Tuesday, September 6, 2016

A simple digital globe - 3

The digital globe program has been updated with the fix for the distortion where the left and right edges of the image meet when wrapped around the globe - where the "international date line" often is on a map of Earth.  It was simple bug, where one of the UV coordinates was being calculated based upon the wrong vertex.  Oops.  As you can see from the images below, though, I've fixed that, and updated the GitHub repository with the change.

The south polar region (Antarctica) on the map had enough detail it looks decent.  Alas, the northerly polar region was cut off above 80ยบ N, which is bit south of the northern edge of Greenland, Nunavut, and Svalbard - the resultant weirdness and distortion is plain to see.  This is something to consider when trying to apply many map projections like Mercator to the globe - the extreme latitudes may be cut off.  You might need to add some buffer space manually to resolve; you may also have to trim borders around the map.  The source image in this case was a Mercator-projection world map from Wikipedia.

There will probably be another post later, likely on a different topic.


A follow-up post on fixing the distortion can be found here.

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