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

public class Rata : MonoBehaviour {

public Vector3 mousepos;
// Use this for initialization
void Start () {
	
}

// Update is called once per frame
void Update () {
    

}
private IEnumerator OnMouseDown()
{
    mousepos = Input.mousePosition;
    while(Input.GetMouseButton(0))
    {
        Vector3 offset = mousepos - Input.mousePosition;
        transform.Rotate(Vector3.up * offset.x*Time.deltaTime*20, Space.World);左右滑动 20是旋转的速度
        //transform.Rotate(Vector3.right * offset.y, Space.World);//上下滑动
        mousepos = Input.mousePosition;
        yield return null;
    }
}

}
//把脚本放到需要旋转的物体上

也可以这样

private IEnumerator OnMouseDown()
{
mousepos = Input.mousePosition;
return null;
}
private IEnumerator OnMouseDrag()
{

    Vector3 offset = mousepos - Input.mousePosition;
    transform.Rotate(Vector3.up * offset.x * Time.deltaTime * 20, Space.World);
    //transform.Rotate(Vector3.right * offset.y, Space.World);
    mousepos = Input.mousePosition;
    yield return null;
}