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Sep 10, 2017, 07:20 PM
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Dual fish to sphere equations


After many days of searching, a legit looking source appeared.

http://paulbourke.net/dome/dualfish2sphere/

http://paulbourke.net/dome/fish2/#fish2pano


Of course, like most things these days, there's no source code for a complete converter. There's just enough source code to develop a converter from scratch. More clues come from a list of command line arguments required to stitch the images.


Using standard image processing techniques, the equations finally yielded a proper equirectangular projection. Without the benefit of automated control points, a lot of manual tweeking got the horizons to line up, but failed to align anything above or below. It definitely wasn't parallax distortion. The right eye needed to be rotated in the opposite direction for the bottom to line up. It would be impossible to align the images without a GUI giving instant feedback.


The field of view can be adjusted by getting objects on the horizon to line up horizontally. It's not clear how to adjust the radius. The center XY parameters he provided are the input coordinates of the fisheye. He then provided XYZ rotation parameters which appeared to transform the input coordinates. Because the rotation & center parameters feed back into each other, it was impossible to get very far that way.


It was easier to make the X & Y rotation apply to the output & make center X & Y where to capture the input. Z rotation still worked by transforming the input coordinates.


The next step would be finding a decent viewer besides the goo tubes. Lions prefer watching spherical videos as equirectangular projections, but there's no way to know if the projection works without a viewer. There's also a new class of effects which apply just to spherical video.
Last edited by Jack Crossfire; Sep 10, 2017 at 10:14 PM.
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