u3d：鼠标控制摄像机围绕对象旋转 ，用于观察对象

using UnityEngine;
//观察模型
public class MouseFollowRotation : MonoBehaviour
{

    public Transform target;
    public float xSpeed = 200, ySpeed = 200, mSpeed = 10;
    public float yMinLimit = -50, yMaxLimit = 50;
    public float distance = 9, minDistance = 3, maxDistance = 30;

    //bool needDamping = false;
    public bool needDamping = true;
    float damping = 5.0f;

    public static float x = 0.0f;
    public static float y = 0.0f;


    void Start()
    {
        //    target = GameObject.Find ("Cube").transform;
        Vector3 angles = transform.eulerAngles;
        x = angles.y;
        y = angles.x;
    }

    // Update is called once per frame
    void LateUpdate()
    {


        if (target)
        {
            if (Input.GetMouseButton(1))
            {
                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);
    //}
}