@thi.ng/geom-tessellate/tri-fan-split.js

2D/3D convex polygon tessellators

import { centroid } from "@thi.ng/geom-poly-utils/centroid";
import { addmN } from "@thi.ng/vectors/addmn";
const triFanSplit = (tess, faces, pids) => {
  const points = tess.pointsForIDs(pids);
  const c = centroid(points);
  const cid = tess.addPoint(c);
  const n = pids.length - 1;
  for (let i = 0; i <= n; i++) {
    const j = i < n ? i + 1 : 0;
    const a = points[i];
    const b = points[j];
    const mab = tess.addPoint(addmN([], a, b, 0.5));
    const mac = tess.addPoint(addmN([], a, c, 0.5));
    const mbc = tess.addPoint(addmN([], b, c, 0.5));
    faces.push(
      [pids[i], mab, mac],
      [mab, pids[j], mbc],
      [mac, mab, mbc],
      [mac, mbc, cid]
    );
  }
  return faces;
};
export {
  triFanSplit
};