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extern crate rand;
use std::iter::{self, Extend};
use std::f64;
use rand::{Rng, StdRng, SeedableRng};
use std::collections::HashMap;
pub struct WorleyNoise {
permutation_x: Vec<usize>,
permutation_y: Vec<usize>,
permutation_mask: usize,
density: f64,
point_count_table: Vec<u32>,
cache: HashMap<(i32, i32), Vec<(f64, f64)>>,
distance_function: Box<FnMut(f64, f64) -> f64>,
value_function: Box<FnMut(Vec<f64>) -> f64>,
radius: u16
}
impl WorleyNoise {
const MIN_POINTS: u32 = 1;
const MAX_POINTS: u32 = 9;
const POINT_COUNT_TABLE_LEN: usize = 100;
const DEFAULT_RADIUS: u16 = 1;
const DEFAULT_PERMUTATION_BITS: usize = 8;
const DEFAULT_DENSITY: f64 = 3.0;
const DEFAULT_CACHE_CAPACITY: usize = 1000;
pub fn new() -> Self {
Self::with_cache_capacity(Self::DEFAULT_CACHE_CAPACITY)
}
pub fn with_cache_capacity(capacity: usize) -> Self {
let default_distance_function = |x, y| x * x + y * y;
let default_value_function = |distances: Vec<f64>| distances.iter()
.cloned()
.fold(f64::MAX, f64::min);
let mut noise = WorleyNoise {
permutation_x: Vec::new(),
permutation_y: Vec::new(),
permutation_mask: 0,
density: 0.0,
point_count_table: Vec::new(),
cache: HashMap::with_capacity(capacity),
distance_function: Box::new(default_distance_function),
value_function: Box::new(default_value_function),
radius: Self::DEFAULT_RADIUS
};
noise.set_density(Self::DEFAULT_DENSITY);
noise.permutate(Self::DEFAULT_PERMUTATION_BITS);
noise
}
fn feature_point_count(&self, probability: f64) -> u32 {
let index = ((self.point_count_table.len() - 1) as f64 * probability).floor() as usize;
self.point_count_table[index]
}
fn hash(&self, x: i32, y: i32) -> [usize; 1] {
let x = self.permutation_x[x as usize & self.permutation_mask];
let y = self.permutation_y[y as usize & self.permutation_mask];
[x ^ y]
}
fn feature_points(&mut self, quad_x: i32, quad_y: i32, collector: &mut Vec<(f64, f64)>) {
let created = if let Some(points) = self.cache.get(&(quad_x, quad_y)) {
collector.extend_from_slice(points);
None
} else {
let mut points = Vec::new();
let mut rng = StdRng::from_seed(&self.hash(quad_x, quad_y));
let count = self.feature_point_count(rng.next_f64());
for _ in 0 .. count {
let x = rng.next_f64() + quad_x as f64;
let y = rng.next_f64() + quad_y as f64;
points.push((x, y));
}
collector.extend_from_slice(&points);
Some(points)
};
if let Some(created) = created {
self.cache.insert((quad_x, quad_y), created);
}
}
fn adjacent_feature_points(&mut self, quad_x: i32, quad_y: i32) -> Vec<(f64, f64)> {
let mut points = Vec::with_capacity((self.density * 9.0) as usize);
let radius = self.radius as i32;
let start_x = quad_x - radius;
let start_y = quad_y - radius;
for x in start_x .. quad_x + radius + 1 {
for y in start_y .. quad_y + radius + 1 {
self.feature_points(x, y, &mut points);
}
}
points
}
pub fn permutate(&mut self, permutation_table_bit_length: usize) {
self.permutate_seeded(permutation_table_bit_length, rand::random());
}
pub fn permutate_seeded(&mut self, permutation_table_bit_length: usize, seed: usize) {
let mut rng = StdRng::from_seed(&[seed]);
let length = 1 << permutation_table_bit_length;
self.permutation_x.reserve(length);
self.permutation_y.reserve(length);
self.permutation_x.extend(rng.gen_iter::<usize>().take(length));
self.permutation_y.extend(rng.gen_iter::<usize>().take(length));
self.permutation_mask = length - 1;
}
pub fn set_density(&mut self, density: f64) {
self.point_count_table.clear();
self.point_count_table.reserve(Self::POINT_COUNT_TABLE_LEN);
for i in Self::MIN_POINTS .. Self::MAX_POINTS + 1 {
let poisson = density.powi(i as i32) / factorial(i as u16) as f64 * f64::consts::E.powf(-density);
let count = (poisson * Self::POINT_COUNT_TABLE_LEN as f64).round() as usize;
self.point_count_table.extend(iter::repeat(i).take(count));
}
}
pub fn set_distance_function<F>(&mut self, function: F) where F: FnMut(f64, f64) -> f64 + 'static {
self.distance_function = Box::new(function);
}
pub fn set_value_function<F>(&mut self, function: F) where F: FnMut(Vec<f64>) -> f64 + 'static {
self.value_function = Box::new(function);
}
pub fn set_radius(&mut self, radius: u16) {
self.radius = radius;
}
pub fn value(&mut self, x: f64, y: f64) -> f64 {
let quad_x = x.floor() as i32;
let quad_y = y.floor() as i32;
let points = self.adjacent_feature_points(quad_x, quad_y);
let distances = points.iter()
.map(|&(p_x, p_y)| (p_x - x, p_y - y))
.map(|(x, y)| (self.distance_function)(x, y))
.collect();
let val = (self.value_function)(distances);
val
}
}
fn factorial(x: u16) -> u32 {
let mut val = 1;
for i in 2 .. x as u32 + 1 {
val *= i;
}
val
}