unity3d簡單的相機跟隨及視野旋轉縮放

1、實現相機跟隨主角運動

　　一種簡單的方法是把Camera直接拖到Player下面作為Player的子物體，另一種方法是取得Camera與Player的偏移向量，並據此設置Camera位置，便能實現簡單的相機跟隨了。

　　這里我們選取第二種方法，首先給Camera添加一個腳本，取名為FollowPlayer，腳本很簡單不做說明了　

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、視野的縮放

　　鼠標滾輪向前拉近視野，向后視野變遠。原理是設置一個變量distance為偏移向量的模，鼠標滾輪滑動改變distance的值，然后根據distance設置Camera的位置

　　其中scrollSpeed為定義的一個float變量用於調整縮放的速度

private float distance;

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

//然后在Update里面調用ScrollView方法

3、視野旋轉

　　采用transform.RotateAround方法，讓Camera根據Player的位置旋轉

　　

private void RotateView()
    {
        //鼠標右鍵按下可以旋轉視野
        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;
            //旋轉的范圍為10度到80度
            if (x < 10 || x > 80)
            {
                transform.position = originalPosition;
                transform.rotation = originalRotation;
            }
            
        }

        offsetPosition = transform.position - player.position;
    }