b09f3bdfe6
# Objective Fixes issue #12613 - the RNG used in examples is _deterministic_, but its implementation is not _portable_ across platforms. We want to switch to using a portable RNG that does not vary across platforms, to ensure certain examples play out the same way every time. ## Solution Replace all occurences of `rand::rngs::StdRng` with `rand_chacha::ChaCha8Rng`, as recommended in issue #12613 --- ## Changelog - Add `rand_chacha` as a new dependency (controversial?) - Replace all occurences of `rand::rngs::StdRng` with `rand_chacha::ChaCha8Rng`
78 lines
2.7 KiB
Rust
78 lines
2.7 KiB
Rust
//! Illustrates parallel queries with `ParallelIterator`.
|
|
|
|
use bevy::ecs::query::BatchingStrategy;
|
|
use bevy::prelude::*;
|
|
use rand::{Rng, SeedableRng};
|
|
use rand_chacha::ChaCha8Rng;
|
|
|
|
#[derive(Component, Deref)]
|
|
struct Velocity(Vec2);
|
|
|
|
fn spawn_system(mut commands: Commands, asset_server: Res<AssetServer>) {
|
|
commands.spawn(Camera2dBundle::default());
|
|
let texture = asset_server.load("branding/icon.png");
|
|
let mut rng = ChaCha8Rng::seed_from_u64(19878367467713);
|
|
for _ in 0..128 {
|
|
commands.spawn((
|
|
SpriteBundle {
|
|
texture: texture.clone(),
|
|
transform: Transform::from_scale(Vec3::splat(0.1)),
|
|
..default()
|
|
},
|
|
Velocity(20.0 * Vec2::new(rng.gen::<f32>() - 0.5, rng.gen::<f32>() - 0.5)),
|
|
));
|
|
}
|
|
}
|
|
|
|
// Move sprites according to their velocity
|
|
fn move_system(mut sprites: Query<(&mut Transform, &Velocity)>) {
|
|
// Compute the new location of each sprite in parallel on the
|
|
// ComputeTaskPool
|
|
//
|
|
// This example is only for demonstrative purposes. Using a
|
|
// ParallelIterator for an inexpensive operation like addition on only 128
|
|
// elements will not typically be faster than just using a normal Iterator.
|
|
// See the ParallelIterator documentation for more information on when
|
|
// to use or not use ParallelIterator over a normal Iterator.
|
|
sprites
|
|
.par_iter_mut()
|
|
.for_each(|(mut transform, velocity)| {
|
|
transform.translation += velocity.extend(0.0);
|
|
});
|
|
}
|
|
|
|
// Bounce sprites outside the window
|
|
fn bounce_system(windows: Query<&Window>, mut sprites: Query<(&Transform, &mut Velocity)>) {
|
|
let window = windows.single();
|
|
let width = window.width();
|
|
let height = window.height();
|
|
let left = width / -2.0;
|
|
let right = width / 2.0;
|
|
let bottom = height / -2.0;
|
|
let top = height / 2.0;
|
|
// The default batch size can also be overridden.
|
|
// In this case a batch size of 32 is chosen to limit the overhead of
|
|
// ParallelIterator, since negating a vector is very inexpensive.
|
|
sprites
|
|
.par_iter_mut()
|
|
.batching_strategy(BatchingStrategy::fixed(32))
|
|
.for_each(|(transform, mut v)| {
|
|
if !(left < transform.translation.x
|
|
&& transform.translation.x < right
|
|
&& bottom < transform.translation.y
|
|
&& transform.translation.y < top)
|
|
{
|
|
// For simplicity, just reverse the velocity; don't use realistic bounces
|
|
v.0 = -v.0;
|
|
}
|
|
});
|
|
}
|
|
|
|
fn main() {
|
|
App::new()
|
|
.add_plugins(DefaultPlugins)
|
|
.add_systems(Startup, spawn_system)
|
|
.add_systems(Update, (move_system, bounce_system))
|
|
.run();
|
|
}
|