"Eroded" fBm (Iñigo Quilez): each octave is damped by the slope accumulated so far, giving smooth valley floors and sharp gullies without simulating erosion. Returns roughly [-1, 1].
0 = plain fBm, larger = stronger slope damping.
"Eroded" fBm (Iñigo Quilez): each octave is damped by the slope accumulated so far, giving smooth valley floors and sharp gullies without simulating erosion. Returns roughly [-1, 1].