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Posted to issues@commons.apache.org by "Baljit Singh (Jira)" <ji...@apache.org> on 2019/12/20 21:10:00 UTC

[jira] [Created] (MATH-1507) Barycenter of a clockwise SphericalPolygonsSet is incorrect.

Baljit Singh created MATH-1507:
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             Summary: Barycenter of a clockwise SphericalPolygonsSet is incorrect.
                 Key: MATH-1507
                 URL: https://issues.apache.org/jira/browse/MATH-1507
             Project: Commons Math
          Issue Type: Bug
    Affects Versions: 3.6.1
            Reporter: Baljit Singh


Let's say there is a circle on a spherical surface.
 * The circle center is given by S2Point(theta=-0.6981, phi=0.87266). The radius is irrelevant.
 * Let's discretize this circle into a polygon with 100 edges. Let's make the orientation {color:#FF0000}clockwise{color}.
 * Since its a clockwise circle, from symmetry, we know that the barycenter would be around S2Point(theta=2.44346, phi=2.268928), which is just the reverse of the normal vector at the circle center.
 * Using SphericalPolygonsSet, the calculated barycenter is S2Point(theta=2.4922, phi=0.69889).

 

A few things I've already tested:
 * For counterclockwise, the result is correct.
 * The perimeter and surface area of the polygon is correct for both counterclockwise and clockwise.

 

 

 

 



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