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Add more constraints

PostPosted: Thu Mar 01, 2018 10:36 pm
by Roland Karlsson
Autopano is mainly based on automatic panorama detection and optimization. And this is very comfortable. You just insert your images, panoramas are detected, both lens distortion, focal length and the camera direction/rotation is optimized. This is very nice when it works and everything is just fine. Sure, you can do some manual stuff, but it is not easy and not always possible.

But, there are three problems, one huge and two smaller but annoying.

The huge one is that the tool can go totally wrong. It invents totally bogus distortion and focal length and then the directions are also off. Sometimes you do not even get a correct panorama, but often you do. But - the overlapping of the images are weird and detail at the edges are often skewed. This is what I think happens. The tool has a very difficult task and has problems. Then it starts to simplify the task by removing point pairs that do not match. But, the do not match because the tool is going in the wrong direction. And then, of course, the wrong way becomes the right way and the error amplified. And, the ironic thing is that the tool thinks that the mean deviation is low and show a green on the match. Just because it has itself removed all points that are in error. This problem is very difficult to fix. You can try different settings. But sometimes you have to take another image or use another lens.

The first small one is that, even if the tool gets a good overlapping of images, it is totally wrong regarding the horizon and the verticals. The image might meander like a snake. It is not easy to tame that snake. You can get it better quite easy. But to get it perfect is hard.

The second small one is areas with few points to find. It might even be cloud or leaf or water, that moves. Or it might be unsharp areas. Or dark areas.

All the above, IMHO, is due to lack of constraints. The tool wants to find an optimal solution to the optimization problem. But, sometimes this is not easy, or even possible.

So, what kind of constraints could we introduce to make it better.

1. The focal length given may be approximately right.
2. Lenses do not have certain kind of extreme distortions.
3. Sometimes we even know the lens distortion, or at least have a good opinion.
4. The image often contains verticals. Can that be used?
5. The images might have been taken with a panoramic head.
6. We might even know (or deduce) the angles used in the panoramic head.

With all those constraints, I do believe that Autopano will be a substantially improved tool.

Re: Add more constraints

PostPosted: Sat Mar 03, 2018 4:04 pm
by Roland Karlsson
I just made three panoramas. I used a fish eye lens, at F11 and exactly the same focusing. I took one row of 8 pictures, in portrait mode, i.e. 45 degrees. It was a very good overlap. I used distortion optimization for K3, which I have found almost always is a good idea. The three images were taken in my living room, my work rom and my big bath room. The one in the bath room worked very well. No real complaints. The other two had less success. Not very bad, but not good either. Switching around between the frames, things are moving, which hints at the distortion correction is wrong.

Looking at the distortion and focal length, they are very different for all three projects. I assume that, if I could import the bath room settings to the other two projects, then they would be much, much better. But, no such feature exists. Lets say that I might have touvhed the focus setting. Then the focal length and distortion would be slightly different. Then if the good panorama settings had worked as a constraint for the other two, then that would have been very valuable.