FractalGenerator.lua

--[[
    Created by michlbro#0414

    USAGE:

    local FractalGenerator = require(<path to this module>)
    local fractal = FractalGenerator.new(seed: number?, fractalProperties: table?)

    fractalProperties = {
      amplitude = number?,
	    frequency = number?,
	    lacunarity = number?,
	    persistence = number?,
	    octaves = number?
    }

    fractal:GenerateNoise(x: number, y: number?, z: number?): number [-amplitude, amplitude] (I'd probably still clamp it between the +- amplitudes.)
]]
--!strict

export type fractalProperties = {
	amplitude: number?,
	frequency: number?,
	lacunarity: number?,
	persistence: number?,
	octaves: number?
}

local fractalGenerator = {}

function fractalGenerator:GenerateNoise(xCord: number, yCord: number?, zCord: number?): number
	local lacunarity = self.lacunarity
	local persistence = self.persistence
	local seed = self.seed

	local noiseValue = self.amplitude
	local tempAmplitude = self.amplitude
	local tempFrequency = self.frequency

	for _ = 1, self.octaves do
		local x = xCord * tempFrequency + seed
		local y = (yCord or 0) * tempFrequency + seed
		local z = (zCord or 0) * tempFrequency + seed
		noiseValue += math.noise(x, y, z) * tempAmplitude
		tempFrequency *= lacunarity
		tempAmplitude *= persistence
	end
	return noiseValue
end

local defaultProperties: fractalProperties = {
	amplitude = 1,
	frequency = 0.05,
	octaves = 4,
	lacunarity = 2.0,
	persistence = 0.5
}

local function new(seed: number?, fractalProperties: fractalProperties?)
	local newFractal = setmetatable({
		seed = seed or (Random.new():NextNumber()),
		amplitude = fractalProperties and fractalProperties.amplitude or defaultProperties.amplitude,
		frequency = fractalProperties and fractalProperties.frequency or defaultProperties.frequency,
		lacunarity = fractalProperties and fractalProperties.lacunarity or defaultProperties.lacunarity,
		persistence = fractalProperties and fractalProperties.persistence or defaultProperties.persistence,
		octaves = fractalProperties and fractalProperties.octaves or defaultProperties.octaves
	},{
		__index = fractalGenerator
	})
	return newFractal
end

return setmetatable({new = new}, {__index = fractalGenerator})