Ear clipping

Ear = vertex whose triangle with neighbors is inside polygon + contains no other vertices. Repeatedly clip ears.

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Complexity

Ear clipping: O(N²) with straightforward implementation. Sweep-line: O(N log N). Chazelle 1991: O(N) — impractical constants.

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Convex polygon

Trivial: fan from any vertex. O(N). All triangulations of convex polygon have same triangle count = N - 2.

Applications

3D graphics (send triangles to GPU). Physics simulation. FEM meshing.