Layers

Relief and features added to the base, applied in order.

Type	What it is
noise	A stack of fractal noise layers added to the terrain, for hills, ridges and rolling relief.
craters	Impact craters generated from a density and age model, or placed by hand, and cut into the terrain.
boulders	Boulders scattered over the ground from a size distribution, in patches and around fresh craters, as relief or 3D models.
roughness	Fine roughness from octaves of noise, scaled to a given RMS slope over a baseline.
bedforms	Fields of wind-blown ripples or dunes added to the terrain.
scale	Scales and shifts the heights so far, for vertical exaggeration or a datum shift.
clamp	Clamps the heights so far between optional bounds, to flatten a basin floor or cap peaks.
region	Another layer applied only inside a rectangle or circle, feathered outside it: to confine craters to an area or flatten a landing pad.
secondaries	Secondary craters around the craters of the last crater layer before this one, after Singer et al.
dem_detail	Adds the detail a GeoTIFF DEM has above its own low-pass, to restore measured relief over a raster source read with the same low_pass.
dunes	Wind-blown dunes added to the terrain: isolated barchans or domes, or fields of transverse, barchanoid or linear crests, with slip faces and optional ripples on them.
sand_fill	Sand pooled in the lows of the ground beneath: cracks, troughs and hollows between rises, laying sand over the material map.
pavement	Fractured bedrock: polygonal plates, each tilted and stepped, parted by cracks or raised ridges, split again by finer octaves of cracks; lays bedrock over the material map.
strata	Layered rock: the ground beneath terraced into dipping beds, each a flat bench below a cliff, so hills become stepped buttes and mesas; lays bedrock over the cliffs.
sand_shadow	Sand shadows: a tapering sand tail in the lee of each boulder of the nearest boulder layer before this one; lays sand over the material map.