curl noise for ThreeJS; this gist is open source under MIT license.

curl.js

const SimplexNoise = require('simplex-noise');
const simplex = new SimplexNoise();

module.exports = curlNoise;
function curlNoise (x, y, z, out = new THREE.Vector3()) {
  const eps = 1.0;
  let n1, n2, a, b;

  n1 = simplex.noise3D(x, y + eps, z);
  n2 = simplex.noise3D(x, y - eps, z);

  a = (n1 - n2) / (2 * eps);

  n1 = simplex.noise3D(x, y, z + eps);
  n2 = simplex.noise3D(x, y, z - eps);

  b = (n1 - n2) / (2 * eps);

  out.x = a - b;

  n1 = simplex.noise3D(x, y, z + eps);
  n2 = simplex.noise3D(x, y, z - eps);

  a = (n1 - n2)/(2 * eps);

  n1 = simplex.noise3D(x + eps, y, z);
  n2 = simplex.noise3D(x + eps, y, z);

  b = (n1 - n2)/(2 * eps);

  out.y = a - b;

  n1 = simplex.noise3D(x + eps, y, z);
  n2 = simplex.noise3D(x - eps, y, z);

  a = (n1 - n2)/(2 * eps);

  n1 = simplex.noise3D(x, y + eps, z);
  n2 = simplex.noise3D(x, y - eps, z);

  b = (n1 - n2)/(2 * eps);

  out.z = a - b;

  return out;
};