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Example showing how to use AsyncComputeTaskPool and Tasks (#2180)
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@ -87,6 +87,8 @@ anyhow = "1.0"
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rand = "0.8.0"
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ron = "0.6.2"
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serde = {version = "1", features = ["derive"]}
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# Needed to poll Task examples
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futures-lite = "1.11.3"
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[[example]]
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name = "hello_world"
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@ -232,6 +234,11 @@ path = "examples/asset/custom_asset_io.rs"
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name = "hot_asset_reloading"
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path = "examples/asset/hot_asset_reloading.rs"
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# Async Tasks
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[[example]]
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name = "async_compute"
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path = "examples/async_tasks/async_compute.rs"
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# Audio
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[[example]]
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name = "audio"
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@ -41,6 +41,7 @@ git checkout v0.4.0
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- [3D Rendering](#3d-rendering)
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- [Application](#application)
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- [Assets](#assets)
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- [Async Tasks](#async-tasks)
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- [Audio](#audio)
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- [Diagnostics](#diagnostics)
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- [ECS (Entity Component System)](#ecs-entity-component-system)
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@ -131,6 +132,12 @@ Example | File | Description
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`custom_asset_io` | [`asset/custom_asset_io.rs`](./asset/custom_asset_io.rs) | Implements a custom asset io loader
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`hot_asset_reloading` | [`asset/hot_asset_reloading.rs`](./asset/hot_asset_reloading.rs) | Demonstrates automatic reloading of assets when modified on disk
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## Async Tasks
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Example | File | Description
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--- | --- | ---
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`async_compute` | [`async_tasks/async_compute.rs`](async_tasks/async_compute.rs) | How to use `AsyncComputeTaskPool` to complete longer running tasks
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## Audio
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Example | File | Description
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120
examples/async_tasks/async_compute.rs
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120
examples/async_tasks/async_compute.rs
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@ -0,0 +1,120 @@
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use bevy::{
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prelude::*,
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tasks::{AsyncComputeTaskPool, Task},
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};
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use futures_lite::future;
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use rand::Rng;
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use std::time::{Duration, Instant};
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/// This example shows how to use the ECS and the AsyncComputeTaskPool
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/// to spawn, poll, and complete tasks across systems and system ticks.
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fn main() {
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App::build()
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.insert_resource(Msaa { samples: 4 })
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup_env.system())
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.add_startup_system(add_assets.system())
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.add_startup_system(spawn_tasks.system())
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.add_system(handle_tasks.system())
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.run();
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}
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// Number of cubes to spawn across the x, y, and z axis
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const NUM_CUBES: u32 = 6;
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struct BoxMeshHandle(Handle<Mesh>);
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struct BoxMaterialHandle(Handle<StandardMaterial>);
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/// Startup system which runs only once and generates our Box Mesh
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/// and Box Material assets, adds them to their respective Asset
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/// Resources, and stores their handles as resources so we can access
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/// them later when we're ready to render our Boxes
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fn add_assets(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<StandardMaterial>>,
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) {
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let box_mesh_handle = meshes.add(Mesh::from(shape::Cube { size: 0.25 }));
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commands.insert_resource(BoxMeshHandle(box_mesh_handle));
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let box_material_handle = materials.add(Color::rgb(1.0, 0.2, 0.3).into());
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commands.insert_resource(BoxMaterialHandle(box_material_handle));
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}
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/// This system generates tasks simulating computationally intensive
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/// work that potentially spans multiple frames/ticks. A separate
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/// system, handle_tasks, will poll the spawned tasks on subsequent
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/// frames/ticks, and use the results to spawn cubes
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fn spawn_tasks(mut commands: Commands, thread_pool: Res<AsyncComputeTaskPool>) {
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for x in 0..NUM_CUBES {
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for y in 0..NUM_CUBES {
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for z in 0..NUM_CUBES {
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// Spawn new task on the AsyncComputeTaskPool
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let task = thread_pool.spawn(async move {
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let mut rng = rand::thread_rng();
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let start_time = Instant::now();
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let duration = Duration::from_secs_f32(rng.gen_range(0.05..0.2));
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while Instant::now() - start_time < duration {
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// Spinning for 'duration', simulating doing hard
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// compute work generating translation coords!
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}
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// Such hard work, all done!
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Transform::from_translation(Vec3::new(x as f32, y as f32, z as f32))
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});
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// Spawn new entity and add our new task as a component
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commands.spawn().insert(task);
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}
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}
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}
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}
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/// This system queries for entities that have our Task<Transform> component. It polls the
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/// tasks to see if they're complete. If the task is complete it takes the result, adds a
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/// new PbrBundle of components to the entity using the result from the task's work, and
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/// removes the task component from the entity.
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fn handle_tasks(
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mut commands: Commands,
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mut transform_tasks: Query<(Entity, &mut Task<Transform>)>,
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box_mesh_handle: Res<BoxMeshHandle>,
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box_material_handle: Res<BoxMaterialHandle>,
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) {
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for (entity, mut task) in transform_tasks.iter_mut() {
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if let Some(transform) = future::block_on(future::poll_once(&mut *task)) {
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// Add our new PbrBundle of components to our tagged entity
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commands.entity(entity).insert_bundle(PbrBundle {
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mesh: box_mesh_handle.0.clone(),
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material: box_material_handle.0.clone(),
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transform,
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..Default::default()
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});
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// Task is complete, so remove task component from entity
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commands.entity(entity).remove::<Task<Transform>>();
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}
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}
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}
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/// This system is only used to setup light and camera for the environment
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fn setup_env(mut commands: Commands) {
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// Used to center camera on spawned cubes
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let offset = if NUM_CUBES % 2 == 0 {
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(NUM_CUBES / 2) as f32 - 0.5
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} else {
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(NUM_CUBES / 2) as f32
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};
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// lights
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commands.spawn_bundle(PointLightBundle {
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transform: Transform::from_translation(Vec3::new(4.0, 12.0, 15.0)),
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..Default::default()
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});
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// camera
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commands.spawn_bundle(PerspectiveCameraBundle {
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transform: Transform::from_translation(Vec3::new(offset, offset, 15.0))
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.looking_at(Vec3::new(offset, offset, 0.0), Vec3::Y),
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..Default::default()
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});
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}
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