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

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

import { addW4 } from "@thi.ng/vectors/addw";
import { normalize } from "@thi.ng/vectors/normalize";
const cubicTangentAt = (out, a, b, c, d, t, len = 1) => {
  const s = 1 - t;
  const ss = s * s;
  const tt = t * t;
  const ts2 = 2 * t * s;
  return normalize(
    out,
    addW4(out, a, b, c, d, -3 * ss, 3 * (ss - ts2), 3 * (ts2 - tt), 3 * tt),
    len
  );
};
export {
  cubicTangentAt
};