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Re: 360 Gopro 3D crowd

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  • panovrx
    Here from the Gopro Users 3D forum are some answers I made to questions about Gopro 3d panorama production ... ... (camera stuff) This is stitched (with PTGui)
    Message 1 of 2 , Nov 20, 2012
      Here from the Gopro Users 3D forum are some answers I made to questions about Gopro 3d panorama production

      >> http://www.mediavr.com/newtown3d/newtown3dgopropanorama.htm
      (camera stuff)
      This is stitched (with PTGui) from 10 seconds worth of video frames --
      with the 3d kit (with an extender) with Hero 2s with Protune, 1080p M, 25 fps -- with the
      cameras on a pole with a rotator which is spinning them around at 1 revolution in 10 seconds
      -- what look like sync errors are in fact blending differences of the stitching of the action on the L and R images

      (stitching stuff)
      The work flow is convoluted but fast because the frames are small.
      Calibration means finding common points between images and working out how the camera must have
      rotated between shots and what kind of lens characteristics it must have (fov, distortions,off-centeredness).
      The common points are found automatically and the point finding can be constrained by masks allowing
      you to specify that only static and distant points are used in some calibration situations

      First I crop the videos to synced 360 sequences and convert to frames (L and R sets).
      Then stitch the R frames with PTGui -- because my rig rotates around the R camera lens axis.
      And level the panorama it will produce in PTGui. Now we know the orientation of frame 1 of the R sequence
      Then I work out the orientation of the first frame of the L sequence by using distant
      common points with frame 1 of the R sequence.
      Then I convert all the R fisheye frames into narrow equirectangular format images 150 degrees high, 40 degrees wide using the first R frame orientation for all frames.
      Then ditto I convert all the L fisheyes into narrow equirectangular format images 150 degrees high, 40 degrees wide using the first L frame orientation for all frames.
      Each of these pairs of R and L equi frames are parallel to each other and could make aligned stereo pairs with no further work.
      Then I stitch the R equi frames into a panorama (the R panorama) using a fresh calibration. Save that calibration as a template and apply it to the L equi frames to get the L panorama.


      (viewer stuff)
      PTGui will output a webpage with an interactive Flash panorama. More specialised
      authoring packages like Pano2VR and Panotour Pro can deliver versions that work on mobile
      devices and tablets too -- using sensors in the devices sometimes to provide a more
      intuitive interface. Eg -- turn your Iphone and you see the panorama scroll realistically.
      I use Panotour Pro for these panoramas but Pano2VR has some specific advantages for anaglyph stereo
      panoramas (better no color compression workflows).

      If you look at the street panorama -- in non-interactive form
      you can see that the vertical alignment of L and R views is accurate

      but if you look at the festival panorama -- in interactive form
      you will see that there is a lot of vertical misalignment in some parts of the image

      This is not because the festival panorama had vertical misalignment in the non-interactive form.
      It is a more fundamental problem to do with how capturing a stereo panorama this way is not
      equivalent exactly to turning around and looking up and down in the real world with two eyes.

      But you will notice the vertical alignment is good in a vertical zone in the center of the viewer.
      And if you dont mind strong disparities in the rest of the image it still gives a strong 3d impression.

      You will notice too that if you tilt down the bottom corners of the images have the worst disparities.

      This is the main problem for stereo panoramas done with two spinning cameras -- getting all-over vertical
      alignment in interactive versions.

      If you use DSLRs you can get much sharper stereo panoramas done the same way but the Gopros are
      rapidly getting towards that sort of quality and are much faster and more flexible in the kind of stereo panoramas
      you can make with them
      but the viewer view alignment issues remain

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