Unity 第一人称 使照相机跟随主角移动

using UnityEngine;
using System.Collections;
//应把物机添加Character Controller组件.
public class Cubet : MonoBehaviour {     //此处定义一个类，所拖动到的物体即是该类的一个对象

	public enum RotationAxes { MouseXAndY = 0, MouseX = 1, MouseY = 2 }
	public RotationAxes axes = RotationAxes.MouseXAndY;
	public float sensitivityX = 15F;
	public float sensitivityY = 15F;
	
	public float minimumX = -360F;
	public float maximumX = 360F;
	
	public float minimumY = -60F;
	public float maximumY = 60F;
	
	float rotationY = 0F;

	public Transform cam_transform;
	public Transform per_transform;
	// Use this for initialization
	void Start () {
		per_transform = this.transform;   //获取对象的transform，包括有旋转角度，位置等。此处已相当于指针指向了
		GameObject cobj = GameObject.Find ("mainCamera");   //获取照相机
		cam_transform = cobj.transform;	//照相机的transform
		camStart ();
		if (GetComponent<Rigidbody>())	//旋转冻结。作用是用于使旋转角度不因物理模拟而改变。
			GetComponent<Rigidbody>().freezeRotation = true;
	}

	void camStart(){
		Vector3 perpos = per_transform.position;
		perpos.y += 0.5f;
		perpos.x += 1f;
		perpos.z += 1f;
		cam_transform.position = perpos;	//设置照相机的位置、角度
		cam_transform.eulerAngles = per_transform.eulerAngles;
	}

	// Update is called once per frame
	void Update () {	//官方的代码
		if (axes == RotationAxes.MouseXAndY)
		{
			float rotationX = cam_transform.localEulerAngles.y + Input.GetAxis("Mouse X") * sensitivityX;
			
			rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
			rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
			
			cam_transform.localEulerAngles = new Vector3(-rotationY, rotationX, 0);
		}
		else if (axes == RotationAxes.MouseX)
		{
			cam_transform.Rotate(0, Input.GetAxis("Mouse X") * sensitivityX, 0);
		}
		else
		{
			rotationY += Input.GetAxis("Mouse Y") * sensitivityY;
			rotationY = Mathf.Clamp (rotationY, minimumY, maximumY);
			
			cam_transform.localEulerAngles = new Vector3(-rotationY, transform.localEulerAngles.y, 0);
		}
		per_transform.localEulerAngles = cam_transform.transform.localEulerAngles;	//设置对象的面向始终与照相机的面向保持一致。
	}
}