On 22 Jan., 22:20, Pablo d'Angelo <pablo.dang...@web.de> wrote:
> I have thus implemented a new RANSAC model that can make use of the > restrictions we have in panoramas, and also include prior information > about lens type, HFOV and distortion etc. Basically, it tries to > estimate roll,pitch and yaw for each image pair (using two control > points), and checks if the remaining points are consistent, and repeats > that a few times. This is definitely the way to go. Since RANSAC bases it's exclusion of outliers on a consistency check which depends on feedback from a model, if the model is wrong (i. e. assuming rectilinear images) consistency of a set of points under consideration cannot be established. Extending the tolerances here will only gloss over the fact that the model is wrong, not the points fed into it. There is no way to avoid having information about FOV and projection - if the EXIF data don't yield, the user must provide. > Unfortunately, in some cases, the HFOV is not know very well (incomplete > EXIF data, bad crop factors entered by the user etc...), so one cannot > unconditionally recommend --ransacmode rpy. You have to draw the line somewhere. If the EXIF data are missing and the user is prompted to supply sufficient subset of FOV, crop factor and focal length and the user enters wrong data, you can't make it right for him/her. What the user can do if he/she has no clue at all is do a panorama as best as they can and so arrive at an estimate of these data to use from then on. > 1. User has a good estimate of the HFOV (EXIF Data or prior > calibrations) -> use cpfind --ransacmode rpy > which makes cpfind virtually bullet proof to really bad mismatches. > > 2. Bad EXIF Data and user doesn't know about crop factors or the like -> > use cpfind --ransacmode auto (the default) or cpfind --ransacmode > homography, and accept some outliers. I think that is a perfectly reasonable choice. And once case 2 has produced a roughly correct output, the FOV has been established with sufficient accuracy to use --ransacmode rpy. > I hesitate to default to --ransacmode rpy, as this will probably lead to > quite some breakage for novice users, who enter bad crop factors. quite right. I'd assume the inexperienced users aren't usually the ones using fisheyes anyway. > I find 2. a bit unsatisfying as it means that we will get suboptimal > results for many inexperience users (and many experienced ones too, who > don't know about all the cpfind internals...). > > Whats your opinion about that? I feel that the problem here is in the presentation of these choices. As long as the user, experienced or not, has to make all the way into the CPG settings dialog to modify command line arguments, all but the most confident and experienced users will hesitate to go down that road. The treatment of CPGs, CPG parameters and their manipulation needs a facelift. The capabilities of the CPGs themselves, be it your creature cpfind or the other, patent-encumbered ones, are, imho, perfectly sufficient. > - Try to automatically add --ransacmode rpy, if the hugin could > successfully read HFOV from the EXIF data? In theory this is a fine idea. But keep in mind one point that noone ever adresses in this whole discussion: The treatment of FOV in hugin is, if I am interpreting the mechanism right, fundamentally flawed. The only thing that is asked for and processed seems to be the HORIZONTAL field of view. Now if I make images with an APSC sensor and, in landscape mode, have a HFOV of 60 degrees, then do some shots in portrait, suddenly the HFOV is 40 degrees. Hugin even insists on me entering a 'different lens' instead of just calculating the diagonal fov and realizing it's the same thing after all. So a 60 degree limit does not necessarily work - if hfov in landcape is, say, 65 (like with my ordinary zoom lens at 18mm) and 43 in portait, all of the sudden the same lens would once be treated as a fisheye and once as a rectilinear. Please correct me if I'm mistaken. Kay -- You received this message because you are subscribed to the Google Groups "Hugin and other free panoramic software" group. A list of frequently asked questions is available at: http://wiki.panotools.org/Hugin_FAQ To post to this group, send email to hugin-ptx@googlegroups.com To unsubscribe from this group, send email to hugin-ptx+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/hugin-ptx
