Questions about image size

Hello everyone,

I'm trying to generate a rendering from the following command:
rpict -x 786 -y 576 -ab 4 -ad 1024 -vtv -vp 14.636 -5.376 4.226 -vd
-14.504 13.433 -4.304 -vu 0 0 1 -vh 35.0 -vv 35.0 -vo 0 -va 0 -vs 0
-vl 0 -bv-

However, the pic file generated is in size 576x576. Could anyone tell
why Radiance did this? Thanks.

Yu Sheng

Hi,

You have a rectangle image description when specifying your -x and -y
values but your -vh and -vv values describe a square image. I think you
just need to delete your -y variable and you should then get a square
image. If you want a rectangle image then find the ratio between your
-x and -y value and apply the same ratio between your -vh and -vv
values.

I hope that makes sense.

Andrew

···

__________________________
Andrew Bissell
B.Eng(Hons) C.Eng MSLL MCIBSE MIET
Associate Lighting Designer
Cundall Light4
Direct: 0161 200 1235
Mobile: 07899 907 978
Office: 0161 244 5660
P Please consider the environment before printing this e-mail

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Sheng
Yu
Sent: 03 December 2008 16:47
To: [email protected]
Subject: [Radiance-general] Questions about image size

Hello everyone,

I'm trying to generate a rendering from the following command:
rpict -x 786 -y 576 -ab 4 -ad 1024 -vtv -vp 14.636 -5.376 4.226 -vd
-14.504 13.433 -4.304 -vu 0 0 1 -vh 35.0 -vv 35.0 -vo 0 -va 0 -vs 0
-vl 0 -bv-

However, the pic file generated is in size 576x576. Could anyone tell
why Radiance did this? Thanks.

Yu Sheng

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Good start, but the formula is just a little more complicated for perspective (-vtv) views. See:

  http://radsite.lbl.gov/radiance/digests_html/v2n7.html#VIEW_ANGLES

-Greg

···

From: "Bissell, Andrew" <[email protected]>
Date: December 3, 2008 8:53:07 AM PST

Hi,

You have a rectangle image description when specifying your -x and -y
values but your -vh and -vv values describe a square image. I think you
just need to delete your -y variable and you should then get a square
image. If you want a rectangle image then find the ratio between your
-x and -y value and apply the same ratio between your -vh and -vv
values.

I hope that makes sense.

Andrew

-----Original Message-----
[mailto:[email protected]] On Behalf Of Sheng
Yu
Sent: 03 December 2008 16:47

Hello everyone,

I'm trying to generate a rendering from the following command:
rpict -x 786 -y 576 -ab 4 -ad 1024 -vtv -vp 14.636 -5.376 4.226 -vd
-14.504 13.433 -4.304 -vu 0 0 1 -vh 35.0 -vv 35.0 -vo 0 -va 0 -vs 0
-vl 0 -bv-

However, the pic file generated is in size 576x576. Could anyone tell
why Radiance did this? Thanks.

Yu Sheng

Hi Yu Sheng,

As Andrew pointed out, you need to calculate the correct -vh and -vv values for your "camera" as well. Calculating the ratio of the image dimensions and simply apply these on the -vv and -vh values is not the best solution, however. There has been a discussion about this topic on radiance-online.org. Please also have a look at the attachment, which "implements" this discussion in a little tool that will calculate the correct vertical view angle, when a horizontal view angle and the image dimensions are given. I hope this makes sense to you.

-Iebele

Sheng Yu wrote:

viewsize.cpp (873 Bytes)

···

Hello everyone,

I'm trying to generate a rendering from the following command:
rpict -x 786 -y 576 -ab 4 -ad 1024 -vtv -vp 14.636 -5.376 4.226 -vd
-14.504 13.433 -4.304 -vu 0 0 1 -vh 35.0 -vv 35.0 -vo 0 -va 0 -vs 0
-vl 0 -bv-

However, the pic file generated is in size 576x576. Could anyone tell
why Radiance did this? Thanks.

Yu Sheng

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general

Also keep in mind that you should be able to let rpict size your image
according to the view to fit within the x and y dimensions given. If you
know that you want an image 786 pixels wide, with any arbitrary
horizontal and vertical view angles, you could use options like:

-x 786 -y 10000 -vh [anglex] -vv [angley]

where the values in brackets are whatever view angles you want. This
will fit the image to the horizontal and allow the image to be whatever
vertical size it takes to meet your view angle parameters (in this case
with a cap of 10000 pixels). This works based on the default pixel
aspect of -pa 1. This way if the vh and vv are equal, it generates a
square, otherwise it will make an appropriately sized rectangular image.

···

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Greg
Ward
Sent: Wednesday, December 03, 2008 12:16 PM
To: Radiance general discussion
Subject: Re: [Radiance-general] Questions about image size

Good start, but the formula is just a little more complicated for
perspective (-vtv) views. See:

http://radsite.lbl.gov/radiance/digests_html/v2n7.html#VIEW_ANGLES

-Greg

From: "Bissell, Andrew" <[email protected]>
Date: December 3, 2008 8:53:07 AM PST

Hi,

You have a rectangle image description when specifying your -x and -y
values but your -vh and -vv values describe a square image. I think
you just need to delete your -y variable and you should then get a
square image. If you want a rectangle image then find the ratio
between your -x and -y value and apply the same ratio between your -vh

and -vv values.

I hope that makes sense.

Andrew

-----Original Message-----
[mailto:[email protected]] On Behalf Of
Sheng Yu
Sent: 03 December 2008 16:47

Hello everyone,

I'm trying to generate a rendering from the following command:
rpict -x 786 -y 576 -ab 4 -ad 1024 -vtv -vp 14.636 -5.376 4.226 -vd
-14.504 13.433 -4.304 -vu 0 0 1 -vh 35.0 -vv 35.0 -vo 0 -va 0 -vs 0
-vl 0 -bv-

However, the pic file generated is in size 576x576. Could anyone tell
why Radiance did this? Thanks.

Yu Sheng

_______________________________________________
Radiance-general mailing list
[email protected]
http://www.radiance-online.org/mailman/listinfo/radiance-general
____________________________________________________________
Electronic mail messages entering and leaving Arup business
systems are scanned for acceptability of content and viruses