84 lines
2.8 KiB
Rust
84 lines
2.8 KiB
Rust
use bevy::{prelude::*, tasks::prelude::*};
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use rand::random;
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struct Velocity(Vec2);
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fn spawn_system(
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mut commands: Commands,
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asset_server: Res<AssetServer>,
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mut materials: ResMut<Assets<ColorMaterial>>,
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) {
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commands.spawn(Camera2dComponents::default());
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let texture_handle = asset_server.load("branding/icon.png");
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let material = materials.add(texture_handle.into());
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for _ in 0..128 {
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commands
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.spawn(SpriteComponents {
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material: material.clone(),
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transform: Transform::from_scale(Vec3::splat(0.1)),
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..Default::default()
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})
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.with(Velocity(
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20.0 * Vec2::new(random::<f32>() - 0.5, random::<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(pool: Res<ComputeTaskPool>, 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 using batches of 32 sprties
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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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.iter()
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.par_iter(32)
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.for_each(&pool, |(mut transform, velocity)| {
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transform.translation += velocity.0.extend(0.0);
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});
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}
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// Bounce sprties outside the window
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fn bounce_system(
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pool: Res<ComputeTaskPool>,
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windows: Res<Windows>,
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mut sprites: Query<(&Transform, &mut Velocity)>,
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) {
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let window = windows.get_primary().expect("No primary window");
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let width = window.width();
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let height = window.height();
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let left = width as f32 / -2.0;
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let right = width as f32 / 2.0;
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let bottom = height as f32 / -2.0;
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let top = height as f32 / 2.0;
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sprites
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.iter()
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// 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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.par_iter(32)
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// Filter out sprites that don't need to be bounced
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.filter(|(transform, _)| {
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!(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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.for_each(&pool, |(_, mut v)| {
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v.0 = -v.0;
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});
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}
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fn main() {
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App::build()
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.add_default_plugins()
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.add_startup_system(spawn_system.system())
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.add_system(move_system.system())
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.add_system(bounce_system.system())
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.run();
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}
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