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Fourier Epicycles Drawing Machine — Draw a Path, See the DFT Redraw It

Draw any closed path with your mouse and watch a chain of rotating vectors — epicycles, sized and timed by a Discrete Fourier Transform of your drawing — trace it back out in real time. It is a direct visual demonstration of the same idea Joseph Fourier proved centuries ago: any periodic curve, no matter how complex, can be built from a sum of simple rotating circles.

How to use Fourier Epicycles Drawing Machine

  1. Draw a closed path with your mouse.
  2. Watch the DFT compute the epicycle vectors from your drawing.
  3. See the chain of rotating circles retrace your path.
  4. Adjust how many epicycles are used and watch the fidelity change.

Frequently asked questions

What is an epicycle in this context?
A vector rotating at a constant speed around the tip of another rotating vector — chaining many of them together, each sized and timed by the Fourier transform of your drawing, reconstructs the original path.
Is this the actual Fourier transform, or a visual approximation?
It is a real Discrete Fourier Transform of the path you draw, decomposed into frequency components that are then visualised as the rotating epicycle vectors — not a simplified stand-in animation.
Why does using fewer epicycles make the drawing less accurate?
Each epicycle corresponds to one frequency component; dropping the higher-frequency (finer-detail) components for speed leaves only the broad shape, the same trade-off any Fourier-based compression makes.

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