Anamorphic Mirror
Anamorphic art uses deliberate distortion so that an image appears correct only when viewed in a curved mirror. Here a cylindrical mirror sits at the center of a circular surface. Draw in the "intended image" view, and the tool computes the radially stretched anamorphic distortion needed so that the cylinder's reflection reconstructs your drawing. The geometric mapping converts each point from polar coordinates around the mirror into the reflected angle off the curved surface.
How Cylindrical Anamorphosis Works
Place a cylindrical mirror at the center of a flat surface. For each point on the surface, a light ray travels to the cylinder, reflects off its curved surface according to the law of reflection, and reaches the viewer's eye. The curvature of the cylinder compresses the reflected image radially — points farther from the cylinder are compressed more. By pre-distorting the artwork in the inverse direction (stretching it radially), the reflection undoes the distortion and the image appears correct.
The Polar Inversion
In polar coordinates centered on the mirror, a point at radius r and angle θ on the intended image maps to r' = R²/r on the anamorphic surface, where R is the mirror radius. Points near the mirror get mapped far away, and distant points get mapped close — this is a circle inversion. The angular coordinate θ is preserved (for an ideal vertical cylinder), so the distortion is purely radial: the image is stretched outward like a rubber sheet pulled from the center.
History
Anamorphic art dates to the Renaissance. Leonardo da Vinci created some of the earliest known examples around 1485. The technique became popular in the 17th and 18th centuries as a form of visual puzzle and hidden imagery. Cylindrical mirror anamorphosis was particularly prized because the undistorted image is invisible until the mirror is placed, creating a dramatic reveal.