normal.glsl

float sSphere(vec3 p, float time) {
  return length(p) - 1.0 - noise(p, time) * 0.05;
}

vec3 calcNormal(vec3 p, float time) {
  const float eps = 0.002;
  const vec2 offset = vec2(1.0, -1.0);

  return normalize(
    offset.xyy * sSphere(p + offset.xyy * eps, time) +
    offset.yyx * sSphere(p + offset.yyx * eps, time) +
    offset.yxy * sSphere(p + offset.yxy * eps, time) +
    offset.xxx * sSphere(p + offset.xxx * eps, time)
  );
}