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https://github.com/bevyengine/bevy
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d39ab55b61
# Objective - Fixes #12544 ## Solution - Added/updated a universally worded comment to all seeded rng instances in our examples.
80 lines
2.9 KiB
Rust
80 lines
2.9 KiB
Rust
//! Illustrates parallel queries with `ParallelIterator`.
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use bevy::ecs::query::BatchingStrategy;
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use bevy::prelude::*;
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use rand::{Rng, SeedableRng};
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use rand_chacha::ChaCha8Rng;
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#[derive(Component, Deref)]
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struct Velocity(Vec2);
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fn spawn_system(mut commands: Commands, asset_server: Res<AssetServer>) {
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commands.spawn(Camera2dBundle::default());
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let texture = asset_server.load("branding/icon.png");
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// We're seeding the PRNG here to make this example deterministic for testing purposes.
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// This isn't strictly required in practical use unless you need your app to be deterministic.
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let mut rng = ChaCha8Rng::seed_from_u64(19878367467713);
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for _ in 0..128 {
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commands.spawn((
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SpriteBundle {
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texture: texture.clone(),
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transform: Transform::from_scale(Vec3::splat(0.1)),
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..default()
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},
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Velocity(20.0 * Vec2::new(rng.gen::<f32>() - 0.5, rng.gen::<f32>() - 0.5)),
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));
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}
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}
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// Move sprites according to their velocity
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fn move_system(mut sprites: Query<(&mut Transform, &Velocity)>) {
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// Compute the new location of each sprite in parallel on the
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// ComputeTaskPool
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//
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// This example is only for demonstrative purposes. Using a
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// ParallelIterator for an inexpensive operation like addition on only 128
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// elements will not typically be faster than just using a normal Iterator.
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// See the ParallelIterator documentation for more information on when
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// to use or not use ParallelIterator over a normal Iterator.
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sprites
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.par_iter_mut()
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.for_each(|(mut transform, velocity)| {
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transform.translation += velocity.extend(0.0);
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});
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}
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// Bounce sprites outside the window
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fn bounce_system(windows: Query<&Window>, mut sprites: Query<(&Transform, &mut Velocity)>) {
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let window = windows.single();
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let width = window.width();
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let height = window.height();
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let left = width / -2.0;
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let right = width / 2.0;
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let bottom = height / -2.0;
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let top = height / 2.0;
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// The default batch size can also be overridden.
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// In this case a batch size of 32 is chosen to limit the overhead of
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// ParallelIterator, since negating a vector is very inexpensive.
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sprites
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.par_iter_mut()
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.batching_strategy(BatchingStrategy::fixed(32))
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.for_each(|(transform, mut v)| {
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if !(left < transform.translation.x
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&& transform.translation.x < right
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&& bottom < transform.translation.y
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&& transform.translation.y < top)
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{
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// For simplicity, just reverse the velocity; don't use realistic bounces
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v.0 = -v.0;
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}
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});
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}
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_systems(Startup, spawn_system)
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.add_systems(Update, (move_system, bounce_system))
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.run();
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}
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