UVMapping.cs

using UnityEngine;
using System.Collections;

[RequireComponent(typeof (MeshFilter))]
[RequireComponent(typeof (MeshRenderer))]
public class UVMapping : MonoBehaviour {

	void Start () {
		float size = 1f;
		Vector3[] vertices = {
			new Vector3(0, size, 0),
			new Vector3(0, 0, 0),
			new Vector3(size, size, 0),
			new Vector3(size, 0, 0),

			new Vector3(0, 0, size),
			new Vector3(size, 0, size),
			new Vector3(0, size, size),
			new Vector3(size, size, size),

			new Vector3(0, size, 0),
			new Vector3(size, size, 0),

			new Vector3(0, size, 0),
			new Vector3(0, size, size),

			new Vector3(size, size, 0),
			new Vector3(size, size, size),
		};

		int[] triangles = {
			0, 2, 1, // front
			1, 2, 3,
			4, 5, 6, // back
			5, 7, 6,
			6, 7, 8, //top
			7, 9 ,8, 
			1, 3, 4, //bottom
			3, 5, 4,
			1, 11,10,// left
			1, 4, 11,
			3, 12, 5,//right
			5, 12, 13


		};


		Vector2[] uvs = {
			new Vector2(0, 0.66f),
			new Vector2(0.25f, 0.66f),
			new Vector2(0, 0.33f),
			new Vector2(0.25f, 0.33f),

			new Vector2(0.5f, 0.66f),
			new Vector2(0.5f, 0.33f),
			new Vector2(0.75f, 0.66f),
			new Vector2(0.75f, 0.33f),

			new Vector2(1, 0.66f),
			new Vector2(1, 0.33f),

			new Vector2(0.25f, 1),
			new Vector2(0.5f, 1),

			new Vector2(0.25f, 0),
			new Vector2(0.5f, 0),
		};	

		Mesh mesh = GetComponent<MeshFilter> ().mesh;
		mesh.Clear ();
		mesh.vertices = vertices;
		mesh.triangles = triangles;
		mesh.uv = uvs;
		mesh.Optimize ();
		mesh.RecalculateNormals ();
	}
}