Hi Tom,
Tom Sharpless wrote: > Did your calibration image set cover 360 degrees? No, this was a a-b-c calibration only. I left the FOV fixed > It seems to me that if you use multiple images for calibration, then > the correct focal length or fov becomes a critical parameter (which is > not the case for single-image straight line calibration). And it is > known that the PT optimizer will almost always choose a wrong value > for that unless you force it to be right by insisting on closure of a > full circular image set. Hmm, good point. I didn't check if a (small) change in the FOV results in different a-b-c, but it seems somewhat reasonable. > But the straight line control point optimization (as currently > implemented) requires that the output projection be rectilinear. So > naively I would suppose that only a part of your straight line data > would be usable, unless the rectilinear error is computed separately > for each image, ignoring the rotation that aligns it on the > panosphere? Yes. I kept all images at yaw/pitch/roll=0 and thus had a maze of lines within the FOV and requested each of the lines to be straight in the output... > Some time ago I looked into the possibility of making libpano optimize > straight lines on the panosphere (where they become great circles) > instead of in a rectilinear projection. Yes, I remember. > My hope was to better support calibration of fish eye lenses, which is a > continuing problem. My code gave worse results than the existing method, so > I gave it up. I guess the reason is that in your method it strongly depends on the correct location of the image (y,p,r), isn't it? So it would be a good thing for panoramas in general, but meybe less for calibration only? > However I still think Hugin needs an easy and reliable way to do > straight line lens calibration. I believe that after many years of > using various calibration systems, photogrammetrists finally decided > the straight line method was best. And they often use naturally > occurring straight lines rather than special calibration rigs. The > key is software that can follow lines and estimate their positions to > subpixel accuracy. The raw image of a calibration line will in > general be curved, so a human has to designate which lines are > straight in reality -- but not set dozens of control points on them. Hmm, indeed. an automatic line finding algorithm might be a handy thing. Sounds like calling for Hough transforms or alike. But for fisheye images that really must be an awkward job... Cheers, Pit -- Dr. Peter "Pit" Suetterlin http://www.astro.su.se/~pit Institute for Solar Physics Tel.: +34 922 405 590 (Spain) p.suetter...@royac.iac.es +46 8 5537 8534 (Sweden) peter.suetter...@astro.su.se --~--~---------~--~----~------------~-------~--~----~ 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 -~----------~----~----~----~------~----~------~--~---
