Anamorphic street art only looks correct from extreme angles

Those massive, mind-bending chalk drawings of gaping chasms on the sidewalk are mathematically warped nightmares from any other vantage point. The artists stretch the vertical perspective out to absurd lengths to force a 3D illusion on the retina. If you step five feet to the left of the intended viewing spot, the terrifying canyon just looks like a long, smeared smudge.