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use glam::Vec2;
use rand::distributions::Uniform;
use rand::Rng;
use rand_distr::StandardNormal;
use sphere::sphere_volume;
use crate::algorithm::{Algorithm, Creator};
use crate::utils::*;
use crate::Builder;
#[derive(Debug, Clone, Copy)]
pub struct Bridson;
impl Creator for Bridson {
type Algo = Algo;
fn create(poisson: &Builder) -> Self::Algo {
Algo {
grid: Grid::new(poisson.radius, poisson.poisson_type),
active_samples: vec![],
outside: vec![],
success: 0,
}
}
}
pub struct Algo {
grid: Grid,
active_samples: Vec<Vec2>,
outside: Vec<Vec2>,
success: usize,
}
impl Algorithm for Algo {
fn next<R>(&mut self, poisson: &mut Builder, rng: &mut R) -> Option<mint::Vector2<f32>>
where
R: Rng,
{
while !self.active_samples.is_empty() {
let index = rng.sample(Uniform::new(0, self.active_samples.len()));
let cur = self.active_samples[index].clone();
for _ in 0..30 {
let min = 2.0 * poisson.radius;
let max = 4.0 * poisson.radius;
let sample = cur.clone() + random_point_annulus(rng, min, max).into();
if (0..2)
.map(|n| sample[n])
.all(|c| 0.0 <= c && c < 1.0)
{
let index = sample_to_index(&sample, self.grid.side());
if self.insert_if_valid(poisson, index, sample.clone()) {
return Some(sample.into());
}
}
}
self.active_samples.swap_remove(index);
}
while self.success == 0 {
let cell = rng.sample(Uniform::new(0, self.grid.cells()));
let index: Vec2 = decode(cell, self.grid.side()).expect(
"Because we are decoding random index within grid \
this should work.",
);
let sample = choose_random_sample(rng, &self.grid, index.clone(), 0);
if self.insert_if_valid(poisson, index, sample.clone()) {
return Some(sample.into());
}
}
None
}
fn size_hint(&self, poisson: &Builder) -> (usize, Option<usize>) {
let upper = if self.grid.cells() > self.success {
self.grid.cells() - self.success
} else {
0
};
let spacing = self.grid.cell();
let grid_volume = (upper as f32) * spacing.powi(2);
let sphere_volume = sphere_volume(2.0 * poisson.radius, 2);
let lower: f32 = grid_volume / sphere_volume;
let mut lower = lower.floor() as usize;
if lower > 0 {
lower -= 1;
}
(lower, Some(upper))
}
fn restrict(&mut self, sample: mint::Vector2<f32>) {
let sample: Vec2 = sample.into();
self.success += 1;
let index = sample_to_index(&sample, self.grid.side());
if let Some(g) = self.grid.get_mut(index) {
g.push(sample);
} else {
self.outside.push(sample);
}
}
fn stays_legal(&self, poisson: &Builder, sample: mint::Vector2<f32>) -> bool {
let sample: Vec2 = sample.into();
let index = sample_to_index(&sample, self.grid.side());
is_disk_free(&self.grid, poisson, index, 0, sample.clone(), &self.outside)
}
}
impl Algo {
fn insert_if_valid(&mut self, poisson: &mut Builder, index: Vec2, sample: Vec2) -> bool {
if is_disk_free(
&self.grid,
poisson,
index.clone(),
0,
sample.clone(),
&self.outside,
) {
self.active_samples.push(sample.clone());
self.grid
.get_mut(index)
.expect("Because the sample is in [0, 1), indexing it should work.")
.push(sample);
self.success += 1;
true
} else {
false
}
}
}
fn random_point_annulus<R>(rand: &mut R, min: f32, max: f32) -> Vec2
where
R: Rng,
{
loop {
let mut result = Vec2::zero();
for n in 0..2 {
result[n] = rand.sample(StandardNormal);
}
let result = result.normalize() * rand.gen::<f32>() * max;
if result.length() >= min {
return result;
}
}
}
#[test]
fn random_point_annulus_does_not_generate_outside_annulus() {
use rand::{rngs::SmallRng, SeedableRng};
let mut rng = SmallRng::seed_from_u64(42);
for _ in 0..10000 {
let result = random_point_annulus(&mut rng, 1.0, 2.0);
assert!(result.length() >= 1.0);
assert!(result.length() <= 2.0);
}
}
#[test]
fn random_point_annulus_generates_all_quadrants() {
use rand::{rngs::SmallRng, SeedableRng};
let mut rng = SmallRng::seed_from_u64(42);
let (mut top_left, mut top_right, mut bottom_left, mut bottom_right) =
(false, false, false, false);
for _ in 0..10000 {
let result = random_point_annulus(&mut rng, 1.0, 2.0);
if result.y() < 0.0 {
if result.x() < 0.0 {
bottom_left = true;
} else {
bottom_right = true;
}
} else {
if result.x() < 0.0 {
top_left = true;
} else {
top_right = true;
}
}
}
assert!(top_left);
assert!(top_right);
assert!(bottom_left);
assert!(bottom_right);
}