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Example time api (#10204)
# Objective - Fixes #10133 ## Solution - Add a new example that focuses on using `Virtual` time ## Changelog ### Added - new `virtual_time` example ### Changed - moved `time` & `timers` examples to the new `examples/time` folder
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5 changed files with 243 additions and 6 deletions
20
Cargo.toml
20
Cargo.toml
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@ -1420,27 +1420,39 @@ description = "Illustrates creating custom system parameters with `SystemParam`"
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category = "ECS (Entity Component System)"
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wasm = false
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# Time
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[[example]]
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name = "time"
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path = "examples/ecs/time.rs"
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path = "examples/time/time.rs"
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[package.metadata.example.time]
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name = "Time handling"
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description = "Explains how Time is handled in ECS"
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category = "ECS (Entity Component System)"
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category = "Time"
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wasm = false
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[[example]]
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name = "virtual_time"
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path = "examples/time/virtual_time.rs"
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[package.metadata.example.virtual_time]
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name = "Virtual time"
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description = "Shows how `Time<Virtual>` can be used to pause, resume, slow down and speed up a game."
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category = "Time"
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wasm = false
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[[example]]
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name = "timers"
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path = "examples/ecs/timers.rs"
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path = "examples/time/timers.rs"
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doc-scrape-examples = true
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[package.metadata.example.timers]
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name = "Timers"
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description = "Illustrates ticking `Timer` resources inside systems and handling their state"
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category = "ECS (Entity Component System)"
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category = "Time"
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wasm = false
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# Games
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[[example]]
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name = "alien_cake_addict"
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@ -53,6 +53,7 @@ git checkout v0.4.0
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- [Scene](#scene)
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- [Shaders](#shaders)
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- [Stress Tests](#stress-tests)
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- [Time](#time)
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- [Tools](#tools)
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- [Transforms](#transforms)
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- [UI (User Interface)](#ui-user-interface)
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@ -233,8 +234,6 @@ Example | Description
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[System Closure](../examples/ecs/system_closure.rs) | Show how to use closures as systems, and how to configure `Local` variables by capturing external state
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[System Parameter](../examples/ecs/system_param.rs) | Illustrates creating custom system parameters with `SystemParam`
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[System Piping](../examples/ecs/system_piping.rs) | Pipe the output of one system into a second, allowing you to handle any errors gracefully
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[Time handling](../examples/ecs/time.rs) | Explains how Time is handled in ECS
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[Timers](../examples/ecs/timers.rs) | Illustrates ticking `Timer` resources inside systems and handling their state
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## Games
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@ -326,6 +325,14 @@ Example | Description
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[Text Pipeline](../examples/stress_tests/text_pipeline.rs) | Text Pipeline benchmark
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[Transform Hierarchy](../examples/stress_tests/transform_hierarchy.rs) | Various test cases for hierarchy and transform propagation performance
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## Time
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Example | Description
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--- | ---
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[Time handling](../examples/time/time.rs) | Explains how Time is handled in ECS
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[Timers](../examples/time/timers.rs) | Illustrates ticking `Timer` resources inside systems and handling their state
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[Virtual time](../examples/time/virtual_time.rs) | Shows how `Time<Virtual>` can be used to pause, resume, slow down and speed up a game.
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## Tools
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Example | Description
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218
examples/time/virtual_time.rs
Normal file
218
examples/time/virtual_time.rs
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@ -0,0 +1,218 @@
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//! Shows how `Time<Virtual>` can be used to pause, resume, slow down
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//! and speed up a game.
