Any way to specify arbitrary pole positions?

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Any way to specify arbitrary pole positions?

PanoTools NG mailing list
Hello,
 

 I'm new to the group, apologies if this question doesn't make sense.
 

 I was wondering if anyone knew of a way to specify arbitrary pole positions i.e. to position the zenith/nadir at any position on the sphere when projecting to equirectangular. In tools such as Hugin I can change the yaw, pitch and roll, but this assumes I want the poles to be opposite each other across the sphere.
 

 Any ideas?
 

 Many thanks,
 
 Drew
 

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Re: Any way to specify arbitrary pole positions?

PanoTools NG mailing list
Am 18.05.2015 um 11:55 schrieb [hidden email]:
> I was wondering if anyone knew of a way to specify arbitrary pole
> positions i.e. to position the zenith/nadir at any position on the
> sphere when projecting to equirectangular. In tools such as Hugin I can
> change the yaw, pitch and roll, but this assumes I want the poles to be
> opposite each other across the sphere.

The poles are always opposite to each other on a sphere, that's it's
nature. How in your opinion should a sphere look like where the poles
are not opposite?

--
Erik Krause
http://www.erik-krause.de
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Re: Any way to specify arbitrary pole positions?

PanoTools NG mailing list
Hi Erik,

 Thanks for your reply! Sorry I've not explained myself very well, and I think I'm using some terminology incorrectly.
 

 What I'm trying to do is project a spherical image to a different representation. Normally when you project from a sphere to equirectangular, the zenith is stretched across the top of the image and the nadir is stretched across the bottom. What I want to do is select two arbitrary points on the sphere to become stretched across the top and bottom of this new projection, and have the rest of the image distort as required. This would have the same effect as choosing arbitrary poles on a sphere and projecting to equirectangular, but you're right calling these "poles" is confusing because they're not opposite on the sphere.
 

 I'm not sure if this clears things up - if not let me know and I can maybe sketch something to illustrate what I'm trying to say.
 

 Thanks again,
 Drew
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Re: Any way to specify arbitrary pole positions?

PanoTools NG mailing list
Am 19.05.2015 um 00:51 schrieb [hidden email]:

> What I'm trying to do is project a spherical image to a different
> representation. Normally when you project from a sphere to
> equirectangular, the zenith is stretched across the top of the image
> and the nadir is stretched across the bottom. What I want to do is
> select two arbitrary points on the sphere to become stretched across
> the top and bottom of this new projection, and have the rest of the
> image distort as required. This would have the same effect as
> choosing arbitrary poles on a sphere and projecting to
> equirectangular, but you're right calling these "poles" is confusing
> because they're not opposite on the sphere.

I can not imagine what this should be good for. However, some thoughts:
Any point inside an equirectangular image can be the new pole. The other
pole will automatically be 180° away from this first pole, no matter
what you do.

If you choose two points not 180° apart and make them poles (which is
what you do if you stretch them across bottom and top of an equirect),
you'd need to stretch the area where the points are nearer to each other
and compress the area on the other side (a sphere is round, remember!).
This implies the distortion of all other areas. While this is feasible
it can't be done with any panotools based program. You'd need to figure
out the math for yourself, I can't, it's way beyond my scope. Eventually
you could use matlab to do something like that.

Anyway I'd be curious what you want to achieve...

--
Erik Krause
http://www.erik-krause.de
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Re: Any way to specify arbitrary pole positions?

PanoTools NG mailing list
In reply to this post by PanoTools NG mailing list
That sounds like just a numerical transform of the spherical image.

That’s what the function is called in PTGUI. I have no idea how to do this in Hugin.

To be fair, I don’t think many people here use hugin.

It’s free yes. But PTGUI is more intuitive and quickly pays for itself in time saved and features.

 

Best Regards,

 

Sacha Griffin

Southern Digital Solutions LLC  - Atlanta, Georgia

http://www.seeit360.com <http://www.seeit360.com/>

http://twitter.com/SeeIt360

http://www.facebook.com/SeeIt360

IM: [hidden email]

Office: 404-551-4275

 

 

From: [hidden email] [mailto:[hidden email]]
Sent: Monday, May 18, 2015 6:52 PM
To: [hidden email]
Subject: [PanoToolsNG] Re: Any way to specify arbitrary pole positions?

 

 

Hi Erik,

 

Thanks for your reply! Sorry I've not explained myself very well, and I think I'm using some terminology incorrectly.

 

What I'm trying to do is project a spherical image to a different representation. Normally when you project from a sphere to equirectangular, the zenith is stretched across the top of the image and the nadir is stretched across the bottom. What I want to do is select two arbitrary points on the sphere to become stretched across the top and bottom of this new projection, and have the rest of the image distort as required. This would have the same effect as choosing arbitrary poles on a sphere and projecting to equirectangular, but you're right calling these "poles" is confusing because they're not opposite on the sphere.

 

I'm not sure if this clears things up - if not let me know and I can maybe sketch something to illustrate what I'm trying to say.

 

Thanks again,

Drew



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Re: Any way to specify arbitrary pole positions?

PanoTools NG mailing list
In reply to this post by PanoTools NG mailing list
If someone takes a pano, using a pole held at an angle (say 45 degrees) the Zenith and Nadir (top and bottom) no longer line up with the Sky and Earth. This can be compensated, using: Roll, Pitch, and Yaw.

In your case, it sounds like you want to play with these settings to deliberately move the Sky and Earth points around in the panograph.

--Alan