I love fun illusions, and I happened upon one that’s pretty interesting to see: an artist draws a glass of water that is startlingly 3-D:
Oddly, the illusion is actually more convincing to watch at lower resolution and with a smaller window; that washes out the pencil strokes and actually makes the illusion more realistic. I can’t remember the last time I saw something like that.
This type of art is becoming common in street drawing; a Web search will yield a bazillion very cool examples.
This technique is called forced perspective, in that it takes the cues your eyes and brain use to estimate relative distance (like, when one object is closer than another) and plays with them, forcing you to interpret those cues a certain way.
When the artist rotates the drawing so the top of the glass is toward you, it looks all weird and distorted because your brain is confused. I love the irony; it shows you this is a drawing and not real, yet your brain may take a moment or two to actually settle with that. Our brains just love to be fooled.
... and please check out what I still consider the single greatest illusion of all time.
Tip o’ the Necker Cube to David Darling.
*He claims I’m the evil one, thus proving he’s the evil one.