This module implements a modified ear slicing algorithm, optimized by zorder curve hashing and extended to handle holes, twisted polygons, degeneracies and selfintersections 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 multidimensional 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
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 12vertex 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). 
An array of triangulated data.