Substance Material - Simple Wood

When studying the wobbly wood grain, I saw that they sort of resemble the lines on a topographical map. At that point, my mind easily wrapped around the idea of recreating the effect. Make a heightfield, distort it a bit, quantize greyscale it, then edge detect. That's basically it. Then it's a matter of non-uniform blurring it vertically to get the subtle smearing/darkening.