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https://issues.apache.org/jira/browse/LUCENE-8220?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16412583#comment-16412583
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Karl Wright commented on LUCENE-8220:
-------------------------------------
I solved the tiling issue successfully, but then we wind up with the attempted
construction of a concave polygon with all colinear points. That's essentially
saying that it wants to include either half of, or all of, the world -- which
in this case may make sense. I have to analyze the situation more completely
later today to see what it's trying to do.
For the record, the tiling fix is simple. The code in question looks for edge
sidedness violations that would preclude use of a GeoConcavePolygon. It used
to take the first such detection and generate a triangle and two other sections
from that. Now, it attempts to do that, but if it fails, it just continues
looking for another violation. Only if it finds violations and can't find a
way to address them does it throw an IllegalArgumentException. I believe this
will always work because violations always come in pairs. We'll see.
> GeoPolygon factory still shows problems with coplanar points
> ------------------------------------------------------------
>
> Key: LUCENE-8220
> URL: https://issues.apache.org/jira/browse/LUCENE-8220
> Project: Lucene - Core
> Issue Type: Bug
> Components: modules/spatial3d
> Reporter: Ignacio Vera
> Assignee: Karl Wright
> Priority: Major
> Attachments: concave.jpg, concaveWithTiling.jpg,
> coplanarity-test.patch
>
>
> The attached patch contains two polygons that still shows problems with
> co-planar points. To better explain the issue I attached some images:
> 1) concave.jpg: This is the polygon we want to build. Note that we want to
> build the concave part, therefore the blue part is actually not part of the
> shape and the white part is the area cover by the shape.
> 2) concaveWithTiling.jpg: The algorithm of the polygon factory tries to tile
> the polygon using convex polygons. In our case it creates the three colored
> polygons on the image. What it remains is a concave polygon.
> The problem with this polygon is that the right edge of the concave polygon
> contains co-planar points. These points cannot be merged into a single plane
> because they have different properties (internal edges or shape edges).
> Because GeoConvexPolygon and GeoConcavePolygon cannot handle polygons with
> co-planar points, the polygon cannot be built.
> [~kwri...@metacarta.com], Is it possible to make this polygons support such
> an extreme case?
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