Unity3d billboard 公告板技术

using UnityEngine;
using System.Collections;

public class LookAtCameraYRotationOnly : MonoBehaviour
{
public Camera cameraToLookAt;

void Update() 
    {
        Vector3 v = cameraToLookAt.transform.position - transform.position;
        v.x = v.z = 0.0f;
        transform.LookAt(cameraToLookAt.transform.position - v); 
    }
}