Mitosis in the Gray-Scott model : an introduction to writing shader-based chemical simulations

The Gray Scott Model of Reaction Diffusion is an interesting instance of emergence. By simulating a small chemical system that involves only a few components and reactions, complex and mesmerizing patterns appear.

You can interact with the simulation above by clicking on it to drop some green and you can reset it by pressing the previous (⏮️) button.

Although the local rules and the underlying math are quite simple, there is some heavy computations involved. For each time step in the simulation, we must apply these rules to compute the concentrations of every involved component at every possible location. Running such a simulation on a CPU would be extremely slow. GPUs, however, are specifically built to handle large volumes of a single small computation in parallel.

This post is an introduction to writing such simulations using GLSL ES, with a basic implementation of the Gray Scott model that runs in the browser on Shadertoy that is less than 100 lines of code.

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