unity3d视角跟随鼠标左右上下转动

using UnityEngine;
using System.Collections;
//1.设置Axes为Mouse X  QQ群：476842922(欢迎加群讨论学习)
// MouseLook rotates the transform based on the mouse delta.
// To make an FPS style character:
// - Create a capsule.
// - Add the MouseLook script to the capsule.
//   -> Set the mouse look to use MouseX. (You want to only turn character but not tilt it)
// - Add FPSInput script to the capsule
//   -> A CharacterController component will be automatically added.
//
// - Create a camera. Make the camera a child of the capsule. Position in the head and reset the rotation.
// - Add a MouseLook script to the camera.
//   -> Set the mouse look to use MouseY. (You want the camera to tilt up and down like a head. The character already turns.)

[AddComponentMenu("Control Script/Mouse Look")]
public class MouseLook : MonoBehaviour {
    public enum RotationAxes {
        MouseXAndY = 0,
        MouseX = 1,
        MouseY = 2
    }
    public RotationAxes axes = RotationAxes.MouseXAndY;

    public float sensitivityHor = 9.0f;
    public float sensitivityVert = 9.0f;
    
    public float minimumVert = -45.0f;
    public float maximumVert = 45.0f;

    private float _rotationX = 0;
    
    void Start() {
        // Make the rigid body not change rotation
        Rigidbody body = GetComponent<Rigidbody>();
        if (body != null)
            body.freezeRotation = true;
    }

    void Update() {
        if (axes == RotationAxes.MouseX) {
            transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityHor, 0);
        }
        else if (axes == RotationAxes.MouseY) {
            _rotationX -= Input.GetAxis("Mouse Y") * sensitivityVert;
            _rotationX = Mathf.Clamp(_rotationX, minimumVert, maximumVert);
            
            transform.localEulerAngles = new Vector3(_rotationX, transform.localEulerAngles.y, 0);
        }
        else {
            float rotationY = transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityHor;

            _rotationX -= Input.GetAxis("Mouse Y") * sensitivityVert;
            _rotationX = Mathf.Clamp(_rotationX, minimumVert, maximumVert);

            transform.localEulerAngles = new Vector3(_rotationX, rotationY, 0);
        }
    }
}