Superellipse

One exponent carries a shape from diamond through circle to near-square. Sweep it across a grid, or nest the whole range inside a single frame.

Superellipse: One exponent carries a shape from diamond through circle to near-square. Sweep it across a grid, or nest the whole range inside a single frame.Superellipse: One exponent carries a shape from diamond through circle to near-square. Sweep it across a grid, or nest the whole range inside a single frame.

About this shape

Gabriel Lamé, 1818 · Piet Hein, 1959

Superellipse, drawn by GART: One exponent carries a shape from diamond through circle to near-square. Sweep it across a grid, or nest the whole range inside a single frame.
Superellipse · CC BY 4.0

The curve is |x/a|ⁿ + |y/b|ⁿ = 1. At n = 1 it is a diamond, at n = 2 an ellipse, and beyond n = 4 it approaches a rounded rectangle, the squircle used for app icons and Piet Hein's Sergels torg. Exponents are interpolated in log space so each step reads as an equal change. Aspect stretches a and b apart.

Behind the mathematics

Piet Hein1905–1996

Superellipse in design

Danish polymath who popularised the superellipse in design and architecture, showing how mathematics can soften the meeting of circle and rectangle.