Fresnelcut

Diffuser

2D Skyline Diffuser

A skyline diffuser is the block-city panel: a grid of square blocks at varying heights. It scatters in both axes like a 2-D QRD, but is built by folding a 1-D primitive-root sequence into a rectangular grid, giving every block a unique height.

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How it works

The block heights come from a primitive-root sequence `g^h mod N` folded onto an X×Y grid (where X·Y = N−1 and X, Y are coprime) using the Chinese-Remainder-Theorem mapping. Because every height is unique, the specular lobe is suppressed on both axes — the 2-D analogue of what a PRD does in one axis.

Skylines are popular because they are visually striking and machine-friendly: each block is a simple rectangular prism, easy to CNC or stack from sheet stock.

The math
S_h = g^h mod N → grid cell (h mod X, h mod Y)

CRT folding of the 1-D primitive-root sequence. N−1 = X·Y with gcd(X,Y)=1, so the array is never square.

Best for

  • A statement wall that also treats reflections
  • Two-axis scatter with the block-city aesthetic

Not the tool for

  • Low-frequency control (use an absorber)
  • The thinnest possible panel — tall blocks need depth

Start from a common size

N is the number of wells (a prime). More wells scatter more smoothly but make a wider, deeper panel. Pick one to open the designer pre-set:

Related reading

Related panel types

See all diffuser & absorber types.