Anamorphosis you walk past every day
Anamorphosis sounds like a gallery word. Most of the examples you actually encounter are municipal, commercial and completely unremarked, and once you notice the first one the rest arrive quickly.
Road markings
Look at a bicycle symbol painted on a road, from directly above if you can, on a bridge or from an upstairs window. It is grotesque: enormously long, the wheels drawn as stretched ellipses, the rider absurdly elongated.
From a driver's seat it looks like a bicycle. A driver sees the road surface at a very shallow angle, so anything on it is compressed front to back, and the marking is drawn pre-stretched by exactly that amount. The same is true of the word BUS, of turn arrows, and of speed numerals, which is why they always look strangely tall and thin from above. This is oblique anamorphosis, applied by a highways department.
Sponsor logos on a pitch
During televised football and rugby you will see brand names that appear to be standing upright on the grass, apparently three dimensional, sometimes seeming to hover. Look at the same pitch from the stands and there is nothing there but a peculiar smear of paint or a stretched decal.
The logo is drawn for the main broadcast camera, in a fixed position, at a known height. Everyone in the stadium sees a distortion. The millions watching at home see the picture. The audience the artwork was made for is the one that is not present.
Painted ceilings
The grandest examples are three hundred years old. Andrea Pozzo painted the ceiling of Sant'Ignazio in Rome in the 1690s with a dome that does not exist and columns that continue the real architecture upwards into an open sky. There is a marble disc set into the floor marking where to stand. From the disc it is seamless. Walk twenty paces and the dome buckles and the columns lean, which is oddly more impressive than the illusion itself.
Emmanuel Maignan's 1642 corridor at Trinita dei Monti does the same in the other direction: it reads as a landscape while you walk along it, and only from the far end does it become a portrait of Saint Francis of Paola.
Signage and safety markings
Airports and stations paint floor markings stretched along the direction of travel, so they read correctly to someone walking towards them rather than standing on them. Some pedestrian crossings in cities have been painted as apparent floating blocks, which is the pavement art trick applied as traffic calming, on the theory that a driver slows for something that looks solid.
Camera angles in film
Forced perspective is the same family. In The Lord of the Rings the hobbits were often not shrunk at all: an actor placed further from the camera along a carefully arranged set reads as smaller, and the shot only works from that one lens position. Any behind the scenes photograph of such a set looks wrong, because it is taken from the wrong place, and every place except one is the wrong place.
Why the everyday examples are the interesting ones
The gallery examples are made to be admired. The road markings are made to be obeyed, and nobody involved thinks of them as illusions. They are simply the correct way to draw something that will be seen from one predictable position.
That is the useful lesson. Anamorphosis is not a special effect bolted onto normal drawing. Normal drawing is the special case, the one where you have decided the viewer could be anywhere. Choose the viewpoint and the distortion follows automatically.
Our daily puzzle runs it backwards: the picture is already built for a viewpoint, and your job is to work out which one. If you want the construction, it is in why the puzzle always has exactly one answer.