stitching errors not seen in edit window  

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Phil Howard
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stitching errors not seen in edit window

by Phil Howard » Thu Jan 08, 2009 3:04 am

I am running into a stitching error similar to what sirwiz encountered. In my case I noticed that the stitching error is NOT visible in the edit window. But it shows up in the final result.

Here is what the edit window shows (200672 bytes, 1159x928):
http://phil.ipal.org/autopano/vance-pano/phil_vance-pano_img_1446_img_1469_24_9_edit-window-capture-1.png

Here is a typical result image (5729545 bytes, 5177x640):
http://phil.ipal.org/autopano/vance-pano/phil_vance-pano_img_1446_img_1469_24_9_5177x640_SCULS.png

The error appears on the right side in the 6th pew from the front. It can also be seen on the 7th and 8th pew. The 6th pew also has a 2nd split that does not extend to the 7th and 8th.

I notice the first split that runs through the 6th, 7th, and 8th pews extends to the door, but does not appear to be splitting the door. Maybe the noise in the dark door is confusing the software? Or maybe the perspective shift in the shadow of the garland decorations on the door and its frame is confusing the software?

I have encountered stitching errors like this before. But in previous cases, renderings in another image size did not show the error, so I didn't bring up the issue, and did not explore back to the edit window. But in the case of this church panorama, every size I rendered showed the same error. So that is why I looked back at the way the initial detection was done and saw that the edit window did not have the error.

Would the control points editor still be helpful in this case, even though the image in the edit window is coming out OK? I will be reading the documentation on control points editing tonight and giving that a try when I can.

All the files, including project and original images, are in the directory of the image URLs above, if someone wants to try it on their setup.

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leedsjoe
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by leedsjoe » Thu Jan 08, 2009 9:22 am

In 1.4.2 Edit | Settings you can see that, in Editor tab the blenders available do not include Smartblend but, under the Render Tab the default setting is Smartblend. This might account for the differences you report. (Multiband is available under both.)

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by marco-pano » Thu Jan 08, 2009 11:29 am

Hi Phil,
I just looked inside your .pano file. I see that you shot 24 pics at 15° in landscape mode with focale 29.2mm equiv35 in a single row. You have about 76% overlapping which is really useless, it's even bad as you have 79 links in the pano when 24 would be enough. All these long links between non adjacent pics lead to a bad stitching and some links have probably CPs just on the edge of pictures.

Shooting 10 or 12 steps in a row with landscape give enough overlapping. Or you could shoot 15 pics in portrait mode.

You can also see this nice video http://www.autopano.net/wiki/action/view/Manual_stitching_of_panoramas
to delete all the long links and keep only those between adjacent pics.
You can also try a new detection with half of the pics. Keep detection with strong algorythm. You can try with quality standard or high. If your lens is good quality, unselecting lens correction give sometime better result as sometime APP is correcting distortion a bit too much (advanced distortion is useless with standard lens).
Last edited by marco-pano on Thu Jan 08, 2009 11:30 am, edited 1 time in total.
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by mediavets » Thu Jan 08, 2009 11:31 am

Phil Howard wrote:Would the control points editor still be helpful in this case, even though the image in the edit window is coming out OK? I will be reading the documentation on control points editing tonight and giving that a try when I can.

Yes, this is a single row pano so each image needs only to be linked to its immediate neighbours.

Get rid of the superfluous links and re-optimise.

Video tutorial:
http://www.autopano.net/wiki/action/view/Manual_stitching_of_panoramas

You also have far too many images so you have excessive overlapping.

You will get sufficient overlap with fewer than half as many images.

I think 9 or 10 around should be sufficient with 16mm lens on a 1.6x crop Canon body in portrait orientation.

So with your current image set use every other shot, which will leave you with 12 images - more than enough.
Last edited by mediavets on Thu Jan 08, 2009 11:42 am, edited 1 time in total.
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Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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by mediavets » Thu Jan 08, 2009 12:05 pm

Phil,

I tried a stitch using every other image.

It is apparent that these images were not shot at regular yaw intervals.

I guess you did not use a click-stop pano head?

Perhaps you are using a standard tripod head rather than a pano head and estimating yaw intervals by eye?

If you are not using a proper pano head with camera/lens set at the NPP then you will get parallax errors - resulting in stitch errors in rendered pano - when shooting this sort of interior scene.

A proper pano head would also facilitate mounting the camera in a portrait orientation gving you a greater vertical FOV.
Last edited by mediavets on Thu Jan 08, 2009 12:10 pm, edited 1 time in total.
Andrew Stephens
Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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by mediavets » Thu Jan 08, 2009 2:19 pm

I have tried several different subsets of your images with extensive manual CP editing.

Prinicipally placing CPs on areas as far from the camera as possible.

But have failed to get a really good stitch.

I think your images probably have unresolvable parallax errors.
Andrew Stephens
Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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Phil Howard
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by Phil Howard » Thu Jan 08, 2009 4:12 pm

mediavets wrote:Phil,

I tried a stitch using every other image.

