81b53d15d4
Resolves #1253 #1562 This makes the Commands apis consistent with World apis. This moves to a "type state" pattern (like World) where the "current entity" is stored in an `EntityCommands` builder. In general this tends to cuts down on indentation and line count. It comes at the cost of needing to type `commands` more and adding more semicolons to terminate expressions. I also added `spawn_bundle` to Commands because this is a common enough operation that I think its worth providing a shorthand.
78 lines
2.7 KiB
Rust
78 lines
2.7 KiB
Rust
use bevy::{prelude::*, tasks::prelude::*};
|
|
use rand::random;
|
|
|
|
struct Velocity(Vec2);
|
|
|
|
fn spawn_system(
|
|
mut commands: Commands,
|
|
asset_server: Res<AssetServer>,
|
|
mut materials: ResMut<Assets<ColorMaterial>>,
|
|
) {
|
|
commands.spawn_bundle(OrthographicCameraBundle::new_2d());
|
|
let texture_handle = asset_server.load("branding/icon.png");
|
|
let material = materials.add(texture_handle.into());
|
|
for _ in 0..128 {
|
|
commands
|
|
.spawn_bundle(SpriteBundle {
|
|
material: material.clone(),
|
|
transform: Transform::from_scale(Vec3::splat(0.1)),
|
|
..Default::default()
|
|
})
|
|
.insert(Velocity(
|
|
20.0 * Vec2::new(random::<f32>() - 0.5, random::<f32>() - 0.5),
|
|
));
|
|
}
|
|
}
|
|
|
|
// Move sprites according to their velocity
|
|
fn move_system(pool: Res<ComputeTaskPool>, mut sprites: Query<(&mut Transform, &Velocity)>) {
|
|
// Compute the new location of each sprite in parallel on the
|
|
// ComputeTaskPool using batches of 32 sprites
|
|
//
|
|
// 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_for_each_mut(&pool, 32, |(mut transform, velocity)| {
|
|
transform.translation += velocity.0.extend(0.0);
|
|
});
|
|
}
|
|
|
|
// Bounce sprites outside the window
|
|
fn bounce_system(
|
|
pool: Res<ComputeTaskPool>,
|
|
windows: Res<Windows>,
|
|
mut sprites: Query<(&Transform, &mut Velocity)>,
|
|
) {
|
|
let window = windows.get_primary().expect("No primary window.");
|
|
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;
|
|
sprites
|
|
// Batch size of 32 is chosen to limit the overhead of
|
|
// ParallelIterator, since negating a vector is very inexpensive.
|
|
.par_for_each_mut(&pool, 32, |(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::build()
|
|
.add_plugins(DefaultPlugins)
|
|
.add_startup_system(spawn_system.system())
|
|
.add_system(move_system.system())
|
|
.add_system(bounce_system.system())
|
|
.run();
|
|
}
|