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use std::time::Duration;
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use bevy::{
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input::common_conditions::input_just_pressed, prelude::*,
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time::common_conditions::on_real_timer,
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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, setup)
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.add_systems(
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Update,
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(
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move_virtual_time_sprites,
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move_real_time_sprites,
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toggle_pause.run_if(input_just_pressed(KeyCode::Space)),
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change_time_speed::<1>.run_if(input_just_pressed(KeyCode::Up)),
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change_time_speed::<-1>.run_if(input_just_pressed(KeyCode::Down)),
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(update_virtual_time_info_text, update_real_time_info_text)
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// update the texts on a timer to make them more readable
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// `on_timer` run condition uses `Virtual` time meaning it's scaled
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// and would result in the UI updating at different intervals based
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// on `Time<Virtual>::relative_speed` and `Time<Virtual>::is_paused()`
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.run_if(on_real_timer(Duration::from_millis(250))),
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),
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)
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.run();
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}
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/// `Real` time related marker
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#[derive(Component)]
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struct RealTime;
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/// `Virtual` time related marker
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#[derive(Component)]
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struct VirtualTime;
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/// Setup the example
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fn setup(mut commands: Commands, asset_server: Res<AssetServer>, mut time: ResMut<Time<Virtual>>) {
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// start with double `Virtual` time resulting in one of the sprites moving at twice the speed
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// of the other sprite which moves based on `Real` (unscaled) time
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time.set_relative_speed(2.);
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commands.spawn(Camera2dBundle::default());
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let virtual_color = Color::GOLD;
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let sprite_scale = Vec2::splat(0.5).extend(1.);
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let texture_handle = asset_server.load("branding/icon.png");
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// the sprite moving based on real time
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commands.spawn((
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SpriteBundle {
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texture: texture_handle.clone(),
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transform: Transform::from_scale(sprite_scale),
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..default()
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},
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RealTime,
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));
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// the sprite moving based on virtual time
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commands.spawn((
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SpriteBundle {
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texture: texture_handle,
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sprite: Sprite {
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color: virtual_color,
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..default()
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},
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transform: Transform {
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scale: sprite_scale,
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translation: Vec3::new(0., -160., 0.),
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..default()
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},
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..default()
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},
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VirtualTime,
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));
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// info UI
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let font_size = 40.;
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commands
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.spawn(NodeBundle {
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style: Style {
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display: Display::Flex,
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justify_content: JustifyContent::SpaceBetween,
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width: Val::Percent(100.),
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position_type: PositionType::Absolute,
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top: Val::Px(0.),
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padding: UiRect::all(Val::Px(20.0)),
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..default()
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},
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..default()
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})
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.with_children(|builder| {
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// real time info
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builder.spawn((
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TextBundle::from_section(
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"",
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TextStyle {
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font_size,
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..default()
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},
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),
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RealTime,
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));
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// keybindings
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builder.spawn(
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TextBundle::from_section(
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"CONTROLS\nUn/Pause: Space\nSpeed+: Up\nSpeed-: Down",
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TextStyle {
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font_size,
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color: Color::rgb(0.85, 0.85, 0.85),
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..default()
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},
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)
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.with_text_alignment(TextAlignment::Center),
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);
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// virtual time info
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builder.spawn((
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TextBundle::from_section(
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"",
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TextStyle {
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font_size,
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color: virtual_color,
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..default()
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},
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)
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.with_text_alignment(TextAlignment::Right),
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VirtualTime,
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));
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});
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}
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/// Move sprites using `Real` (unscaled) time
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fn move_real_time_sprites(
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mut sprite_query: Query<&mut Transform, (With<Sprite>, With<RealTime>)>,
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// `Real` time which is not scaled or paused
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time: Res<Time<Real>>,
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) {
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for mut transform in sprite_query.iter_mut() {
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// move roughly half the screen in a `Real` second
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// when the time is scaled the speed is going to change
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// and the sprite will stay still the the time is paused
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transform.translation.x = get_sprite_translation_x(time.elapsed_seconds());
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}
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}
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/// Move sprites using `Virtual` (scaled) time
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fn move_virtual_time_sprites(
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mut sprite_query: Query<&mut Transform, (With<Sprite>, With<VirtualTime>)>,
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// the default `Time` is either `Time<Virtual>` in regular systems
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// or `Time<Fixed>` in fixed timestep systems so `Time::delta()`,
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// `Time::elapsed()` will return the appropriate values either way
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time: Res<Time>,
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) {
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for mut transform in sprite_query.iter_mut() {
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// move roughly half the screen in a `Virtual` second
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// when time is scaled using `Time<Virtual>::set_relative_speed` it's going
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// to move at a different pace and the sprite will stay still when time is
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// `Time<Virtual>::is_paused()`
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transform.translation.x = get_sprite_translation_x(time.elapsed_seconds());
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}
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}
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fn get_sprite_translation_x(elapsed: f32) -> f32 {
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elapsed.sin() * 500.
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}
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/// Update the speed of `Time<Virtual>.` by `DELTA`
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fn change_time_speed<const DELTA: i8>(mut time: ResMut<Time<Virtual>>) {
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let time_speed = (time.relative_speed() + DELTA as f32)
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.round()
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.clamp(0.25, 5.);
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// set the speed of the virtual time to speed it up or slow it down
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time.set_relative_speed(time_speed);
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}
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/// pause or resume `Relative` time
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fn toggle_pause(mut time: ResMut<Time<Virtual>>) {
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if time.is_paused() {
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time.unpause();
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} else {
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time.pause();
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}
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}
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/// Update the `Real` time info text
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fn update_real_time_info_text(time: Res<Time<Real>>, mut query: Query<&mut Text, With<RealTime>>) {
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for mut text in &mut query {
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text.sections[0].value = format!(
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"REAL TIME\nElapsed: {:.1}\nDelta: {:.5}\n",
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time.elapsed_seconds(),
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time.delta_seconds(),
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);
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}
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}
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/// Update the `Virtual` time info text
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fn update_virtual_time_info_text(
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time: Res<Time<Virtual>>,
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mut query: Query<&mut Text, With<VirtualTime>>,
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) {
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for mut text in &mut query {
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text.sections[0].value = format!(
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"VIRTUAL TIME\nElapsed: {:.1}\nDelta: {:.5}\nSpeed: {:.2}",
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time.elapsed_seconds(),
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time.delta_seconds(),
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time.relative_speed()
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);
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}
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}
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