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Thread: how to straighten my image in ptgui.

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fatchai

Posts: 348
Location: n/a, Hong Kong
Registered: 17 Mar 2005
how to straighten my image in ptgui.
Posted: 15 Apr 2006 at 3:59 GMT
my pano looks like this after i stitched it in ptgui.



how can i straighten it ? normally i tried to press the level icon in the pt editor but the image doesn't change this time.

i saw some website teach user to add a horizontial control point...but is it possible to add that in my pano?

thanks alot
fatchai.
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: how to straighten my image in ptgui.
Posted: 15 Apr 2006 at 5:42 GMT
You can level a panorama during the stitching process or you can level a finished stitched image. In the latter case, you just start a new project with the stitched image: specify the lens type as equirectangular with a fov of 360, set the rest of the lens parameters to zero and the output panorama to be equirectangular 360x180.

The method is exactly the same in either case. You add some t1 (vertical line) control points to some vertically aligned features like the sides of door frames and windows or edges of walls. In outdoor scenes with level stretches of water, there may well be objects reflected in the water and these will necessarily be vertically aligned and are good candidates for assigning t1 points. If the actual horizon is visible, you can assign t2 points along it instead of or as well as t1 points on verticals.

To assign a t1 point, set the control point type to vertical line, display the same feature to be marked in both control point windows (displaying the same or different images as necessary). Click at one end of the line feature in one window and then click the other end of the line in the other window. (You don't have to click the actual ends of the feature, just somewhere along the edge near the ends). That creates one t1 control point. Assigning t1 points on two features separated by approximately 90 degrees of yaw are enough to level the panorama. Two separated by exactly 180 degrees of yaw will not work. Assigning three t1 points will therefore guarantee success.

You then run the optimizer after checking y,p,r on all images except uncheck y on the anchor image (any image). If you are levelling a single image, then you just optimize p and r and leave y unchecked. Don't include any other parameters for optimization.

That's all. To understand why this all works, see the Guide to the Optimizer at:
homepage.ntlworld.com/j.houghton/optitute.htm
also
homepage.ntlworld.com/j.houghton/horizons.htm
and the Pano Tools Wiki at
tinyurl.com/5ru9w

John
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fatchai

Posts: 348
Location: n/a, Hong Kong
Registered: 17 Mar 2005
Re: how to straighten my image in ptgui.
Posted: 16 Apr 2006 at 3:37 GMT
hi John :

good reply. thaks. it seen i have generated diff results when i used both single and multi images to level in ptgui. for single image, it left a bigger dark patch after the image has leveled by the optimzer.
see example below.





chees
fatchai
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John Houghton

Posts: 3934
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
Re: how to straighten my image in ptgui.
Posted: 16 Apr 2006 at 6:54 GMT
Fatchai, For levelling the single image, check your settings. You may have the lens parameters set incorrectly. a=b=c=0 and FOV=360 equirectangular. I get this result:



John
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