@thi.ng/geom-splines/cubic-split.js

nD cubic & quadratic curve analysis, conversion, interpolation, splitting

import { minError } from "@thi.ng/math/min-error";
import { distSq } from "@thi.ng/vectors/distsq";
import { mixCubic } from "@thi.ng/vectors/mix-cubic";
import { mixN } from "@thi.ng/vectors/mixn";
import { set } from "@thi.ng/vectors/set";
const cubicSplitAt = (a, b, c, d, t) => {
  if (t <= 0 || t >= 1) {
    const p2 = t <= 0 ? a : d;
    const c1 = [set([], p2), set([], p2), set([], p2), set([], p2)];
    const c2 = [set([], a), set([], b), set([], c), set([], d)];
    return t <= 0 ? [c1, c2] : [c2, c1];
  }
  const ab = mixN([], a, b, t);
  const bc = mixN([], b, c, t);
  const cd = mixN([], c, d, t);
  const abc = mixN([], ab, bc, t);
  const bcd = mixN([], bc, cd, t);
  const p = mixN([], abc, bcd, t);
  return [
    [set([], a), ab, abc, set([], p)],
    [p, bcd, cd, set([], d)]
  ];
};
const splitCubicNearPoint = (p, a, b, c, d, res, iter) => cubicSplitAt(
  a,
  b,
  c,
  d,
  minError(
    (t) => mixCubic([], a, b, c, d, t),
    distSq,
    p,
    res,
    iter
  )
);
export {
  cubicSplitAt,
  splitCubicNearPoint
};