Движение камеры вокруг точки

    private Vector3 point;
    private Camera _camera;
    private GameObject _nullObject;
    private bool _isRMB = false;
 
    void Start () {
        _camera = GetComponent<Camera>();
        
        _nullObject = transform.parent.gameObject;
        //point = GameObject.Find ("Point").transform.position;
    }
    
    void Update () {
        
        if (!Input.GetMouseButton (1) && _isRMB) _isRMB = false;
 
        if (Input.GetMouseButton (1)) {
            if (!_isRMB) {
              _isRMB = true;
              Ray ray = _camera.ScreenPointToRay (Input.mousePosition);
              RaycastHit hit;
              if (Physics.Raycast (ray, out hit))
                 point = hit.point;
            } else {
            _nullObject.transform.RotateAround (point, Vector3.down, Input.GetAxis ("Mouse X"));
            _nullObject.transform.RotateAround (point, _nullObject.transform.right, -Input.GetAxis ("Mouse Y"));
 
            Ray ray = new Ray (point, _nullObject.transform.position - point);
 
            RaycastHit hit;
            if (Physics.Raycast (ray, out hit) && Vector3.Distance(point,hit.point)<Vector3.Distance(point,_nullObject.transform.position)) {
                transform.position = hit.point;
            } else
                transform.position = _nullObject.transform.position;
         }
      }
    }