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https://issues.apache.org/jira/browse/LUCENE-8080?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Ignacio Vera updated LUCENE-8080:
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    Attachment: LUCENE-8080.patch

> GeoExactCircle improvement
> --------------------------
>
>                 Key: LUCENE-8080
>                 URL: https://issues.apache.org/jira/browse/LUCENE-8080
>             Project: Lucene - Core
>          Issue Type: Improvement
>          Components: modules/spatial3d
>            Reporter: Ignacio Vera
>            Assignee: Karl Wright
>         Attachments: LUCENE-8080-test.patch, LUCENE-8080.patch
>
>
> Hi [~daddywri],
> Current implementation of GeoExactCircle seems to work well for planet models 
> with low flattening (~|0.025|). When flattening increase shapes start 
> becoming invalid because of the cutting angle of the circle plane which 
> results on the center of the circle ending up on the wrong side of the plane. 
> I propose a new version of GeoExactCircle that tries to overcome this problem 
> by creating a new plane for a circle sector in such cases. The new plane is 
> built built for each sector when needed by using two points from the circle 
> edge and the center of the world. The plane is such that it is built as close 
> as possible to the circle plane of the sector. Points from the circle plane 
> must not be within the new plane and the center of the circle must be within 
> the plane.
> This approach seems to work well up to planets with flattening up to around 
> ~|0.1|. I think after that the cutting angles of circle planes can be so thin 
> that the apporach is not valid. 
> Therefore I propose to add this new approach and limit the creation of such 
> circles to planet models with flattening lower than |0.1|. Probably a 
> limitation that does not affect most of the realistic cases.
> In addition this new version forces a minimum of 4 sectors in a circle. The 
> issue on LUCENE-8071 came up again for circles of any radius so we should 
> enforce it for all circles.
> Thanks!



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