mapbox-earcut

import numpy as np from mapbox_earcut import earcut # Define a polygon with an outer ring and an inner hole # Vertices are flat: [x0, y0, x1, y1, ...] # Outer ring (0-3): [10,0], [0,50], [60,60], [70,10] # Hole (4-7): [30,10], [30,30], [20,20], [20,10] # The hole_indices array specifies where each hole's vertices start in the `data` array. data = np.array([ [10,0], [0,50], [60,60], [70,10], [30,10], [30,30], [20,20], [20,10] ]).flatten() # Earcut expects a flat array of coordinates # hole_indices tells earcut where each hole polygon starts in the data array. # In this example, the hole starts at index 4 (since it's a flat array, this is the 5th vertex pair, or 8th element). # No, the example from github passes non-flattened array, and `[4]` refers to the 4th *point* index. # So, data should *not* be flattened prior to passing, it seems the C++ binding does that. data_points = np.array([ [10,0], [0,50], [60,60], [70,10], [30,10], [30,30], [20,20], [20,10] ]) # `data_points` is a (N, 2) array. # `hole_indices` is an array of indices where holes start in `data_points`. # `dimensions` is the number of dimensions per point (e.g., 2 for x,y). result_indices = earcut(data_points, [4], 2) # The result is a flat array of vertex indices forming triangles. # For example, [0, 1, 2, 0, 2, 3, ...] means triangle 0 is (data_points[0], data_points[1], data_points[2]). triangles = result_indices.reshape(-1, 3) print(f"Input points:\n{data_points}") print(f"Resulting triangle indices (flat):\n{result_indices}") print(f"Resulting triangles (reshaped):\n{triangles}")