unity3d简单的相机跟随及视野旋转缩放

1、实现相机跟随主角运动

　　一种简单的方法是把Camera直接拖到Player下面作为Player的子物体，另一种方法是取得Camera与Player的偏移向量，并据此设置Camera位置，便能实现简单的相机跟随了。

　　这里我们选取第二种方法，首先给Camera添加一个脚本，取名为FollowPlayer，脚本很简单不做说明了　

 public class FollowPlayer : MonoBehaviour {

         private Transform player;
         private Vector3 offsetPosition;

     // Use this for initialization
     void Start () {
         player = GameObject.FindGameObjectWithTag(“Player”).transform;
         offsetPosition = transform.position - player.position;
         transform.LookAt(player.position);
     }

     // Update is called once per frame
     void Update () {
         transform.position = offsetPosition + player.position;

     }

2、视野的缩放

　　鼠标滚轮向前拉近视野，向后视野变远。原理是设置一个变量distance为偏移向量的模，鼠标滚轮滑动改变distance的值，然后根据distance设置Camera的位置

　　其中scrollSpeed为定义的一个float变量用于调整缩放的速度

 private float distance;

 private void ScrollView()
     {
         distance = offsetPosition.magnitude;
         //向前滑动拉近 向后滑动拉远
         distance -= Input.GetAxis("Mouse ScrollWheel") * scrollSpeed;
         distance = Mathf.Clamp(distance, MinDistance, MaxDistance);
         offsetPosition = offsetPosition.normalized * distance;
     }

 //然后在Update里面调用ScrollView方法

3、视野旋转

　　采用transform.RotateAround方法，让Camera根据Player的位置旋转

　　

 private void RotateView()
     {
         //鼠标右键按下可以旋转视野
         if (Input.GetMouseButtonDown())
             isRotating = true;
         if (Input.GetMouseButtonUp())
             isRotating = false;

         if (isRotating)
         {
             Vector3 originalPosition = transform.position;
             Quaternion originalRotation = transform.rotation;
             transform.RotateAround(player.position, player.up, rotateSpeed * Input.GetAxis("Mouse X"));
             transform.RotateAround(player.position, transform.right, -rotateSpeed * Input.GetAxis("Mouse Y"));
             float x = transform.eulerAngles.x;
             //旋转的范围为10度到80度
             if (x <  || x > )
             {
                 transform.position = originalPosition;
                 transform.rotation = originalRotation;
             }

         }

         offsetPosition = transform.position - player.position;
     }