@thi.ng/geom-tessellate/earcut.js

2D/3D convex polygon tessellators

import { pointInTriangle2 } from "@thi.ng/geom-isec/point";
import { polyArea2 } from "@thi.ng/geom-poly-utils/area";
import { range } from "@thi.ng/transducers/range";
import { signedArea2 } from "@thi.ng/vectors/signed-area";
const earCut = (tess, faces, pids) => {
  let n = pids.length;
  const points = tess.pointsForIDs(pids);
  const order = [
    ...polyArea2(points) > 0 ? range(n) : range(n - 1, -1, -1)
  ];
  let count = 2 * n - 1;
  let v = n - 1, u, w;
  while (count > 0 && n > 2) {
    u = n <= v ? 0 : v;
    v = u + 1;
    v = n <= v ? 0 : v;
    w = v + 1;
    w = n <= w ? 0 : w;
    if (__snip(points, u, v, w, n, order)) {
      faces.push([pids[order[u]], pids[order[v]], pids[order[w]]]);
      order.splice(v, 1);
      n--;
      count = 2 * n;
    } else {
      count--;
    }
  }
  return faces;
};
const __snip = (points, u, v, w, n, ids) => {
  const a = points[ids[u]];
  const b = points[ids[v]];
  const c = points[ids[w]];
  if (signedArea2(a, b, c) > 0) {
    for (let i = 0; i < n; i++) {
      if (i !== u && i !== v && i !== w) {
        if (pointInTriangle2(points[ids[i]], a, b, c)) {
          return false;
        }
      }
    }
    return true;
  }
  return false;
};
export {
  earCut
};