Generate Infinite

using UnityEngine;
using System.Collections;

class Tile
{
	public GameObject theTile;
	public float creationTime;

	public Tile(GameObject t, float ct)
	{
		theTile = t;
		creationTime = ct;
	}
}


public class GenerateInfinite : MonoBehaviour {

	public GameObject plane;
	public GameObject player;

	int planeSize = 10;
	int halfTilesX = 10;
	int halfTilesZ = 10;

	Vector3 startPos;

	Hashtable tiles = new Hashtable();

	void Start ()
	{
		this.gameObject.transform.position = Vector3.zero;
		startPos = Vector3.zero;

		float updateTime = Time.realtimeSinceStartup;

		for (int x = -halfTilesX; x < halfTilesX; x++)
		{
			for (int z = -halfTilesZ; z < halfTilesZ; z++)
			{
				Vector3 pos = new Vector3 ((x * planeSize + startPos.x),
					                                     0,
					                       (z * planeSize + startPos.z));
				GameObject t = (GameObject)Instantiate (plane, pos, Quaternion.identity);

				string tilename = "Tile_" + ((int)(pos.x)).ToString () + "_" + ((int)(pos.z)).ToString ();
				t.name = tilename;
				Tile tile = new Tile (t, updateTime);
				tiles.Add (tilename, tile);
			}
		}
	}


	void Update ()
	{
		//Determine how far the player has moved since last update
		int xMove = (int)(player.transform.position.x - startPos.x);
		int zMove = (int)(player.transform.position.z - startPos.z);

		if (Mathf.Abs (xMove) >= planeSize || Mathf.Abs (zMove) >= planeSize)
		{
			float updateTime = Time.realtimeSinceStartup;

			//Force integer position and round to nearest tilesize
			int playerX = (int)(Mathf.Floor(player.transform.position.x/planeSize) * planeSize);
			int playerZ = (int)(Mathf.Floor(player.transform.position.z/planeSize) * planeSize);

			for (int x = -halfTilesX; x < halfTilesX; x++)
			{
				for (int z = -halfTilesZ; z < halfTilesZ; z++)
				{
					Vector3 pos = new Vector3 ((x * planeSize + playerX),
						                                     0,
						                       (z * planeSize + playerZ));

					string tilename = "Tile_" + ((int)(pos.x)).ToString () + "_" + ((int)(pos.z)).ToString ();

					//If the tile isnt already in the hashtable (created), make a new one
					if (!tiles.ContainsKey (tilename))
					{
						GameObject t = (GameObject)Instantiate (plane, pos, Quaternion.identity);
						t.name = tilename;
						Tile tile = new Tile (t, updateTime);
						tiles.Add (tilename, tile);
					}

					//Tile already exists, update the timestamp
					else
					{
						(tiles [tilename] as Tile).creationTime = updateTime;
					}
				}
			}

			//Destroy all tiles not just created or updated
			//and put new tiles and tiles to be kept in a new hashtable
			Hashtable newTerrain = new Hashtable();
			foreach (Tile tls in tiles.Values)
			{
				if (tls.creationTime != updateTime) {
					//Delete gameobject
					Destroy (tls.theTile);
				}

				else
				{
					newTerrain.Add (tls.theTile.name, tls);
				}
			}

			//Copy new hashtable contents to the working hashtable
			tiles = newTerrain;

			startPos = player.transform.position;
		}
	}
}