Generator

The Hopf fibration, drawn with a pen

In 1931 Heinz Hopf described a way to map the 3-sphere, the sphere that lives in four-dimensional space, onto an ordinary sphere. Each point on the ordinary sphere corresponds to a whole circle, called a fibre, and any two fibres are linked exactly once. Project the fibres onto a page and the ones from a single latitude wrap into a torus.

The Hopf Fibration generator draws each fibre as one closed pen stroke. Set Fibres from 8 to 120 and Latitudes from 1 to 5, then turn the shape with Theta, Yaw and Pitch. The back half can stay solid, turn dashed or disappear. Colour By ring gives each latitude its own pen, so a three-latitude piece plots as three nested tori.

The recipe

Enter these settings and the same drawing comes back, line for line.

Generator
Hopf Fibration
Seed
1
Page
AxiDraw V3 · A4, portrait
Pens
Nine Inks
Fibres
80
Latitudes
3
Theta
88
Yaw
150
Pitch
60
Samples
200
Back half
Solid
Colour By
Ring
Three nested tori of linked circles in orange, red and black, drawn by the Forgeplot Hopf Fibration generator.
App preview: this recipe, 240 strokes in three pens.
Reel: “A shape from four dimensions, drawn with a pen.” Our reels feature AI-generated presenters; the app footage and the drawings are real.

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