p5.Quat.js

import p5 from '../core/main';

/**
 * A class to describe a Quaternion
 * for vector rotations in the p5js webgl renderer.
 * @class p5.Quat
 * @constructor
 * @param {Number} [w] Scalar part of the quaternion
 * @param {Number} [x] x component of imaginary part of quaternion
 * @param {Number} [y] y component of imaginary part of quaternion
 * @param {Number} [z] z component of imaginary part of quaternion
 */
p5.Quat = class {
  constructor(w, x, y, z) {
    this.w = w;
    this.vec = new p5.Vector(x, y, z);
  }

  /**
     * Returns a Quaternion for the
     * axis angle representation of the rotation
     *
     * @method fromAxisAngle
     * @param {Number} [angle] Angle with which the points needs to be rotated
     * @param {Number} [x] x component of the axis vector
     * @param {Number} [y] y component of the axis vector
     * @param {Number} [z] z component of the axis vector
     * @chainable
    */
  static fromAxisAngle(angle, x, y, z) {
    const w = Math.cos(angle/2);
    const vec = new p5.Vector(x, y, z).normalize().mult(Math.sin(angle/2));
    return new p5.Quat(w, vec.x, vec.y, vec.z);
  }

  conjugate() {
    return new p5.Quat(this.w, -this.vec.x, -this.vec.y, -this.vec.z);
  }

  /**
     * Multiplies a quaternion with other quaternion.
     * @method mult
     * @param  {p5.Quat} [quat] quaternion to multiply with the quaternion calling the method.
     * @chainable
     */
  multiply(quat) {
    /* eslint-disable max-len */
    return new p5.Quat(
      this.w * quat.w - this.vec.x * quat.vec.x - this.vec.y * quat.vec.y - this.vec.z - quat.vec.z,
      this.w * quat.vec.x + this.vec.x * quat.w + this.vec.y * quat.vec.z - this.vec.z * quat.vec.y,
      this.w * quat.vec.y - this.vec.x * quat.vec.z + this.vec.y * quat.w + this.vec.z * quat.vec.x,
      this.w * quat.vec.z + this.vec.x * quat.vec.y - this.vec.y * quat.vec.x + this.vec.z * quat.w
    );
    /* eslint-enable max-len */
  }

  /**
     * Rotates the Quaternion by the quaternion passed
     * which contains the axis of roation and angle of rotation
     *
     * @method rotateBy
     * @param {p5.Quat} [axesQuat] axis quaternion which contains
     *  the axis of rotation and angle of rotation
     * @chainable
     */
  rotateBy(axesQuat) {
    return axesQuat.multiply(this).multiply(axesQuat.conjugate()).vec;
  }
};

export default p5.Quat;