code: function() {
          return {
              theta: Math.atan2(this.z, this.x),
              phi: Math.asin(this.y / this.length())
          };
      }
docs: Computes the theta & phi angles of the vector.
  @memberof Vec3#
  @returns {object} ret
  @returns {Number} ret.theta - angle from the xz plane
  @returns {Number} ret.phi - angle from the y axis