public class HUDPopup : MonoBehaviour 
{
    //目標(biāo)位置  
    private Vector3 mTarget;  
    //屏幕坐標(biāo)  
    private Vector3 mScreen;  
    //傷害數(shù)值  
    public int Value;
    //文本寬度  
    public float ContentWidth;  
    //文本高度  
    public float ContentHeight;
    //GUI坐標(biāo)  
    private Vector2 mPoint;
    //銷毀時(shí)間  
    public float FreeTime = 1.5F;
    public Font font;
    public Color color;
    public int fontSize;
    public float speed;
    void Start ()
    {
        //獲取目標(biāo)位置  
        mTarget = transform.position;  
        //獲取屏幕坐標(biāo)  
        mScreen = Camera.main.WorldToScreenPoint(mTarget);  
        //將屏幕坐標(biāo)轉(zhuǎn)化為GUI坐標(biāo)  
        mPoint = new Vector2(mScreen.x, Screen.height - mScreen.y);  
        //開啟自動(dòng)銷毀線程  
        StartCoroutine("Free");  
    }  
  
    void Update()  
    {  
        //使文本在垂直方向山產(chǎn)生一個(gè)偏移  
        transform.Translate(Vector3.up * speed * Time.deltaTime);
        //重新計(jì)算坐標(biāo)  
        mTarget = transform.position;  
        //獲取屏幕坐標(biāo)  
        mScreen = Camera.main.WorldToScreenPoint(mTarget); 
        //將屏幕坐標(biāo)轉(zhuǎn)化為GUI坐標(biāo)  
        mPoint = new Vector2(mScreen.x, Screen.height - mScreen.y);
    }  
  
    void OnGUI()  
    {  
        //保證目標(biāo)在攝像機(jī)前方  
        if(mScreen.z>0)  
        {  
           //內(nèi)部使用GUI坐標(biāo)進(jìn)行繪制  
           GUIStyle style = new GUIStyle();
           style.fontSize = fontSize;
           style.font = font;
           style.normal.textColor = color;
           GUI.Label(new Rect(mPoint.x, mPoint.y, ContentWidth, ContentHeight), "-"+Value.ToString(),style);
        }  
    }  
  
    IEnumerator Free()  
    {  
        yield return new WaitForSeconds(FreeTime);  
        Destroy(this.gameObject);  
    }  
}  

public class Test : MonoBehaviour
{
    public GameObject popupDamage;
    public Transform hudPos;
    
    private void Update()
    {
        if (Input.GetMouseButtonDown(0))
        {
            GameObject mObject = (GameObject)Instantiate(popupDamage, hudPos.position, Quaternion.identity);
            mObject.GetComponent<HUDPopup>().Value = Random.Range(20, 40);
        }
    }
}