How to make a Doom Sprite Look from different angles into the main camera

i am having problem to get this done i dont know how to make a mesh with a texture in 2d to face the player from different angles like in Doom the game, for this moment iahve this code and a mesh filter and a meshrenderer could you please help me?

public class Enemy : Entity
    Transform player;
    public float angle;
    Vector3 direction;

    public MeshRenderer spriteObj;

    public Texture[] mat;
    Texture F = Resources.Load<Texture>("Sprites/F") as Texture;
    Texture FR = Resources.Load<Texture>("Sprites/FR") as Texture;
    Texture R = Resources.Load<Texture>("Sprites/R") as Texture;
    Texture BR = Resources.Load<Texture>("Sprites/BR") as Texture;
    Texture B = Resources.Load<Texture>("Sprites/B") as Texture;
    Texture FL = Resources.Load<Texture>("Sprites/FL") as Texture;
    Texture L = Resources.Load<Texture>("Sprites/L") as Texture;
    Texture BL = Resources.Load<Texture>("Sprites/BL") as Texture;

    // Use this for initialization
    public Enemy() : base("Enemy")
        player = GameObject.FindWithTag("Player").transform;
        mat = new Texture[8] { F, FR, R, BR, B, BL, L, FL};

    // Update is called once per frame
    override public void Update()
        direction = player.transform.position - skin.transform.position;
        angle = Mathf.Atan2(direction.x, direction.z) * Mathf.Rad2Deg;

    void ChangeDirection()
        if (angle < 0) angle += 360; // Just in case
        skin.GetComponent<MeshRenderer>().material.mainTexture = mat[Mathf.FloorToInt(angle / 360f * mat.Length) % mat.Length];

Just use Transform.LookAt(transform target) in Update to look at the target.