fbm/fbm

(no submodules)

Purpose

The fbm module composes Fractional Brownian Motion on top of any base noise function. It layers octaves copies of the base at geometrically increasing frequencies (lacunarity) and geometrically decreasing amplitudes (gain), yielding the classical cloud/terrain/texture multi-scale roughness pattern that underlies most procedurally generated content.

Because fbm2/fbm3 take the base function as a parameter, you can layer any of perlin2, simplex2, value2, or even Worley distances on top of fBm — the module has no coupling to a specific noise kind.

Features

fbm2(base, x, y, opts?) — 2D compositor
fbm3(base, x, y, z, opts?) — 3D compositor
Configurable octaves, lacunarity, gain, frequency, amplitude
Argument validation via NoiseError.ARG.INVALID / FBM.INVALID_OCTAVES

Usage: Basic Example

import { fbm2, PerlinNoise } from "@suaveplan/noise";

const p = new PerlinNoise("world");
const h = fbm2((x, y) => p.noise2(x, y), 1.5, 2.3);

Usage: Advanced Example

import { fbm3, SimplexNoise } from "@suaveplan/noise";

const s = new SimplexNoise("clouds");
const v = fbm3(
  (x, y, z) => s.noise3(x, y, z),
  0.1, 0.2, 0.3,
  { octaves: 6, lacunarity: 2.0, gain: 0.5, frequency: 1, amplitude: 1 },
);

API Reference

FbmOptions — every field optional: octaves (default 4, must be an integer 1–32), lacunarity (default 2), gain (default 0.5, must be in (0, 1]), frequency (default 1), amplitude (default 1).
fbm2(base, x, y, opts?): number
fbm3(base, x, y, z, opts?): number

Implementation Notes

Clamping octaves to 1–32 avoids pathological input (negative or absurdly large numbers of loop iterations). gain > 1 would diverge rather than converge, so it's rejected; gain exactly 1 means every octave contributes equally, which is useful for certain stylised effects but rejected here to keep the numeric output bounded — if you need that, call the base function manually in a loop.

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