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use crate::{
math::vectors::*,
noise_fns::{MultiFractal, NoiseFn, Seedable},
};
use alloc::vec::Vec;
/// 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<T> {
/// 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<T>,
scale_factor: f64,
}
impl<T> HybridMulti<T>
where
T: Default + Seedable,
{
pub const DEFAULT_SEED: u32 = 0;
pub const DEFAULT_OCTAVES: usize = 6;
pub const DEFAULT_FREQUENCY: f64 = 2.0;
pub const DEFAULT_LACUNARITY: f64 = core::f64::consts::PI * 2.0 / 3.0;
pub const DEFAULT_PERSISTENCE: f64 = 0.25;
pub const MAX_OCTAVES: usize = 32;
pub fn new(seed: u32) -> Self {
Self {
seed,
octaves: Self::DEFAULT_OCTAVES,
frequency: Self::DEFAULT_FREQUENCY,
lacunarity: Self::DEFAULT_LACUNARITY,
persistence: Self::DEFAULT_PERSISTENCE,
sources: super::build_sources(seed, Self::DEFAULT_OCTAVES),
scale_factor: Self::calc_scale_factor(Self::DEFAULT_PERSISTENCE, Self::DEFAULT_OCTAVES),
}
}
pub fn set_sources(self, sources: Vec<T>) -> Self {
Self { sources, ..self }
}
fn calc_scale_factor(persistence: f64, octaves: usize) -> f64 {
let mut result = persistence;
// Do octave 0
let mut amplitude = persistence;
let mut weight = result;
let mut signal = amplitude;
weight *= signal;
result += signal;
if octaves >= 1 {
result += (1..=octaves).fold(0.0, |acc, _| {
amplitude *= persistence;
weight = weight.max(1.0);
signal = amplitude;
weight *= signal;
acc + signal
});
}
2.0 / result
}
}
impl<T> Default for HybridMulti<T>
where
T: Default + Seedable,
{
fn default() -> Self {
Self::new(Self::DEFAULT_SEED)
}
}
impl<T> MultiFractal for HybridMulti<T>
where
T: Default + Seedable,
{
fn set_octaves(self, mut octaves: usize) -> Self {
if self.octaves == octaves {
return self;
}
octaves = octaves.clamp(1, Self::MAX_OCTAVES);
Self {
octaves,
sources: super::build_sources(self.seed, octaves),
scale_factor: Self::calc_scale_factor(self.persistence, 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,
scale_factor: Self::calc_scale_factor(persistence, self.octaves),
..self
}
}
}
impl<T> Seedable for HybridMulti<T>
where
T: Default + Seedable,
{
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<T> NoiseFn<f64, 2> for HybridMulti<T>
where
T: NoiseFn<f64, 2>,
{
fn get(&self, point: [f64; 2]) -> f64 {
let mut point = Vector2::from(point);
let mut attenuation = self.persistence;
// First unscaled octave of function; later octaves are scaled.
point *= self.frequency;
let mut result = self.sources[0].get(point.into_array()) * 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 *= self.lacunarity;
// Get noise value.
let mut signal = self.sources[x].get(point.into_array());
// Scale the amplitude appropriately for this frequency.
signal *= attenuation;
// Increase the attenuation for the next octave, to be equal to persistence ^ (x + 1)
attenuation *= self.persistence;
// 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 * self.scale_factor
}
}
/// 3-dimensional `HybridMulti` noise
impl<T> NoiseFn<f64, 3> for HybridMulti<T>
where
T: NoiseFn<f64, 3>,
{
fn get(&self, point: [f64; 3]) -> f64 {
let mut point = Vector3::from(point);
let mut attenuation = self.persistence;
// First unscaled octave of function; later octaves are scaled.
point *= self.frequency;
let mut result = self.sources[0].get(point.into_array()) * 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 *= self.lacunarity;
// Get noise value.
let mut signal = self.sources[x].get(point.into_array());
// Scale the amplitude appropriately for this frequency.
signal *= attenuation;
// Increase the attenuation for the next octave, to be equal to persistence ^ (x + 1)
attenuation *= self.persistence;
// 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 * self.scale_factor
}
}
/// 4-dimensional `HybridMulti` noise
impl<T> NoiseFn<f64, 4> for HybridMulti<T>
where
T: NoiseFn<f64, 4>,
{
fn get(&self, point: [f64; 4]) -> f64 {
let mut point = Vector4::from(point);
let mut attenuation = self.persistence;
// First unscaled octave of function; later octaves are scaled.
point *= self.frequency;
let mut result = self.sources[0].get(point.into_array()) * 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 *= self.lacunarity;
// Get noise value.
let mut signal = self.sources[x].get(point.into_array());
// Scale the amplitude appropriately for this frequency.
signal *= attenuation;
// Increase the attenuation for the next octave, to be equal to persistence ^ (x + 1)
attenuation *= self.persistence;
// 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 * self.scale_factor
}
}