private TileState stateFrom(boolean is_passable, boolean is_opaque) {

        if (is_opaque) {
            if (is_passable) {
                return TileState.PASSABLE_OPAQUE;
            }

            return TileState.IMPASSABLE_OPAQUE;
        } else {
            if (is_passable) {
                return TileState.PASSABLE_TRANSPARENT;
            }
            return TileState.IMPASSABLE_TRANSPARENT;
        }

    }