The 18th century buildings along the Loire river in the Île Feydeau neighborhood of Nantes, France, have tilted rather alarmingly because their foundations were laid on sandy ground.
They dramatically illustrate a point that you can observe more subtly in almost any group of buildings or structures: Things settle a bit and get out of alignment over time. Or they weren’t built perfectly in the first place, especially before the laser-beam era.
When it comes to drawing a row of buildings, it is usually preferable to give them a little wobble. To do that, you can construct a whole set of slightly varying vanishing points.
When it's done very subtly, it gives architectural forms a certain naturalness and believability that beats the kind of cold rendering that comes from aligning an entire parallel facade with a single vanishing point.
(And yes! We saw the machines...more on that in a future post.)