Dang! I started working mid-last year on practically exactly this as a side project (was going to call the paper "Towards the horse", if you get the reference :) ). Congratulation for making it work, I am really psyched. Can you remember what triggered the motivation to work on this? Somehow I remember there being something on reaction-diffusion equations on HN around that time. Had you tried to use a single Laplace operator instead of two Sobel filters? My approach is to model the reaction-diffusion as a sum of 1x1-convolution (reaction) and a depthwise 3x3 convolution with a fixed kernel multiplied by a learnable constant (diffusion). However, for this to work, a single seed pixel obviously will not work. Any thoughts?