fix mitering bug with ground polylines over long distances #7885
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Thanks for the pull request @likangning93!
Reviewers, don't forget to make sure that:
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That fixes our issue. Thanks! |
likangning93
commented
May 31, 2019
| var vertexUpScratch = new Cartesian3(); | ||
| var cosine90 = 0.0; | ||
| var cosine180 = -1.0; |
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@lilleyse for context, computeVertexMiterNormal is meant to compute a normal pointing to the "right" side of a join between two line segments defined by 3 points, eventually this is used to compute normals on the start and end faces of the volumes around polyline segments.
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Looks good! |
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Fixes #7855.
GroundPolylineGeometrymiters between line segments, but only if their endpoints aren't coplanar.This used to be a literal coplanar check, but this would fail sometimes for very long-distance line segments due to the tiny epsilon used for coplanarity. The computed miter vector would then also have problems due to the curvature of the Earth, since it was a naive average of the directions from point-to-point.
This PR moves the check for whether miters are needed or not to a check using vectors pointing towards the segments' end points but tangent to the surface of the ellipsoid.
The spec for miter breaking was also incorrect, the first test case wasn't even encountering a miter break.