void Start()
    {
        terrain_manager    = terrain_manager_game_object.GetComponent <TerrainManager>();
        visibility_corners = GetCorners();
        CorrectionCorners(visibility_corners);
        Debug.Log("starting visibility");
        adjacency_matrix = GetAdjacencyMatrix(visibility_corners);
        dominatingSet    = GreedyDominatingSet(visibility_corners, adjacency_matrix);

        foreach (Vector3 v in dominatingSet)
        {
            terrain_manager.DrawCircle(v, 5, 2);
        }
    }