ludic/docs/language/noise/noise-unit.md
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feat(stdlib): add Noise.* — deterministic fixed-point procedural noise (#3)
A Noise.* namespace for procedural generation, implemented entirely in Q16.16
fixed point over an integer permutation hash so a seed reproduces the exact same
field on every platform and run (native/headless/wasm) — the determinism edge
over float noise that drifts across CPUs.

  - value2 / perlin2 / simplex2  — value, gradient, and simplex noise -> [-1,1]
  - fbm2(x,y,seed,octaves)       — fractal Brownian motion (octaves of simplex)
  - cellular2 / cellular2_id     — Worley F1 distance + nearest-cell id
  - unit(n)                      — remap [-1,1] -> [0,1]

Covers issue phases 1–2 fully plus cellular from phase 3; domain warp, ridged/
billow, and sample1/sample3 remain as follow-ups. Pure integer IR, C-free;
cellular/fbm reuse the math prelude's fx_sqrt.

- examples/library/noise.ludic: asserts the invariants a fixed-point generator
  must hold (Perlin == 0 at lattice points, every sampler within [-1,1],
  reproducibility, seed sensitivity, non-negative cellular distance). Wired into
  `x test` (now 52 passed).
- docs: a new Noise section + per-symbol pages; inventory and coverage pass.
- seed regenerated; `x bootstrap-cfree` fixpoint holds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-08-30 21:50:50 +03:00

997 B

id name category kind tokens sig tip order ns member
noise-unit Noise.unit noise namespace-method Noise.unit Noise.unit(n) -> fixed Remap a [-1,1] noise sample to [0,1]. 7 Noise unit

Remaps a noise sample from [-1, 1] to [0, 1] — literally n / 2 + 0.5 — returning a fixed. The signed range is the natural output of the samplers, but heights, densities, probabilities, and colour ramps usually want the unsigned [0, 1] range; unit is the one-step conversion. It is a plain affine remap, so unit(-1) == 0, unit(0) == 0.5, and unit(1) == 1.

Parameters:

  • n — a sample in [-1, 1] (e.g. from perlin2/simplex2/fbm2)
program Unit {
  entry {
    let n = Noise.simplex2(fixed(1) / fixed(2), fixed(1) / fixed(2), 1337)
    let height = Math.floor(Noise.unit(n) * fixed(64))   # 0..64 tiles
    print(height)
  }
}