Unity实现鼠标点2D转3D进行旋转

using UnityEngine;

public class GunFollowMouse : MonoBehaviour {
  public RectTransform UGUICanvas;
  public Camera mainCamera;
  //摄像机旋转的缓动速率
  private float rotateSpeed = 5;
  void Start () {
 
 }
 
 void Update () {
    //定义一个世界坐标的鼠标点
    Vector3 mousePos;
    //获取当前canvas下鼠标的二维坐标点 转化为三维 out出来
    RectTransformUtility.ScreenPointToWorldPointInRectangle(UGUICanvas,
      new Vector2(Input.mousePosition.x, Input.mousePosition.y),
      mainCamera, out mousePos
      );
    //炮台的旋转角度
    float angle;
    //向量dirMouse为鼠标的向量减去枪的起始向量得到枪到鼠标位置的方向向量
    Vector3 dirMouse = mousePos - transform.position;
    angle = Vector3.Angle(dirMouse, Vector3.up);//直接得到两个向量之间的夹角,这个角度是没有正负的
    if (mousePos.x > transform.position.x)
    {
      angle = - angle;
    }
    transform.localRotation = Quaternion.Lerp(transform.localRotation, Quaternion.Euler(0, 0, angle)
      , Time.deltaTime * rotateSpeed);
 }
}