Sonic
Posts: 2
Location: Saint-Petersburg, Russian Federation
Registered: 5 Feb 2012
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Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 11:09 GMT
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Hey, everyone!
I'm currently using a Nikon D90 + Nikkor 20mm + EpicPro robotic panohead to shoot indoor spherical panoramas and ptgui to stich 'em, however, I'm not very deep into all this.
When stitching the panorama, I've faced a problem with straightening the lines. Here's the crop of the problem from the image:
It' a part of the ceiling and it's really hard to fix such problems in a stitched panorama using Photoshop or something like that.
What can I do to straighten the straight lines?
Using t3...tn 'straight line' control points to define a straight line doesn't provide any result and doesn't affect the final image at all.
Thank you for your advices.
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Smooth
Posts: 3773
Location: Mount Panorama, Australia
Registered: 21 Jul 2004
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 12:20 GMT
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This has nothing to do with T1, T2 or T3 straightening. Your issue with with stitching errors. Most likely because of incorrect (NPP) camera/lens set up on the panohead.
Possibly it is because you haven't checked the boxes for Horizontal and Vertical "shift" options in the advanced Optimizer of PTGui. Or possibly because of a poor spread or lack of control points.
Either way, it because of poor stitching.
Regards, Smooth 
www.omnipix.com.au
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Hans Nyberg
Posts: 2791
Location: Denmark
Registered: 28 Aug 2005
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 12:24 GMT
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1. Your panohead may not be correctly setup in NPP (Non Parallax Point)
2.You are not using PTGui correctly, maybe you do not optimize for shift or you may not have enough controlpoints on some images.
It may be a combination of both 1 and 2.
If your errors are only in areas with plain surfaces like the shown ones it is probably a lack of control points. You may need to ad CP manually.
PTgui can not automatically find control points in such areas.
Do not believe that because you have a robotic head it is also precise enough that you can stitch without control points.
Hans
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mediavets
Posts: 1980
Location: Isleham, Cambs., United Kingdom
Registered: 8 Feb 2008
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 12:36 GMT
updated: 5 Feb 2012 at 12:40 GMT
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Sonic said: Hey, everyone!
I'm currently using a Nikon D90 + Nikkor 20mm + EpicPro robotic panohead to shoot indoor spherical panoramas and ptgui to stich 'em
This is not a setup I'd choose to shoot indoor spherical panos.
Using a 20mm rectlinear lens on a Nikon DX cropped sensor body means you will require alot of images to cover 360x180 (a min. of 32 images?) and the FOV of each image will be relatively small (compared to a fisheye). So you will have a lot of seams and a lot of potential for images lacking features for automatic control point detection, for example on plain walls and ceilings.
Furthermore when shooting sphericals it is desirable to reduce the number of images per row as you approach the zenith and nadir to avoid excessive overlapping which can in itself cause problems when stitching.
As far as I know the Gigapan Epic Pro robotic pano head can only shoot a regular matrix/grid of images so you'll probably have excessive overlaps as you approach the zenith and nadir. It has a pretty large nadir footprint too.
Andrew
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John Houghton
Posts: 3487
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 12:50 GMT
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Sonic said: Using t3...tn 'straight line' control points to define a straight line doesn't provide any result and doesn't affect the final image at all.
Which optimizer are you using? The standard PTGui optimizer does not support t3...tn points. There is a special version of PTOptimizer (the Panorama Tools optimizer) that does support these points and that is available for download from the PTGui web site.
You need to exercise care in using these points because line features on the ceiling will not be straight in an equirectangular projection, though they might be considered to be straight over short distances.
As already suggested, the reason for the stitching errors might be due to inaccurate setup of the pano head, or maybe just unskilled use of the optimizer and assignments of control points. Another possibility might be that the zenith image is upside down with respect to all the other images (a result of duff data from the auto rotation sensor when the camera points directly up) - perhaps not likely with your automatic mechanism. Viewpoint correction in PTGui Pro might be helpful in aligning the zenith image, as there seem to be tiles to provide corner features for control points.
John
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Sonic
Posts: 2
Location: Saint-Petersburg, Russian Federation
Registered: 5 Feb 2012
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 22:28 GMT
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I managed to download and set up the PTOptimizer. But believe me, you don't want to see the results of using it.
Tomorrow I'll buy a 16mm f/2.8 lens 'Zenitar' and will try to retake the panorama and tell you about the results. Thanks!
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Jaime
Posts: 30
Location: Elche, Spain
Registered: 14 Sep 2011
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Re: Straightening the straight lines in ptgui
Posted: 5 Feb 2012 at 22:41 GMT
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For your cropped sensor you will be better with a samyang 8, a Nikon 10,5 or something similar, and pano head with a true NPP adjustment.
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Nick Fan
[NodalNinja]
Posts: 709
Location: Hong Kong
Registered: 26 May 2006
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Re: Straightening the straight lines in ptgui
Posted: 7 Feb 2012 at 15:32 GMT
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puppet warp in PS CS5 may be a good tool to correct misalignment.
Nick
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John Houghton
Posts: 3487
Location: Hitchin, United Kingdom
Registered: 17 Jan 2005
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Re: Straightening the straight lines in ptgui
Posted: 7 Feb 2012 at 18:09 GMT
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Nick, I would guess that most of the stitching problems can probably be eliminated by proper use of PTGui. Any remaining alignment errors could easily be dealt with in Photoshop, working with extracted rectilinear views. The transform tools offer all the facilities needed. But it's impossible to be sure without having a full set of images to investigate. We'll have to wait and see how Sonic fares with the 16mm Zenitar lens.
John
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