Layered wind-anisotropic noise

Isotropic fBm is “blobby.” Real dunes are stretched, sheared, and stacked by scale under a prevailing wind.

SNOWFLOW · desert heightfield

How it works

Compose three layers with different frequencies and amplitudes:

Macro — broad ridges (tens of m)
Meso — drifts sheared along wind (metres)
Micro — sastrugi / ripples (dm), strongly anisotropic

For anisotropy, sample noise in a frame aligned to wind: p' = (dot(p, wind), dot(p, perp) * stretch) so features elongate across the wind and compress along it (or vice versa).

H = a₀ n(p/λ₀) + a₁ n(shear(p)/λ₁) + a₂ n(shear(p)/λ₂)

Prompt match

“Do not use a single fBm octave stack… Encode a wind direction and let the medium and fine layers stretch and shear along it.”

Controls

Modewind-sheared

Wind angle35°

Anisotropy (stretch)3.5

Micro ripples1.0

Compare: set mode to 0 for isotropic fBm — same frequencies, no wind frame. Structure collapses into generic noise.

Source prompts

SNOWFLOW waterbending · Desert explorer

Technique notes · All techniques

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layered dune field