鼠标控制屏幕旋转缩放

    public Transform target;
    public float xSpeed = 200, ySpeed = 200, mSpeed = 10;
    public float yMinLimit = -50, yMaxLimit = 50;
    public float distance = 7, minDistance = 2, maxDistance = 30;
    //bool needDamping = false;
    public bool needDamping = true;
    float damping = 5.0f;
    public float x = 0.0f;
    public float y = 0.0f;

    public void SetTarget(GameObject go) {
        target = go.transform;
    }

    void LateUpdate() {
        //print("LateUpdate()");
        if (target) {
            //use the light button of mouse to rotate the camera
            if (Input.GetMouseButton(0)) {
                x += Input.GetAxis("Mouse X") * xSpeed * 0.02f;
                y -= Input.GetAxis("Mouse Y") * ySpeed * 0.02f;

                y = ClampAngle(y, yMinLimit, yMaxLimit);
            }
            //print("LateUpdate()");
            if (Input.GetMouseButton(2)) {
                print("if (Input.GetMouseButton(2)) {");
                x += Input.GetAxis("Mouse X") * xSpeed * 0.02f;
                y -= Input.GetAxis("Mouse Y") * ySpeed * 0.02f;

                y = ClampAngle(y, yMinLimit, yMaxLimit);
            }

            distance -= Input.GetAxis("Mouse ScrollWheel") * mSpeed;
            distance = Mathf.Clamp(distance, minDistance, maxDistance);

            Quaternion rotation = Quaternion.Euler(y, x, 0.0f);
            Vector3 disVector = new Vector3(0.0f, 0.0f, -distance);
            Vector3 position = rotation * disVector + target.position;
            //adjust the camera

            if (needDamping) {
                transform.rotation = Quaternion.Lerp(transform.rotation, rotation, Time.deltaTime * damping);
                transform.position = Vector3.Lerp(transform.position, position, Time.deltaTime * damping);
            }
            else {
                transform.rotation = rotation;
                transform.position = position;
            }
        }
    }

    static float ClampAngle(float angle, float min, float max) {
        if (angle < -360)
            angle += 360;
        if (angle > 360)
            angle -= 360;
        return Mathf.Clamp(angle, min, max);
    }