代码如下：

private Transform player;

public float scrollSpeed = 6.0f;

public float roundSpeed = 4.2f;

public float _vMinLimit = 15f; //y min limit

public float _vMaxLimit = 55f; //y max limit

public float zoomMin = 3f;  //zoom min

public float zoomMax = 8f; //zoom max

float hh;

float vv;

float distance;

// Update is called once per frame

void Update () {

if (!player) {

getPlayer();

}

calPos (aroundView (), scrollView ());

}

float scrollView(){

float wheel = Input.GetAxis ("Mouse ScrollWheel");

float dis = Vector3.Distance (transform.position, player.position);

dis -= wheel * scrollSpeed;

distance = Mathf.Clamp (distance,zoomMin,zoomMax);

return distance;

}

Quaternion aroundView(){

float h = Input.GetAxis ("Mouse X");

float v = Input.GetAxis ("Mouse Y");

Quaternion rt = Quaternion.Euler(transform.eulerAngles);

bool rightMouseDown = Input.GetMouseButton (1);

if (rightMouseDown) {

hh += h * roundSpeed; // horizontal

vv -= v;//vertical

vv = Mathf.Clamp(vv,_vMinLimit,_vMaxLimit);

rt = Quaternion.Euler(vv,hh,0f);

}

return rt;

}

//core code

void calPos(Quaternion angle,float distance){

Vector3 pos = angle*new Vector3 (0f,0f,-distance) + player.position;//core code

transform.position = pos;

transform.rotation = angle;//or use the next method

//        transform.LookAt (player.position);

}

void getPlayer(){

player = GameObject.FindGameObjectWithTag (TagsEnum.Player.ToString ()).transform;

hh = transform.eulerAngles.y;

vv = transform.eulerAngles.x;

distance = zoomMax;

}