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(1))
            isRotating = true;
        if (Input.GetMouseButtonUp(1))
            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 < 10 || x > 80)
            {
                transform.position = originalPosition;
                transform.rotation = originalRotation;
            }
            
        }

        offsetPosition = transform.position - player.position;
    }