void OnDestroy()
 {
     if (SourceIndex != -1)
     {
         Terrains.RemoveAt(SourceIndex);
         UnusedIndexes.Add(SourceIndex);
         Terrains.Insert(SourceIndex, GameTools.CreateEmptySource());
         NavMeshRegion.StartManualUpdate = true;
         //Debug.Log("Destroyed: " + SourceIndex);
     }
 }
        void OnEnable()
        {
            TheMeshFilter = GetComponent <MeshFilter>();
            TheTerrain    = GetComponent <Terrain>();
            TheCollider   = GetComponent <Collider>();

            if (!HasGeneratedDummySource)
            {
                Terrains.Add(GameTools.CreateEmptySource());
                HasGeneratedDummySource = true;
            }

            Collect();
        }