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 and Description
protected static class	Tessellator.Node Circular Doubly-linked list used for polygon coordinates
static class	Tessellator.Triangle Triangle in the tessellated mesh

Method Summary

Modifier and Type	Method and Description
static 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 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)
static List<Tessellator.Triangle>	tessellate(XYPolygon polygon)

Methods inherited from class java.lang.Object

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

Method Detail

tessellate

public static final List<Tessellator.Triangle> tessellate(Polygon polygon)

tessellate

public static final List<Tessellator.Triangle> tessellate(XYPolygon polygon)

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)