ModelScreenPos = camera.WorldToScreenPoint(Model.transform.position);

q = Quaternion.FromToRotation(OA, OB);

private Vector2 ModelPos;
  private Vector2 mousePos; //當前鼠標位置
  private Vector2 premousePos;//上一幀鼠標位置
  private Quaternion q; 
  private float RotateAngle;
  private Vector3 localEluer; //模型歐拉角存儲變量
 
  private bool IsSelect = false;
  void Start()
  {
    ModelPos = camera.WorldToScreenPoint(go.transform.position);
    angle = localEluer.x = info.opening;
    go.transform.localEulerAngles = localEluer;
  }
 
  public virtual void Update()
  {
    if (Input.GetMouseButtonDown(0)&&modelCamera.IsTouch())
    {
      IsSelect = true;
      premousePos = mousePos=Input.mousePosition; //每次重新點擊的時候都重置鼠標上一幀點擊坐標
    }
    if (Input.GetMouseButton(0)&& IsSelect)
    {
      mousePos = Input.mousePosition;
      RotateAngle = Vector2.Angle(premousePos - ModelPos, mousePos - ModelPos);
      //Debug.Log("RotateAngle+"+RotateAngle);
      if (RotateAngle == 0)
      {
        premousePos = mousePos;
      }
      else
      {
        q = Quaternion.FromToRotation(premousePos - ModelPos, mousePos - ModelPos);
        float k = q.z > 0 ? 1 : -1;
        localEluer.x += k * RotateAngle;
        //Debug.Log(localEluer.x);
        angle = localEluer.x = Mathf.Clamp(localEluer.x, 0, AllowAngle); //這里是項目需要 限制一下旋轉(zhuǎn)圈數(shù)
        go.transform.localEulerAngles = localEluer;
        premousePos = mousePos;
      }
    }
    if (Input.GetMouseButtonUp(0))
    {
      IsSelect = false;
    }  
  }