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About this tool
Generate zebra stripes and natural biological morphogenesis patterns with an interactive Gray-Scott reaction-diffusion simulator.
The Reaction Diffusion Simulator runs the Gray-Scott model directly in your browser: two virtual chemicals share a grid, A is replenished at the feed rate f, B is removed at rate k+f, and the reaction A + 2B to 3B converts one into the other. Each cell updates as A += Da·∇²A − AB² + f(1−A) and B += Db·∇²B + AB² − (k+f)B, with values clamped to 0–1 and the Laplacian taken from a 3×3 kernel weighted −1 at the centre, 0.2 orthogonally and 0.05 diagonally. The two chemical fields live in Float32Arrays and are written straight into a Canvas 2D ImageData buffer inside a requestAnimationFrame loop — no WebGL, no server call, and nothing leaves your device.
Open Reaction Diffusion Simulator on AltFTool — it loads instantly in your browser.
Choose a pattern preset — Zebra Stripes, Leopard Spots, Coral Growth or Maze — from the dropdown; each loads its own feed, kill and diffusion values along with a matching seed layout.
Press Start to run the solver, then move the Feed, Kill, Diffusion A, Diffusion B and Speed sliders while it runs to steer the pattern.
Click or drag on the canvas to inject chemical B and reshape the result; the Live Pattern Stats row tracks coverage (the share of cells where B exceeds 0.18) and grid resolution, while Reset restores the preset seed and Random Seed reseeds with noise.
Zebra Stripes, Leopard Spots, Coral Growth and Maze each load their own feed/kill pair plus a matching seed layout, so a recognisable pattern appears within seconds of pressing Start.
Feed, kill, both diffusion rates and the steps-per-frame speed are live sliders — the solver picks up new values on the very next frame, so you can watch stripes break apart into spots as you drag.
Clicking or dragging injects chemical B into a 9-cell radius disc, letting you seed a pattern by hand instead of only from the presets.
The solver and the canvas rendering both run on your own device; there is no upload, no account and no network request while the simulation runs.
It is a two-chemical Turing model: chemical A is fed into the grid at rate f, chemical B is removed at rate k+f, and wherever they meet the reaction A + 2B to 3B (the AB² term) converts A into B. Because B diffuses more slowly than A — 0.5 against 1.0 in the default preset — the pair settles into stable stripes, spots or mazes instead of mixing evenly.
Feed 0.0367 and kill 0.0649, with diffusion A at 1 and diffusion B at 0.5 — exactly what the Zebra Stripes preset loads. For comparison, Leopard Spots uses feed 0.055 / kill 0.062, Coral Growth uses 0.0545 / 0.062 with a slower B diffusion of 0.45, and Maze uses 0.029 / 0.057.
Because the feed and kill sliders moved outside the narrow band where the pattern survives: when kill + feed removes B faster than the AB² reaction creates it, B decays toward zero and the canvas goes flat. The sliders cover feed 0.010–0.080 and kill 0.030–0.075 in 0.0005 steps, and living patterns occupy only a thin diagonal strip of that space. Press Reset to return to the preset's values and seed.
Yes. Click or drag anywhere on the canvas and the tool injects chemical B into a disc of radius 9 cells, setting B to 1 and A to 0.2 there; the running simulation then grows new structure outward from your stroke. Input goes through pointer events, so touch and stylus work the same way.
Entirely in your browser. The two chemical fields are Float32Arrays stepped in JavaScript and drawn to a Canvas 2D ImageData buffer, with no upload, no signup and no server round-trip — the page never sends your parameters or the resulting pattern anywhere.
Raise the Speed slider, which sets how many solver steps run per animation frame — 1 to 12, with 5 as the default. Grid size also matters: one simulation cell is drawn as a 4-pixel block, so a smaller browser window means fewer cells and a quicker frame. The Resolution tile under the canvas shows the current grid dimensions.
They set how fast each chemical spreads into neighbouring cells — A ranges 0.6–1.4 and B ranges 0.2–0.8. Turing patterns require B to spread more slowly than A, so keep Diffusion B near half of Diffusion A as the presets do; raising B blurs the pattern's edges, lowering it sharpens and fragments them.
There is no download button in this tool, so take a screenshot of the canvas to keep a pattern. Hit Pause first and the frame freezes, which gives a clean capture; the pattern is drawn in your current theme's primary and background colours, so switching between light and dark changes how it looks.