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Hardware Heritage
Lissajous figures are the graphs of a system of parametric equations which describe complex harmonic motion. They were the "screensavers" of the analog age.
Oscilloscopes
Feeding sine waves into the X and Y inputs of an oscilloscope creates these patterns. Sci-fi movies used them to look "high-tech."
Vector Monitors
Arcade machines like *Asteroids* or the Vectrex console used vector beams instead of raster lines, capable of drawing infinitely smooth curves.
Phosphor
The glowing trail (persistence) is caused by the phosphor on the CRT screen not fading instantly. We simulate this with alpha blending.
Lissajous
Harmonic parametric curves.
The Math
x = A * sin(a*t + delta) y = B * sin(b*t)