mirror of
https://github.com/bevyengine/bevy
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7482a0d26d
Fixes #15834 ## Migration Guide The APIs of `Time`, `Timer` and `Stopwatch` have been cleaned up for consistency with each other and the standard library's `Duration` type. The following methods have been renamed: - `Stowatch::paused` -> `Stopwatch::is_paused` - `Time::elapsed_seconds` -> `Time::elasped_secs` (including `_f64` and `_wrapped` variants)
153 lines
4.7 KiB
Rust
153 lines
4.7 KiB
Rust
//! This example illustrates how to load and play different soundtracks,
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//! transitioning between them as the game state changes.
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use bevy::prelude::*;
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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(Update, (cycle_game_state, fade_in, fade_out))
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.add_systems(Update, change_track)
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.run();
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}
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// This resource simulates game states
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#[derive(Resource, Default)]
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enum GameState {
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#[default]
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Peaceful,
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Battle,
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}
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// This timer simulates game state changes
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#[derive(Resource)]
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struct GameStateTimer(Timer);
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// This resource will hold the track list for your soundtrack
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#[derive(Resource)]
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struct SoundtrackPlayer {
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track_list: Vec<Handle<AudioSource>>,
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}
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impl SoundtrackPlayer {
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fn new(track_list: Vec<Handle<AudioSource>>) -> Self {
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Self { track_list }
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}
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}
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// This component will be attached to an entity to fade the audio in
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#[derive(Component)]
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struct FadeIn;
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// This component will be attached to an entity to fade the audio out
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#[derive(Component)]
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struct FadeOut;
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fn setup(asset_server: Res<AssetServer>, mut commands: Commands) {
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// Instantiate the game state resources
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commands.insert_resource(GameState::default());
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commands.insert_resource(GameStateTimer(Timer::from_seconds(
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10.0,
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TimerMode::Repeating,
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)));
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// Create the track list
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let track_1 = asset_server.load::<AudioSource>("sounds/Mysterious acoustic guitar.ogg");
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let track_2 = asset_server.load::<AudioSource>("sounds/Epic orchestra music.ogg");
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let track_list = vec![track_1, track_2];
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commands.insert_resource(SoundtrackPlayer::new(track_list));
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}
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// Every time the GameState resource changes, this system is run to trigger the song change.
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fn change_track(
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mut commands: Commands,
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soundtrack_player: Res<SoundtrackPlayer>,
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soundtrack: Query<Entity, With<AudioSink>>,
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game_state: Res<GameState>,
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) {
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if game_state.is_changed() {
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// Fade out all currently running tracks
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for track in soundtrack.iter() {
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commands.entity(track).insert(FadeOut);
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}
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// Spawn a new `AudioPlayer` with the appropriate soundtrack based on
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// the game state.
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//
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// Volume is set to start at zero and is then increased by the fade_in system.
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match game_state.as_ref() {
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GameState::Peaceful => {
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commands.spawn((
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AudioPlayer(soundtrack_player.track_list.first().unwrap().clone()),
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PlaybackSettings {
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mode: bevy::audio::PlaybackMode::Loop,
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volume: bevy::audio::Volume::ZERO,
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..default()
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},
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FadeIn,
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));
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}
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GameState::Battle => {
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commands.spawn((
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AudioPlayer(soundtrack_player.track_list.get(1).unwrap().clone()),
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PlaybackSettings {
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mode: bevy::audio::PlaybackMode::Loop,
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volume: bevy::audio::Volume::ZERO,
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..default()
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},
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FadeIn,
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));
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}
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}
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}
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}
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// Fade effect duration
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const FADE_TIME: f32 = 2.0;
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// Fades in the audio of entities that has the FadeIn component. Removes the FadeIn component once
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// full volume is reached.
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fn fade_in(
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mut commands: Commands,
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mut audio_sink: Query<(&mut AudioSink, Entity), With<FadeIn>>,
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time: Res<Time>,
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) {
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for (audio, entity) in audio_sink.iter_mut() {
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audio.set_volume(audio.volume() + time.delta_secs() / FADE_TIME);
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if audio.volume() >= 1.0 {
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audio.set_volume(1.0);
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commands.entity(entity).remove::<FadeIn>();
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}
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}
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}
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// Fades out the audio of entities that has the FadeOut component. Despawns the entities once audio
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// volume reaches zero.
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fn fade_out(
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mut commands: Commands,
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mut audio_sink: Query<(&mut AudioSink, Entity), With<FadeOut>>,
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time: Res<Time>,
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) {
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for (audio, entity) in audio_sink.iter_mut() {
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audio.set_volume(audio.volume() - time.delta_secs() / FADE_TIME);
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if audio.volume() <= 0.0 {
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commands.entity(entity).despawn_recursive();
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}
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}
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}
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// Every time the timer ends, switches between the "Peaceful" and "Battle" state.
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fn cycle_game_state(
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mut timer: ResMut<GameStateTimer>,
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mut game_state: ResMut<GameState>,
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time: Res<Time>,
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) {
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timer.0.tick(time.delta());
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if timer.0.just_finished() {
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match game_state.as_ref() {
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GameState::Battle => *game_state = GameState::Peaceful,
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GameState::Peaceful => *game_state = GameState::Battle,
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}
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}
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}
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