Function earcut

  • earcut(
        vertices: ArrayLike<number>,
        holes?: ArrayLike<number>,
        dimensions?: number,
    ): number[]

  • Triangulate an outline.

    Parameters

    • vertices: ArrayLike<number>

      A flat array of vertice coordinates like [x0,y0, x1,y1, x2,y2, ...].

    • Optionalholes: ArrayLike<number>

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

    • Optionaldimensions: number

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

    Returns number[]

    A flat array with each group of three numbers indexing a triangle in the vertices array.

    Example

    earcut([10,0, 0,50, 60,60, 70,10]); // returns [1,0,3, 3,2,1]

    Example

    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]

    Example

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

Properties

default

Methods

deviation flatten

Properties

default

default: EarcutStatic

Methods

deviation

  • deviation(
        vertices: ArrayLike<number>,
        holes: undefined | ArrayLike<number>,
        dimensions: number,
        triangles: ArrayLike<number>,
    ): number

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

    Parameters

    • vertices: ArrayLike<number>

      same as earcut

    • holes: undefined | ArrayLike<number>

      same as earcut

    • dimensions: number

      same as earcut

    • triangles: ArrayLike<number>

      see return value of earcut

    Returns number

    Example

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

flatten

  • flatten(
        data: ArrayLike<ArrayLike<ArrayLike<number>>>,
    ): { dimensions: number; holes: number[]; vertices: number[] }

  • Transforms multi-dimensional array (e.g. GeoJSON Polygon) into the format expected by earcut.

    Parameters

    • data: ArrayLike<ArrayLike<ArrayLike<number>>>

      Arrays of rings, with the first being the outline and the rest holes. A ring is an array points, each point being an array of numbers.

    Returns { dimensions: number; holes: number[]; vertices: number[] }

    Example

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

    Example

    Transforming simple triangle with hole:
        const data = earcut.flatten([[[0, 0], [100, 0], [0, 100]], [[10, 10], [0, 10], [10, 0]]]);
        const triangles = earcut(data.vertices, data.holes, data.dimensions);

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