// Use this for initialization
 void Start()
 {
     System.Diagnostics.Stopwatch watch = new System.Diagnostics.Stopwatch();
     watch.Start();
     itm = NavMeshBuilder.BuildTerrainNavmesh(GameObject.FindObjectOfType <Terrain>());
     Debug.Log("Terrain built in " + watch.Elapsed);
     watch.Reset(); watch.Start();
     StartCoroutine(itm.OptimizeMesh());
     StartCoroutine(Draw());
 }