2D fractal
Multi-arm
Live turntable captured from Spiralyst Lab.
The multi-arm spiral arranges several identical logarithmic spirals around a shared center, evenly rotated, to form a pinwheel or galaxy-arm motif. The number of arms alone sets its symmetry, from a sweeping two-armed swirl to a luminous many-armed disc.
Pinwheels and Galaxy Arms
Take a single logarithmic spiral and stamp several rotated copies of it around a shared center, evenly spaced, and you get the multi-arm spiral: the pinwheel, the catherine wheel, the classic 'grand-design' galaxy. It is the simplest way to turn one elegant curve into a balanced, radially symmetric composition.
The number of arms sets the entire personality of the figure. Two arms read as a sweeping yin-yang; four or six make a crisp pinwheel; many arms dissolve into a luminous, rotating disc. Because every arm is the same logarithmic spiral — same growth rate, same chirality — just rotated, the figure has exact rotational symmetry, which the eye reads instantly as 'designed'.
Real spiral galaxies are not actually fixed arms but density waves — traffic jams of stars — yet the multi-arm logarithmic model is the eyeball-accurate cartoon astronomers reach for first, because the dominant visual gesture of a galaxy genuinely is a small number of logarithmic arms.
N logarithmic spirals, each offset in starting angle by an equal slice 2π/N — evenly spaced arms sharing one center and one growth rate b.
The single most expressive parameter: it sets the rotational symmetry of the whole figure.
In Spiralyst Lab
Spiralyst Lab draws all N arms (each the log spiral r = a·e^(bθ)), gives each arm its own hue phase, and spins the whole assembly. Map the arm count or rotation to audio and the pinwheel breathes — opening, closing and accelerating with the music. All arms share growth and chirality, so the symmetry stays rigid and clean.
Every parameter below is a live control — set it by hand, map it to a frequency band, or let it ride a smooth animation. These ranges are the actual in-app slider limits.
| Parameter | Range (in-app) |
|---|---|
| Arms | 2 – 12 |
| Turns | 1 – 8 |
| Growth | 0.05 – 0.35 |
Audio-reactive by default: arms 2→8, turns 1→8. Any control can be mapped to audio or animation.
Plus the universal 2D controls every spiral type shares: density & stroke, rotation, squash, jitter, zoom & pan, glow, trails, vignette, and multi-layer stacking (count, hue offset, opacity).
Watch it in action
assets/video/fractals/07-multi-arm.mp4
Did you know: The Milky Way is a barred spiral with two main arms — run this type with N = 2 and a gentle growth rate and you have a passable portrait of our own galaxy.