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Re: [PanoToolsNG] Re: Forcing verticals to stay vertical in PTGui -- How?

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  • Scott Witte
    John (with extra thanks to Dave and Erik), What you suggest is pretty much what I ended up doing. For anyone interested you can see a screen grab from PTGui s
    Message 1 of 5 , Aug 19, 2007
      John (with extra thanks to Dave and Erik),

      What you suggest is pretty much what I ended up doing. For anyone
      interested you can see a screen grab from PTGui's Panorama Editor here:
      <http://scottwitte.com/temp/MKE_SkylineV09_PTGui.jpg> It may give a
      better appreciation for how many shots I needed to stitch together and
      the potential for difficulties.

      The problem was that the helicopter, try as the pilot might, couldn't
      hold a precise position while I was shooting all the elements leading to
      significant parallax errors between images. When PTGui tried optimizing
      all the control points it ended up tipping many of the buildings to get
      the best overall fit. To make matters worse not only were the boats
      bobbing, there were several boats moving through the harbor leaving
      wakes that changed from one exposure to another.

      What I ended up doing was taking just the images from the background
      (the skyline). Using only their control points and optimizing only them.
      The result was a very nice, straight and square skyline. That makes
      sense because the building were relatively far off compared to the
      helicopter's gyrations so parallax errors were relatively minor.

      Next I locked those background images in place (unchecked all of them
      for yaw, pitch and roll in advance optimization). I then turned on those
      optimizations for all remaining images and used the control points for
      all images and optimized again. The skyline stayed put and through a
      combination of morphing, masking, Smartblend and Photoshop I got the
      foreground looking right.

      This was a lot of work but you should see the results. Another image
      from this series ended up as a 5x24 foot backlit mural. The sharpness
      and detail are quite gratifying to say the least.

      Thanks again for the help.


      John Houghton wrote:
      > --- In PanoToolsNG@yahoogroups.com, Scott Witte <scottwitte@...> wrote:
      >> Is there a way in PTGui to force verticals to be exactly vertical and
      >> stay that way, warping everything else to fit?
      > The short answer is no. You need to calibrate your lens by evaluating
      > lens parameters in ideal conditions. Use these parameters in your
      > project and place control points only on features far away, so that
      > parallax effects are avoided. Images can then be aligned to give a flat
      > horizon and the verticals should be vertical or near vertical.
      > Features (relatively) near to the camera will inevitably exhibit
      > parallax errors so there will be stitching errors. There are two
      > possibilites for correcting these: manually in Photoshop, or use the
      > morphing feature in PTStitcher, which drags the points marked for
      > morphing into exact alignment by distorting the images. I have used a
      > combination of these two methods, but it takes a lot of work to get a
      > really good result. Of course, a lot depends on how severe the
      > parallax errors are.
      > John

      Scott Witte
      www.scottwitte.com <http://www.scottwitte.com>

      Member, APA | Midwest

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