deepgrain-foundry/src/render/gpu/surface.js

const SM = { t0: performance.now(), surf: -1 };
function smoothSurface() {
  if (SM.surf < 0 || SM.surfSeed !== worldSeed || SM.surfW !== W) { SM.surf = meanSurface(); SM.surfW = W; SM.surfSeed = worldSeed; }
  return SM.surf;
}