Package org.apache.lucene.geo

Class Tessellator

java.lang.Object
org.apache.lucene.geo.Tessellator
public final class Tessellator extends Object
Computes a triangular mesh tessellation for a given polygon.

This is inspired by mapbox's earcut algorithm (https://github.com/mapbox/earcut) which is a modification to FIST (https://www.cosy.sbg.ac.at/~held/projects/triang/triang.html) written by Martin Held, and ear clipping (https://www.geometrictools.com/Documentation/TriangulationByEarClipping.pdf) written by David Eberly.

Notes:

  • Requires valid polygons:
    • No self intersections
    • Holes may only touch at one vertex
    • Polygon must have an area (e.g., no "line" boxes)
    • sensitive to overflow (e.g, subatomic values such as E-200 can cause unexpected behavior)

The code is a modified version of the javascript implementation provided by MapBox under the following license:

ISC License

Copyright (c) 2016, Mapbox

Permission to use, copy, modify, and/or distribute this software for any purpose with or without fee is hereby granted, provided that the above copyright notice and this permission notice appear in all copies.

THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES WITH' REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected static class 
    Tessellator.Node
    Circular Doubly-linked list used for polygon coordinates
    static final class 
    Tessellator.Triangle
    Triangle in the tessellated mesh

  • Method Summary

    Modifier and Type
    Method
    Description
    static final boolean
    linesIntersect(double aX0, double aY0, double aX1, double aY1, double bX0, double bY0, double bX1, double bY1)
    Determines whether two line segments intersect.
    static final boolean
    pointInPolygon(List<Tessellator.Triangle> tessellation, double lat, double lon)
    Brute force compute if a point is in the polygon by traversing entire triangulation todo: speed this up using either binary tree or prefix coding (filtering by bounding box of triangle)
    static boolean
    pointInTriangle(double x, double y, double ax, double ay, double bx, double by, double cx, double cy)
    compute whether the given x, y point is in a triangle; uses the winding order method
    static List<Tessellator.Triangle>
    tessellate(Polygon polygon, boolean checkSelfIntersections)
     
    static List<Tessellator.Triangle>
    tessellate(XYPolygon polygon, boolean checkSelfIntersections)
     

    Methods inherited from class java.lang.Object

    clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • tessellate

      public static List<Tessellator.Triangle> tessellate(Polygon polygon, boolean checkSelfIntersections)

    • tessellate

      public static List<Tessellator.Triangle> tessellate(XYPolygon polygon, boolean checkSelfIntersections)

    • linesIntersect

      public static final boolean linesIntersect(double aX0, double aY0, double aX1, double aY1, double bX0, double bY0, double bX1, double bY1)
      Determines whether two line segments intersect. *

    • pointInTriangle

      public static boolean pointInTriangle(double x, double y, double ax, double ay, double bx, double by, double cx, double cy)
      compute whether the given x, y point is in a triangle; uses the winding order method

    • pointInPolygon

      public static final boolean pointInPolygon(List<Tessellator.Triangle> tessellation, double lat, double lon)
      Brute force compute if a point is in the polygon by traversing entire triangulation todo: speed this up using either binary tree or prefix coding (filtering by bounding box of triangle)