |

Architectural Engineering and Technology

Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA Delf

From: Zhe Kong <***@gmail.com>
Reply-To: High Dynamic Range Imaging <***@radiance-online.org>
Date: Saturday 28 January 2017 02:09
To: <***@radiance-online.org>
Subject: Re: [HDRI] Convert equisolidangular to equiangular projection

Sorry about the confusion I brought up. I got this wrong information from
the manufacturer. If I recall my previous experience, Sigma f/3.5 matches
Radiance -vta pretty well. The current mismatch might be caused by the
camera coordinate in the simulation.
Anyway, Happy Chinese New Year, everyone!

Zhe

Post by Raquel Viula

Date: January 27, 2017 5:49:57 AM PST
Hi all,
Thank you for raising this topic and sharing your views. I?m using the

output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via
Evalglare that should require a -vth or -vta view, so this is critical
information for me.

May I ask why people refer to -vth as equi-solid angle and not

hemispherical as it is defined in Radiance?s rpict man page?

My understanding from that page and from Axel Jacobs' presentation sent via

the link just before is that there isn't a Radiance description for the
equi-solid angle view.

Delft

angle (-vth), but it didn?t match my personal experiences with the lens, so I
tested it.

My tests showed it to be equidistant (-vta), i.e. identical to the angular

fish eye projection in RADIANCE.

Sigma 4.5mm and found it to have an equi-solid angle projection. See his
https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jaco
bs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf

Alstan
Hi Tobias,
I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't

measured them for vignetting and angular verification yet. It is on my to do
list :). I will be disappointed if they are equi-solid angular however. Will
let you know sometime after the Lunar new year.

Alstan
Hi Alstan,
I'm not sure if your below description is correct.
In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is

an equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant
(-angular) (-vta) lens.

and the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having
trouble finding a source from Sigma right now, but Cauwerts, Bodart and
Deneyer's paper says so.

That said, if you do end up with an equi-solidangle image, I have a python

script that converts equi-solid angle to equi-angle for each source jpeg
while maintaining the EXIF data. I used this to convert equi-solidangle
images from my Canon 8-15mm fisheye lenses.

Best,
Alstan
Hi Zhe,
You should be able to apply the fisheye_corr.cal file I gave you earlier to

correct the distortion and make it an angular fisheye image that pinterp
works with. (Why you need pinterp, I am not sure.) The command is as

pcomb -f fisheye_corr.cal -o fisheye.hdr \
| getinfo -a "VIEW= -vta -vh 180 -vv 180" \

corrected.hdr

This will also crop the area outside of 180? to black, assuming that is

what you want. It assumes that you have already cropped the image to a
minimum square area. You should apply vignetting correction and absolute
calibration first.

Cheers,
-Greg
Date: January 25, 2017 1:15:49 PM PST
I am trying to compare HDR images and simulated luminance maps. Since I use

SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to equiangular
https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/01
1184.html

However, I still have some questions need to figure out.
1) pinterp does not include equisolid-angular projection, so a equation

needs to be applied to the function. Greg mentioned this simple expression,
sin(theta)/theta, but I am still confused. Could anyone offer me the command?

2) The post discussed the steps of processing HDR images. If I get it

right, the steps following "adjust exposure" are vignetting correction,
adding view information, converting project from equisolidangular to
equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to record
the luminance value on a grey card for calibration. My question is, should I
calibrate the image before or after converting fisheye projection?

_______________________________________________

HDRI mailing list
http://www.radiance-online.org/mailman/listinfo/hdri

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------------------------------
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------------------------------
End of HDRI Digest, Vol 87, Issue 6
***********************************

--
Zhe Kong
PhD Student
University of Wisconsin - Milwaukee
School of Architecture and Urban Planning
2131 E. Hartford Ave, Milwaukee, WI 53211
Office 327
_______________________________________________ HDRI mailing list
***@radiance-online.org
http://www.radiance-online.org/mailman/listinfo/hdri