Unity UI检测碰撞

using UnityEngine;
using System.Collections;
using UnityEngine.EventSystems;

public class Test : MonoBehaviour {

void Update () {

if (Input.GetMouseButtonDown(0))
{
Ray ray = Camera.main.ScreenPointToRay(Input.mousePosition);
RaycastHit hitinfo;
if(Physics.Raycast(ray,out hitinfo))
{
GameObject obt = hitinfo.collider.gameObject;
if(obt.name == "Cube" && EventSystem.current.IsPointerOverGameObject()==false)
{
print("碰到了3D模型");
}
}

if (EventSystem.current.IsPointerOverGameObject())
{
print("射线检测UI成功");
}
else
{
print("没有检测到射线");
}
}

}
}