I tried that, too. It still produced errors. The one on the right 6th pew was not as severe, but was present. There were a number of other errors, although quite small. With all 24 images, those others were gone or too small for me to even see. I did it with the ODD images. I'll try again with the EVEN images and see how that goes.

mediavets wrote:It is apparent that these images were not shot at regular yaw intervals.

I guess you did not use a click-stop pano head?

Perhaps you are using a standard tripod head rather than a pano head and estimating yaw intervals by eye?

If you are not using a proper pano head with camera/lens set at the NPP then you will get parallax errors - resulting in stitch errors in rendered pano - when shooting this sort of interior scene.

A proper pano head would also facilitate mounting the camera in a portrait orientation gving you a greater vertical FOV.

It is a 3D head with 15 degree markings. The yaw error is the amount of error that results from manually adjusting the head to mate the markings visually. It should "accumulate" to 15 degree steps, but with jitter of maybe a degree or two.

I was considering cropping each of the 24 images to half width. But then, there would either be no EXIF data, or the data would not correctly represent the image.

If there were stitching errors all around the place, I could more easily understand the error involved. But with Smartblend, there is only that one severe one (6th to 8th pew) and the little one right next to it (6th pew only).

The head does allow me to get close to centering the entrance pupil. It's about 2cm in front of the center (e.g. the yaw axis runs up through the lens axis at about 2cm behind the entrance pupil).

I'm still looking for a pano head. I am looking first for one that mounts on my tripod in place of the head that is there now. So far, nothing found. The tripod to head mount may be proprietary to Bogen. I guess I should start looking for other mount heads. Any suggestions from what is sold at B&H (for now I buy everything from there).

I should also have shot that in portrait mode instead of landscape mode. But I had time pressure as the musicians were to start practice soon giving me only a 20 minute window to level the tripod on the slanted floor and make all the long exposures with the given lightning level. After that, people would be arriving for the Christmas church service. Otherwise I would have shot 72 images at 5 degree steps knowing I can always throw away any excess and try the stitching with whatever interval worked OK. For example, maybe every 20 degrees would have worked best (but I can't do that now). I have done 5 degree (visually estimating 1/3 of the 15 degree marks) and those stitches came out fine. But that was done with much better lightning and more details. I've also done 7.5 degree. All have been done on the same head, so there is always some jitter in the yaw positioning.

I did try doing a stitch by omitting just the ONE image that had the bad stitch on it's right edge. That sure came out in a mess. I guess it really needs some consistency to get a good stitch. If I could do some geometric distortion around that bad stitch point, I'm sure I could make it better. I can visualize in my head the distortion that would fix it (a partial quadrant rotation in 2 of the images there).

It would seem to me if I put control points along the edges of the pews, that should at least get things closer. But those are relative smooth parts of the image so I assume automatic control points would not be placed there.

Are those videos available as straight video files? Flash won't run on my browser (due to a multi-process mode in the browser, the Flash installer gets confused). If the video is on Youtube, then I can view it there (those are directly downloadable in most of the formats found there).

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by Phil Howard » Thu Jan 08, 2009 4:33 pm

marco-pano wrote:Hi Phil,
I just looked inside your .pano file. I see that you shot 24 pics at 15° in landscape mode with focale 29.2mm equiv35 in a single row. You have about 76% overlapping which is really useless, it's even bad as you have 79 links in the pano when 24 would be enough. All these long links between non adjacent pics lead to a bad stitching and some links have probably CPs just on the edge of pictures.

Shooting 10 or 12 steps in a row with landscape give enough overlapping. Or you could shoot 15 pics in portrait mode.

You can also see this nice video http://www.autopano.net/wiki/action/view/Manual_stitching_of_panoramas
to delete all the long links and keep only those between adjacent pics.
You can also try a new detection with half of the pics. Keep detection with strong algorythm. You can try with quality standard or high. If your lens is good quality, unselecting lens correction give sometime better result as sometime APP is correcting distortion a bit too much (advanced distortion is useless with standard lens).

I did a stitch with the ODD images and it improved on the bad spot from before, but a number of other errors started showing, although they were not as severe. I should try with the EVEN set and see what that does. I wish I had the shooting time to do a portrait orientation. The Christmas decorations are now gone, so if I re-shoot, it's not the same thing. So I want to spend some time to try to make this one work.

If there was a feature that allowed me to mask the images such that I can specify parts of the image to not use for stitching, that might be useful, too. But I will proceed to learn how to do manual control points. Before I found Autopano, I was literally thinking of writing my own program to do stitching. If I had, it would have been very much like doing manual control points, using all triangular tessellation (so it would have been necessary to make control points form the points of all the triangles, rather than just links).

I'll try without the lens correction. The lens is the cheap kit lens (18mm-55mm) that came with the Canon 450D/XSi. I'll also try piping the images through a conversion that removes EXIF data. I've always wanted to know how Autopano does when it has no data but the images themselves. If it can work with that, then my next step would be to crop off the sides of these 24 images so they look more like portraits from a longer lens.

