Unity3d中角色模型和角色名字保持相对位置

/*
date:2014-10-13
author:wg
description:英雄名字面板
*/

using UnityEngine;
using System.Collections;

public class NamePanel : MonoBehaviour
{
    [SerializeField]
    UILabel lblName;

    [SerializeField]
    GameObject obj;

    [SerializeField]
    Camera mainCamera;

    [SerializeField]
    Camera uiCamera;

    void Update()
    {
        UpdateNamePosition();
    }

    Vector3 m_position;
    /// <summary>
    /// 更新名字位置
    /// </summary>
    void UpdateNamePosition()
    {
        //取模型在主摄像机中的世界坐标
        m_position = obj.transform.position;
        //转换为主摄像机的屏幕坐标
        m_position = mainCamera.WorldToScreenPoint(m_position);
        //用得到的屏幕坐标，在UI摄像机中转换为世界坐标
        m_position = uiCamera.ScreenToWorldPoint(m_position);
        m_position.z = 0f;
        m_position.y += 0.1f;
        lblName.transform.position = m_position;
    }
}