Example showing how to use AsyncComputeTaskPool and Tasks (#2180)

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the-notable 2021-05-23 20:13:55 +00:00
parent bec323e2e2
commit 9f94f7eb6c
3 changed files with 134 additions and 0 deletions

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@ -87,6 +87,8 @@ anyhow = "1.0"
rand = "0.8.0"
ron = "0.6.2"
serde = {version = "1", features = ["derive"]}
# Needed to poll Task examples
futures-lite = "1.11.3"
[[example]]
name = "hello_world"
@ -232,6 +234,11 @@ path = "examples/asset/custom_asset_io.rs"
name = "hot_asset_reloading"
path = "examples/asset/hot_asset_reloading.rs"
# Async Tasks
[[example]]
name = "async_compute"
path = "examples/async_tasks/async_compute.rs"
# Audio
[[example]]
name = "audio"

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@ -41,6 +41,7 @@ git checkout v0.4.0
- [3D Rendering](#3d-rendering)
- [Application](#application)
- [Assets](#assets)
- [Async Tasks](#async-tasks)
- [Audio](#audio)
- [Diagnostics](#diagnostics)
- [ECS (Entity Component System)](#ecs-entity-component-system)
@ -131,6 +132,12 @@ Example | File | Description
`custom_asset_io` | [`asset/custom_asset_io.rs`](./asset/custom_asset_io.rs) | Implements a custom asset io loader
`hot_asset_reloading` | [`asset/hot_asset_reloading.rs`](./asset/hot_asset_reloading.rs) | Demonstrates automatic reloading of assets when modified on disk
## Async Tasks
Example | File | Description
--- | --- | ---
`async_compute` | [`async_tasks/async_compute.rs`](async_tasks/async_compute.rs) | How to use `AsyncComputeTaskPool` to complete longer running tasks
## Audio
Example | File | Description

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@ -0,0 +1,120 @@
use bevy::{
prelude::*,
tasks::{AsyncComputeTaskPool, Task},
};
use futures_lite::future;
use rand::Rng;
use std::time::{Duration, Instant};
/// This example shows how to use the ECS and the AsyncComputeTaskPool
/// to spawn, poll, and complete tasks across systems and system ticks.
fn main() {
App::build()
.insert_resource(Msaa { samples: 4 })
.add_plugins(DefaultPlugins)
.add_startup_system(setup_env.system())
.add_startup_system(add_assets.system())
.add_startup_system(spawn_tasks.system())
.add_system(handle_tasks.system())
.run();
}
// Number of cubes to spawn across the x, y, and z axis
const NUM_CUBES: u32 = 6;
struct BoxMeshHandle(Handle<Mesh>);
struct BoxMaterialHandle(Handle<StandardMaterial>);
/// Startup system which runs only once and generates our Box Mesh
/// and Box Material assets, adds them to their respective Asset
/// Resources, and stores their handles as resources so we can access
/// them later when we're ready to render our Boxes
fn add_assets(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<StandardMaterial>>,
) {
let box_mesh_handle = meshes.add(Mesh::from(shape::Cube { size: 0.25 }));
commands.insert_resource(BoxMeshHandle(box_mesh_handle));
let box_material_handle = materials.add(Color::rgb(1.0, 0.2, 0.3).into());
commands.insert_resource(BoxMaterialHandle(box_material_handle));
}
/// This system generates tasks simulating computationally intensive
/// work that potentially spans multiple frames/ticks. A separate
/// system, handle_tasks, will poll the spawned tasks on subsequent
/// frames/ticks, and use the results to spawn cubes
fn spawn_tasks(mut commands: Commands, thread_pool: Res<AsyncComputeTaskPool>) {
for x in 0..NUM_CUBES {
for y in 0..NUM_CUBES {
for z in 0..NUM_CUBES {
// Spawn new task on the AsyncComputeTaskPool
let task = thread_pool.spawn(async move {
let mut rng = rand::thread_rng();
let start_time = Instant::now();
let duration = Duration::from_secs_f32(rng.gen_range(0.05..0.2));
while Instant::now() - start_time < duration {
// Spinning for 'duration', simulating doing hard
// compute work generating translation coords!
}
// Such hard work, all done!
Transform::from_translation(Vec3::new(x as f32, y as f32, z as f32))
});
// Spawn new entity and add our new task as a component
commands.spawn().insert(task);
}
}
}
}
/// This system queries for entities that have our Task<Transform> component. It polls the
/// tasks to see if they're complete. If the task is complete it takes the result, adds a
/// new PbrBundle of components to the entity using the result from the task's work, and
/// removes the task component from the entity.
fn handle_tasks(
mut commands: Commands,
mut transform_tasks: Query<(Entity, &mut Task<Transform>)>,
box_mesh_handle: Res<BoxMeshHandle>,
box_material_handle: Res<BoxMaterialHandle>,
) {
for (entity, mut task) in transform_tasks.iter_mut() {
if let Some(transform) = future::block_on(future::poll_once(&mut *task)) {
// Add our new PbrBundle of components to our tagged entity
commands.entity(entity).insert_bundle(PbrBundle {
mesh: box_mesh_handle.0.clone(),
material: box_material_handle.0.clone(),
transform,
..Default::default()
});
// Task is complete, so remove task component from entity
commands.entity(entity).remove::<Task<Transform>>();
}
}
}
/// This system is only used to setup light and camera for the environment
fn setup_env(mut commands: Commands) {
// Used to center camera on spawned cubes
let offset = if NUM_CUBES % 2 == 0 {
(NUM_CUBES / 2) as f32 - 0.5
} else {
(NUM_CUBES / 2) as f32
};
// lights
commands.spawn_bundle(PointLightBundle {
transform: Transform::from_translation(Vec3::new(4.0, 12.0, 15.0)),
..Default::default()
});
// camera
commands.spawn_bundle(PerspectiveCameraBundle {
transform: Transform::from_translation(Vec3::new(offset, offset, 15.0))
.looking_at(Vec3::new(offset, offset, 0.0), Vec3::Y),
..Default::default()
});
}