Simulating epidemics in WebGPU

A few days ago, I simulated an epidemic with WebGL, using a texture for the state of a cellular automaton. However, I got some pretty weird effects. For example, the number of infected people never dropped to zero, despite the math clearly demanding that it should drop to zero.

I concluded that these weird effects were due to my sin of a texture to keep the state of the cells. The texture2d function lets you sample the color of a texture at a specific coordinate. Not a pixel; a coordinate. It does some clever stuff, like mipmapping, “level of detail”, and interpolation. For a cellular automaton, I need a lower-level API, to just access the value at a specific pixel in the texture.

As an extreme solution, I’ve rewritten the epidemic simulation in WebGPU. Earlier, I implemented Game of Life in WebGPU, and I modified that for my epidemic simulation. The API is much more pleasant: instead of the voodoo texture2d function to access pixels of a texture, I can instead directly index into an array of cells.

Gladly, the weird effects are not present in the WebGPU implementation!

Below you should see the simulation – but probably only if you’re running Google Chrome Canary, and you’ve enabled the “Unsafe WebGPU” experiment.

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Tagged #programming, #webgpu, #epidemiology. All content copyright James Fisher 2020. This post is not associated with my employer. Found an error? Edit this page.