Is there an alternate source for the videos? Flash won't install in my browser due to another feature that has been added to it. If the videos are on Youtube, I could download them from there.

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by mediavets » Thu Jan 08, 2009 4:43 pm

Phil

Shooting more images that necessary results in excessive overlaps which will cause even more problems when stitching - it will not ameliorate parallax problems, those can only be avoided by:

1. Having nothing much closer to the camera than about 100 metres.
or:
2. Using a proper pano head with camera/lens set at correct NPP, pretty much essential for interior panos.

The most popular pano heads seem to be the Nodal Ninja 3 and 5 series. I have a NN5L it's very good.

You have browser that won't run Flash? Why use it? What use is that?
Andrew Stephens
Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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by mediavets » Thu Jan 08, 2009 4:46 pm

I think if you gave up on trying to create a 360 and went for partail pano you'd get a reasonable result. Are those ranks of pews really that interesting?
Andrew Stephens
Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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by Phil Howard » Thu Jan 08, 2009 5:05 pm

mediavets wrote:Phil

Shooting more images that necessary results in excessive overlaps which will cause even more problems when stitching - it will not ameliorate parallax problems, those can only be avoided by:

1. Having nothing much closer to the camera than about 100 metres.
or:
2. Using a proper pano head with camera/lens set at correct NPP, pretty much essential for interior panos.

The most popular pano heads seem to be the Nodal Ninja 3 and 5 series. I have a NN5L it's very good.

I'd need a USA retailer that carries it.

mediavets wrote:You have browser that won't run Flash? Why use it? What use is that?

I'm sure it would run Flash if the installer would succeed in installing it. The catch is, Firefox is modified for jailed security (which is essential for safe browsing with a number of things, Flash being one of them). The problem is, the Flash installer fails to install anything this way. Everything else in the browser works OK (I haven't tried all the various plugins available since I don't have any need for them). Javascript works fine. Java works fine. I can access all web sites that don't use Flash or have a Flash bypass. I can view Youtube videos by downloading them first and playing them in mplayer (and this saves on bandwidth when I want to replay them). Maybe my option is to figure out where the video file URLs are for the referenced videos and modify the downloader to understand those.

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Phil Howard
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by Phil Howard » Thu Jan 08, 2009 5:14 pm

mediavets wrote:I think if you gave up on trying to create a 360 and went for partail pano you'd get a reasonable result. Are those ranks of pews really that interesting?

I have planned to do a 120, anyway. Presumably that should work since the front showed up fine in the 360.

I showed people the other 360's I did (such as one around my house done at 3AM via moonlight) running automatic pans via Javascript (software I'll eventually be releasing when I get all the bugs out and refine the interface to using it ... I don't want any buggy test version on the loose). Some asked me to do the same for the church sanctuary with the Christmas decorations in place. The ranks of pews would not be interesting. But the animation of the pan might be to some people.

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by mediavets » Thu Jan 08, 2009 5:33 pm

Here's partial - just 7 of your images. Cylindrical projection.

Still has a stitch error - but you could edit that with image editor?




Last edited by mediavets on Thu Jan 08, 2009 5:38 pm, edited 1 time in total.
Andrew Stephens
Many different Nodal Ninja and Agnos pano heads. Merlin/Panogear mount with Papywizard on Nokia Internet tablets.
Nikon D5100 and D40, Sigma 8mm f3.5 FE, Nikon 10.5mm FE, 35mm, 50mm, 18-55mm, 70-210mm. Promote control.

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by Phil Howard » Thu Jan 08, 2009 5:50 pm

mediavets wrote:Here's partial - just 7 of your images. Cylindrical projection.

Still has a stitch error - but you could edit that with image editor?

I guess I could edit that. I'm still learning all the parts of Autopano.

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by Phil Howard » Fri Jan 09, 2009 12:53 am

I now have a much improved stitching from the church sanctuary panorama. The way I achieved this was based on comments about the excessive overlapping, too many links, and links deep into the images instead of the edges. I took all the original images and cropped them down to just the 50% part right in the middle. So the 24 images that were 4272x2848 were cropped to 2136x2848 from the center of each image. This lost the EXIF data in the process. The result turned out not quite perfect, but reasonably well (for a newbie). I found 2 places with some slight errors. But they would probably not be noticed by the average person not looking for them. They were in the pews.

Here is one of the resultant images:
http://phil.ipal.org/autopano/vance-pano-15deg-2136wide/phil_vance-pano-15deg-2136wide_img_1446_img_1469_24_22_6800x800_SCULS.jpg

The whole project (cropped input images, pano file, and several results) is at:
http://phil.ipal.org/autopano/vance-pano-15deg-2136wide/

While I may still explore improving on this using techniques like control points which today I did not get around to trying, I am going to go ahead and use these results for the church, and also for testing my animated panning Javascript.

Thanks for all the responses and advice.


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