Have you ever come across an oddly stretched image on the sidewalk, only to find that it looks remarkably realistic if you stand in exactly the right spot? These sidewalk illusions employ a technique called anamorphosis — a special case of perspective art where artists represent 3D views on 2D surfaces. So how is it done? Fumiko Futamura traces the history and mathematics of perspective.

From TED Ed: The mathematics of sidewalk illusions.

Related reading: The Ambassadors (1533), the anamorphic skull painting by Hans Holbein the Younger.

We’ve got quite a few videos that explore anamorphic illusions, too, including Portrait of Innovation: James Conway Farley, Anamorphic Star Wars Shadow Art by Red Hong Yi, Brusspup’s How to make amazing anamorphic illusions, and OK Go’s The Writing’s on the Wall.

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