@thi.ng/matrices/quat-axis-angle.js

Matrix & quaternion operations for 2D/3D geometry processing

import { EPS } from "@thi.ng/math/api";
import { normalize3, normalize4 } from "@thi.ng/vectors/normalize";
const quatFromAxisAngle = (axis, theta) => {
  theta *= 0.5;
  return normalize3([0, 0, 0, Math.cos(theta)], axis, Math.sin(theta));
};
const quatToAxisAngle = (quat) => {
  const n = normalize4([], quat);
  const w = n[3];
  const m = Math.sqrt(1 - w * w);
  const theta = 2 * Math.acos(w);
  return m > EPS ? [[n[0] / m, n[1] / m, n[2] / m], theta] : [[n[0], n[1], n[2]], theta];
};
export {
  quatFromAxisAngle,
  quatToAxisAngle
};