unity鼠标拖动物体旋转

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

/// <summary>
/// 鼠标控制自旋
/// </summary>
public class SpinWithMouse : MonoBehaviour {

    private bool isClick = false;
    private Vector3 nowPos;
    private Vector3 oldPos;
    float length = ;

    void Start()
    {
        AddBoxCollider();
    }

    void OnMouseUp() { //鼠标抬起
        isClick = false;
    }

    void OnMouseDown() { //鼠标按下

        isClick = true;
    }

    void Update() {
        nowPos = Input.mousePosition;
        if (isClick) { //鼠标按下不松手
            Vector3 offset = nowPos - oldPos;
            if (Mathf.Abs(offset.x) > Mathf.Abs(offset.y) && Mathf.Abs(offset.x) > length) { //进行旋转
                transform.Rotate(Vector3.up,-offset.x);
            }
        }
        oldPos = Input.mousePosition;
    }

    /// <summary>
    /// 添加Collider作为鼠标检测区域
    /// </summary>
    public void AddBoxCollider()
    {
        BoxCollider box = gameObject.AddComponent<BoxCollider>();
        //参数
        box.center = new Vector3(, 1.2f, );
        box.size = new Vector3(2.4f, 2.4f, 2.4f);
    }
}

本来想用射线检测，发现unity生命周期自己带这个，挺方便的，脚本直接挂在物体上就行