ret->push_front (b.sloped_neighbour (horizon_padding, LEFT));
if (!isinf (b.iv_[LEFT]))
ret->push_front (Building (-infinity_f, -infinity_f,
ret->push_front (b.sloped_neighbour (horizon_padding, LEFT));
if (!isinf (b.iv_[LEFT]))
ret->push_front (Building (-infinity_f, -infinity_f,