Categories: Panorama art & techniques: :

Align Symmetry Pano

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Align Symmetry Pano Joseph Foo Chean Hsu 9/18/12 11:15 PM
Hi all, I had taken a shot on this location which look symmetry. and when I put it in PTGui, it seems like PTGui is been confused by the symmetry image. I tried to manually fix some control point, it still won't work, because once I align again, the "confused control point" will be added in again, and then I manually delete again, and it goes on and on and on...
I very confident that there's nothing wrong with my image, cause I'm using 8mm fisheye and shot 8 shot vertical and one up one down.

So it's there any trick that I need to do to make sure PTGui doesn't get confused? 

Thanks a lot.
Joseph Foo Chean Hsu
Re: Align Symmetry Pano Igor Adamec 9/19/12 1:44 AM
I had a similar problem with one of my panoramas. If I recall correct, the solution is, after adding control points, not to start 'alignment', but to run 'optimization'. You can find it if you click on 'Advanced>>' button at the upper right corner of the 'Project Assistent' tab.
Re: Align Symmetry Pano Calvin McDonald 9/19/12 8:15 AM
Joseph:

It has been my experience that auto generated CPs are often wrong in images with large amounts of symmetry.  I too have experience this - for example, with this image:  http://www.360cities.net/image/idaho-state-capital-center-rotunda#-44.21,-90.00,105.8

After going through the "on and on and on" thing you referred to, I finally removed all auto CPs and created a small set of manual CPs and had much better success.

Also, I'm not positive about this but I believe that Alignment will only auto insert CPs if there are image boundaries without CPs.  If all images have at least one CP to adjacent images I don't think it will attempt to insert any auto CPs.  Maybe someone else can comment if I'm correct or not.  And as Igor stated, you don't have to run Alignment.  Just make sure the CPs are correct, which with a symmetric image can be hard when doing it manually also, and build.

Calvin

Re: Align Symmetry Pano HighDesertView 9/19/12 5:06 PM
After my first few 360s, I stopped using the "Align" button and went to the advanced mode.  However, I know of other photographers who have good results with the automated Align option.

Going into the advanced mode doesn't mean that you have to place all the control points yourself.  You can select the two images in the control point window and then try Control-Shift-G to generate control points for those those two images.  I do this for all my adjacent photos, so I'm not running PTGui fully automatically (I don't push the Align button), but I do let PTGui handle control point placement between two images.

Once you have the number of control points you want between your adjacent images, then Use the Optimizer tab to "Run Optimizer".  I get a bit more fancy than this and enter the advanced mode in Optimizer, but you may get good enough results with the standard Run Optimizer.

FYI, you can also try linking all photos at once with Control-Alt-G.  This will try to identify control points in ALL photos, but will NOT run the optimizer.  Essentially this is what you get with the Alignment button but without actually aligning the photos.  You could then look for the trouble control points and delete them before running the Optimizer.

John.
Align Symmetry Pano Lastwolf 9/19/12 6:41 PM
Hi Joseph,

One trick I use in PTGui is to look at the control point table and sort them by distance. I'll then select and delete all control points with a distance greater than say 15. This normally gets rid of any mis aligned control points and gives me a good or very good result after running the optimizer. If that still doesn't work I will go through each overlapping set of images and inspect each cp looking for the culprit.  One other trick I use, especially when shooting a location with a symmetrical floor, is to throw a piece of paper or some other small object on the floor to give me a point of reference. I can then remove it in post.

HTH.

Rich

Re: Align Symmetry Pano HighDesertView 9/19/12 8:42 PM
PTGui will also throw out "bad" control points that fall way outside the average separation.  Control+Shift+W.  Sometimes it's useful to generate more control points than you need (between two images: Control+Shift+G, or all images: Control+Alt+G).  Most will be good and help PTGui better determine the bad ones to throw out when you press Control+Shift+W.

I run the Control+Shift+W a few times until PTGui doesn't find any more "bad" CP and then manually do the same thing Joseph suggests: sort by distance and look at the worst ones myself (double click on the CP in the sorted list to pull up the two images automatically).
Re: Align Symmetry Pano Joseph Foo Chean Hsu 9/24/12 11:28 PM
Hi, thanks for all of you. It's really helpful. and my problem solved! XD