From: Thomas S. <tks...@gm...> - 2010-02-09 14:02:23
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My 2 cents Why don't we start using focal length rather than FOV as the basic angular scale parameter? It is a pure scale factor, independent of image size and the shape of the projection function, both of which are conflated in FOV. In my experience, 3/4 of the confusion about image scaling and angle-of-view calculations comes from the difficulty of disentangling those 3 basic parameters from FOV. Regards, Tom 2010/2/9 Pablo d'Angelo <pab...@we...> > > Hi all, > > I believe that this needs to be moved to panotools-devel or hugin-ptx. > Is everybody ok with this? I will then repost on these lists. > > D M German wrote: > >> Hi Pablo, >> >> One of problems I encountered when trying to do very long mosaics of a >> wall, is that I had to "fake" the FOV of each photo to be very small. >> >> Also, another problem of libpano is that horizontal/vertical shift is >> done before the image is mapped to the panosphere (and before the lens >> correction is done). But for plannar mosaics you want to do the >> translation after the image has been mapped to the infinite plane. >> > > Actually, this shift is a part of the lens correction and not designed for > a planar mode. This is why an additional shift at the right place would be > much better. > > Pablo> They are the normal FOV of the camera that was used for capturing >> the >> Pablo> image. This also means that all the distortion correction >> mechanisms >> Pablo> etc. still work properly, and one can reuse the lens calibration >> for >> Pablo> all images that were captured with the same camera (and optimize >> them >> Pablo> jointly). >> >> This was the main motivation of the plannar mode. >> > > Then I don't see why it is necessary to make such intrusive changes. > > If the panorama projection is set to rectilinear, the panorama will be > identical to the image on the plane, and one basically gets a planar mode > for free. It is not very useful with the default r,p,y parameters, though. > This is why I added the Tr ones. > > I just saw that the optimizer always minimizes distances on the sphere and > not in the output image. While this might makes sense for the panoramic > usecase, it is probably not desirable for creating a planar mosaic. > > > One does not have to > >> fake extremely narrow FOV for the lens to fit the mosaic in a sphere >> (although, from what you say Pablo, the image will just keep wrapping >> around the sphere several times). >> > > No, that is not possible with a rectilinear panorama anyway. > > > By having a plannar mode we can use > >> the proper FOV of the lens. >> > > Actually, this is also possible with the Tr parameters. > > However, I found that with the additional parameters, optimisation > generally tends to become more unstable, and I'm not sure if the Tr or a > modified Ti (as used by PTGui and PTStitcherNG) is better in that respect. > > ciao > Pablo > > > > ------------------------------------------------------------------------------ > The Planet: dedicated and managed hosting, cloud storage, colocation > Stay online with enterprise data centers and the best network in the > business > Choose flexible plans and management services without long-term contracts > Personal 24x7 support from experience hosting pros just a phone call away. > http://p.sf.net/sfu/theplanet-com > _______________________________________________ > PanoTools-devel mailing list > Pan...@li... > https://lists.sourceforge.net/lists/listinfo/panotools-devel > > |