earcut 1.1.5

A pure Python port of the earcut JS triangulation library

earcut-python

A pure Python port of the earcut JavaScript triangulation library.

The latest version is based off of the earcut 2.1.1 release, and there have been following enhancements:

• if dimensions == 2, project data into 2D instead of triangulating only first two coordinates

The original project can be found here: https://github.com/mapbox/earcut

Pypi

Available on pypi.org

pip install earcut

Usage

triangles = earcut([10,0, 0,50, 60,60, 70,10]) # Returns [1,0,3, 3,2,1]

Signature: earcut(vertices[, holes, dimensions = 2]).

• vertices is a flat array of vertex coordinates like [x0,y0, x1,y1, x2,y2, ...].
• holes is 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 is the number of coordinates per vertex in the input array (2 by default).

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, you can convert it to the format expected by Earcut with earcut.flatten:

# The first sequence of vertices is treated as the outer hull, the following sequneces are treated as holes.
data = earcut.flatten([[(0,0), (100,0), (100,100), (0,100)], [(20,20), (80,20), (80,80), (20,80)]])
triangles = earcut(data['vertices'], data['holes'], data['dimensions'])

After getting a triangulation, you can verify its correctness with earcut.deviation:

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.