Billboard Unity3D

using UnityEngine;
using System.Collections;

public class BillboardYAxis : MonoBehaviour {

    private Camera camToLookAt;

    //============================================

    void Awake()
    {
        if (Camera.main != null)
            camToLookAt = Camera.main;
    }

    //============================================

    void Update()
    {
        if (Camera.main != null)
        {
            Vector3 v = camToLookAt.transform.position - transform.position;
            v.x = 0.0f;
            v.z = 0.0f;
            transform.LookAt(camToLookAt.transform.position - v);
        }
    }

}