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Re: stitching of shots from the inside of a sphere

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  • Thomas
    Hugin actually assumes all input images are patches of a sphere seen from the inside (the panosphere, or sphere of vision) so should naturally do well at your
    Message 1 of 5 , Nov 19, 2012
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      Hugin actually assumes all input images are patches of a sphere seen from the inside (the panosphere, or sphere of vision) so should naturally do well at your job. It can be made to stitch flat mosaics, but I doubt it could ever handle a sphere seen from outside.

      I agree with Erik that the most important thing is plenty of overlap between images. Specifying that the source projection is spherical might be a good starting point, but the lens that took the pictures has to considered too. If it is rectilinear, then what you have is some rectilinear projections of patches of a sphere, and a rectilinear correction might give a less distorted final picture. Ideally you should calibrate the camera by taking a 360 degree set of pictures of something other than an eye, having plenty of local detail, with a 50% overlap between images. Align those with optimization of all lens parameters, and use the resulting correction parameters for stitching the eyeball images with lens optimization disabled.

      --- In PanoToolsNG@yahoogroups.com, Erik Krause <erik.krause@...> wrote:
      >
      > Am 16.11.2012 14:50, schrieb tderveaux:
      > > Examples:
      > > https://www.dropbox.com/sh/r1h70wmn4f5pfab/WGW6edwQjh
      > >
      > > How would I best feed these into panorama software? Other options of
      > > getting the best projection from the inside of a sphere are welcome of
      > > course.
      >
      > I'd use circular fisheye as input projection and allow for all lens
      > distortions to optimize. To get further help you should provide at least
      > two overlapping images (better all).
      >
      > --
      > Erik Krause
      > http://www.erik-krause.de
      >
    • Erik Krause
      ... I don t think this would help. One element of the lens is the eye itself, which you can t calibrate. Furthermore there most likely is non-symmetric
      Message 2 of 5 , Nov 19, 2012
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        Am 19.11.2012 18:07, schrieb Thomas:
        > Specifying that the source projection is spherical might be a good
        > starting point, but the lens that took the pictures has to considered
        > too. If it is rectilinear, then what you have is some rectilinear
        > projections of patches of a sphere, and a rectilinear correction
        > might give a less distorted final picture. Ideally you should
        > calibrate the camera by taking a 360 degree set of pictures of
        > something other than an eye, having plenty of local detail, with a
        > 50% overlap between images.

        I don't think this would help. One element of the "lens" is the eye
        itself, which you can't calibrate. Furthermore there most likely is
        non-symmetric distortion due to the different angles the ophtalmoscope
        (or fundus camera) is placed relative to the lens of the eye. So this
        images are not taken from the middle of the sphere, but from an opening
        in the sphere and with a "lens" where part of the lens elements are
        tilted relative to the others. All this would give a pretty non-uniform
        mapping.

        May be this could be corrected using mosaic mode (in hugin) respectively
        viewpoint correction (in PTGui). I guess a perfect fit would only be
        possible with morphing software.

        However, I would like to try on those images. Thierry, could you provide
        them?

        --
        Erik Krause
        http://www.erik-krause.de
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