Unity3D显示帧率以及设置不限制帧率

using UnityEngine;
using System.Collections;

public class Fps : MonoBehaviour
{
    float updateInterval = 0.5f;
    private float accum = 0.0f; 
    private float frames = 0; 
    private float timeleft; 
    // Use this for initialization
    void Start()
    {
        if (!guiText)
        {
            enabled = false;
            return;
        }
        timeleft = updateInterval;
    }

    // Update is called once per frame
    void Update()
    {
        timeleft -= Time.deltaTime;
        accum += Time.timeScale / Time.deltaTime;
        ++frames;

        if (timeleft <= 0.0)
        {
            guiText.text = "" + (accum / frames).ToString("f2");
            timeleft = updateInterval;
            accum = 0.0f;
            frames = 0;
        }
    }
}