用于将一个Cylindrical对象的属性值复制到当前对象中。
copy( other: Cylindrical ): Cylindrical
other: 要复制属性值的Cylindrical对象。返回当前对象，即复制后的Cylindrical对象。
const fromCylindrical = new THREE.Cylindrical(5, Math.PI / 3, 10);
const toCylindrical = new THREE.Cylindrical();
toCylindrical.copy(fromCylindrical);
console.log(toCylindrical.radius); // 输出：5
console.log(toCylindrical.theta); // 输出：1.0471975511965976
console.log(toCylindrical.y); // 输出：10