look.cs

using UnityEngine;
using System.Collections;

public class Looky : MonoBehaviour 
{
	/**
	 * The target for where we want to face
	 */
	public Transform target;
	
	/**
	 * The child socket transforms
	 */
	public Transform[] sockets;

	/**
	 * Indicates which socket we are using.
	 * @type {Number}
	 */
	public int index = 0;

	/**
	 * The speed in which the rotation will occur over time.
	 */
	public float rotationSpeed;
	
	/**
	 * Rotates the cube so that the chosen socket is orientated toward the target 
	 * transform.
	 */
	void Update () 
	{
		// Draw some debug lines to each socket.
		for(int i = 0; i < sockets.Length; i++)
		{
			Debug.DrawLine(transform.position, sockets[i].transform.position, Color.green);
		}

		if (sockets[index] != null) 
		{
			// This is the forward vector
			Vector3 forward = target.transform.position - transform.position;

			// this is the local direction to the socket
			Vector3 dir = sockets[index].transform.localPosition - Vector3.zero;
			Quaternion rot = Quaternion.FromToRotation(Vector3.forward, -dir);

			// look at the forward direction and also rotate with the extra socket rotation
			Quaternion lookRotation = Quaternion.LookRotation(forward) * rot;

			// slerp the transform rotation
			transform.rotation = Quaternion.Slerp(transform.rotation, lookRotation, Time.deltaTime * rotationSpeed);
		}
	}
}