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use crate::math;
use crate::noise_fns::{MultiFractal, NoiseFn, Perlin, Seedable};
/// Noise function that outputs hybrid Multifractal noise.
///
/// The result of this multifractal noise is that valleys in the noise should
/// have smooth bottoms at all altitudes.
#[derive(Clone, Debug)]
pub struct HybridMulti {
/// Total number of frequency octaves to generate the noise with.
///
/// The number of octaves control the _amount of detail_ in the noise
/// function. Adding more octaves increases the detail, with the drawback
/// of increasing the calculation time.
pub octaves: usize,
/// The number of cycles per unit length that the noise function outputs.
pub frequency: f64,
/// A multiplier that determines how quickly the frequency increases for
/// each successive octave in the noise function.
///
/// The frequency of each successive octave is equal to the product of the
/// previous octave's frequency and the lacunarity value.
///
/// A lacunarity of 2.0 results in the frequency doubling every octave. For
/// almost all cases, 2.0 is a good value to use.
pub lacunarity: f64,
/// A multiplier that determines how quickly the amplitudes diminish for
/// each successive octave in the noise function.
///
/// The amplitude of each successive octave is equal to the product of the
/// previous octave's amplitude and the persistence value. Increasing the
/// persistence produces "rougher" noise.
pub persistence: f64,
seed: u32,
sources: Vec<Perlin>,
}
impl HybridMulti {
pub const DEFAULT_SEED: u32 = 0;
pub const DEFAULT_OCTAVES: usize = 6;
pub const DEFAULT_FREQUENCY: f64 = 2.0;
pub const DEFAULT_LACUNARITY: f64 = std::f64::consts::PI * 2.0 / 3.0;
pub const DEFAULT_PERSISTENCE: f64 = 0.25;
pub const MAX_OCTAVES: usize = 32;
pub fn new() -> Self {
Self {
seed: Self::DEFAULT_SEED,
octaves: Self::DEFAULT_OCTAVES,
frequency: Self::DEFAULT_FREQUENCY,
lacunarity: Self::DEFAULT_LACUNARITY,
persistence: Self::DEFAULT_PERSISTENCE,
sources: super::build_sources(Self::DEFAULT_SEED, Self::DEFAULT_OCTAVES),
}
}
}
impl Default for HybridMulti {
fn default() -> Self {
Self::new()
}
}
impl MultiFractal for HybridMulti {
fn set_octaves(self, mut octaves: usize) -> Self {
if self.octaves == octaves {
return self;
}
octaves = math::clamp(octaves, 1, Self::MAX_OCTAVES);
Self {
octaves,
sources: super::build_sources(self.seed, octaves),
..self
}
}
fn set_frequency(self, frequency: f64) -> Self {
Self { frequency, ..self }
}
fn set_lacunarity(self, lacunarity: f64) -> Self {
Self { lacunarity, ..self }
}
fn set_persistence(self, persistence: f64) -> Self {
Self {
persistence,
..self
}
}
}
impl Seedable for HybridMulti {
fn set_seed(self, seed: u32) -> Self {
if self.seed == seed {
return self;
}
Self {
seed,
sources: super::build_sources(seed, self.octaves),
..self
}
}
fn seed(&self) -> u32 {
self.seed
}
}
/// 2-dimensional `HybridMulti` noise
impl NoiseFn<[f64; 2]> for HybridMulti {
fn get(&self, mut point: [f64; 2]) -> f64 {
// First unscaled octave of function; later octaves are scaled.
point = math::mul2(point, self.frequency);
let mut result = self.sources[0].get(point) * self.persistence;
let mut weight = result;
// Spectral construction inner loop, where the fractal is built.
for x in 1..self.octaves {
// Prevent divergence.
weight = weight.max(1.0);
// Raise the spatial frequency.
point = math::mul2(point, self.lacunarity);
// Get noise value.
let mut signal = self.sources[x].get(point);
// Scale the amplitude appropriately for this frequency.
signal *= self.persistence.powi(x as i32);
// Add it in, weighted by previous octave's noise value.
result += weight * signal;
// Update the weighting value.
weight *= signal;
}
// Scale the result to the [-1,1] range
result * 3.0
}
}
/// 3-dimensional `HybridMulti` noise
impl NoiseFn<[f64; 3]> for HybridMulti {
fn get(&self, mut point: [f64; 3]) -> f64 {
// First unscaled octave of function; later octaves are scaled.
point = math::mul3(point, self.frequency);
let mut result = self.sources[0].get(point) * self.persistence;
let mut weight = result;
// Spectral construction inner loop, where the fractal is built.
for x in 1..self.octaves {
// Prevent divergence.
weight = weight.max(1.0);
// Raise the spatial frequency.
point = math::mul3(point, self.lacunarity);
// Get noise value.
let mut signal = self.sources[x].get(point);
// Scale the amplitude appropriately for this frequency.
signal *= self.persistence.powi(x as i32);
// Add it in, weighted by previous octave's noise value.
result += weight * signal;
// Update the weighting value.
weight *= signal;
}
// Scale the result to the [-1,1] range
result * 3.0
}
}
/// 4-dimensional `HybridMulti` noise
impl NoiseFn<[f64; 4]> for HybridMulti {
fn get(&self, mut point: [f64; 4]) -> f64 {
// First unscaled octave of function; later octaves are scaled.
point = math::mul4(point, self.frequency);
let mut result = self.sources[0].get(point) * self.persistence;
let mut weight = result;
// Spectral construction inner loop, where the fractal is built.
for x in 1..self.octaves {
// Prevent divergence.
weight = weight.max(1.0);
// Raise the spatial frequency.
point = math::mul4(point, self.lacunarity);
// Get noise value.
let mut signal = self.sources[x].get(point);
// Scale the amplitude appropriately for this frequency.
signal *= self.persistence.powi(x as i32);
// Add it in, weighted by previous octave's noise value.
result += weight * signal;
// Update the weighting value.
weight *= signal;
}
// Scale the result to the [-1,1] range
result * 3.0
}
}