Phaser API Documentation

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Member of: Phaser.Geom.Polygon

<static> Earcut(data, [holeIndices], [dimensions])

Description:

This module implements a modified ear slicing algorithm, optimized by z-order curve hashing and extended to handle holes, twisted polygons, degeneracies and self-intersections in a way that doesn't guarantee correctness of triangulation, but attempts to always produce acceptable results for practical data.

Example:

const triangles = Phaser.Geom.Polygon.Earcut([10,0, 0,50, 60,60, 70,10]); // returns [1,0,3, 3,2,1]

Each group of three vertex indices in the resulting array forms a triangle.

// triangulating a polygon with a hole
earcut([0,0, 100,0, 100,100, 0,100,  20,20, 80,20, 80,80, 20,80], [4]);
// [3,0,4, 5,4,0, 3,4,7, 5,0,1, 2,3,7, 6,5,1, 2,7,6, 6,1,2]

// triangulating a polygon with 3d coords
earcut([10,0,1, 0,50,2, 60,60,3, 70,10,4], null, 3);
// [1,0,3, 3,2,1]

If you pass a single vertex as a hole, Earcut treats it as a Steiner point.

If your input is a multi-dimensional array (e.g. GeoJSON Polygon), you can convert it to the format expected by Earcut with Phaser.Geom.Polygon.Earcut.flatten:

var data = earcut.flatten(geojson.geometry.coordinates);
var triangles = earcut(data.vertices, data.holes, data.dimensions);

After getting a triangulation, you can verify its correctness with Phaser.Geom.Polygon.Earcut.deviation:

var deviation = earcut.deviation(vertices, holes, dimensions, triangles);

Returns the relative difference between the total area of triangles and the area of the input polygon. 0 means the triangulation is fully correct.

For more information see https://github.com/mapbox/earcut

Parameters:

name type arguments Default description
data Array.<number>

A flat array of vertex coordinate, like [x0,y0, x1,y1, x2,y2, ...]

holeIndices Array.<number> <optional>

An array of hole indices if any (e.g. [5, 8] for a 12-vertex input would mean one hole with vertices 5–7 and another with 8–11).

dimensions number <optional> 2

The number of coordinates per vertex in the input array (2 by default).

Returns:
Description:

An array of triangulated data.

Type:
  • Array.
Examples:
Since: 3.50.0
Source: src/geom/polygon/Earcut.js (Line 7)