The smooth function use in the vegetation map to accentuate the values around 0.5 is (x^3 + x + 2)/4. The basic x^3 graph provides the rough curve we want, with a stationary point that we can position around 0.5. We then add the x as we do not what the curve to be 100% stationary, as that would be too extreme. Dividing by 4 reduces the range to [0, 1] with a domain of [-1, 1].