use std::f32::consts::PI;  use bevy::{     light::CascadeShadowConfigBuilder, post_process::effect_stack::ChromaticAberration, prelude::*,     render::view::Hdr, };  /// The number of units per frame to add to or subtract from intensity when the /// arrow keys are held. const CHROMATIC_ABERRATION_INTENSITY_ADJUSTMENT_SPEED: f32 = 0.002;  /// The maximum supported chromatic aberration intensity level. const MAX_CHROMATIC_ABERRATION_INTENSITY: f32 = 0.4;  /// The settings that the user can control. #[derive(Resource)] struct AppSettings {     /// The intensity of the chromatic aberration effect.     chromatic_aberration_intensity: f32, }  /// The entry point. fn main() {     App::new()         .init_resource::<AppSettings>()         .add_plugins(DefaultPlugins.set(WindowPlugin {             primary_window: Some(Window {                 title: "Bevy Chromatic Aberration Example".into(),                 ..default()             }),             ..default()         }))         .add_systems(Startup, setup)         .add_systems(Update, handle_keyboard_input)         .add_systems(             Update,             (update_chromatic_aberration_settings, update_help_text)                 .run_if(resource_changed::<AppSettings>)                 .after(handle_keyboard_input),         )         .run(); }  /// Creates the example scene and spawns the UI. fn setup(mut commands: Commands, asset_server: Res<AssetServer>, app_settings: Res<AppSettings>) {     // Spawn the camera.     spawn_camera(&mut commands, &asset_server);      // Create the scene.     spawn_scene(&mut commands, &asset_server);      // Spawn the help text.     spawn_text(&mut commands, &app_settings); }  /// Spawns the camera, including the [`ChromaticAberration`] component. fn spawn_camera(commands: &mut Commands, asset_server: &AssetServer) {     commands.spawn((         Camera3d::default(),         Hdr,         Transform::from_xyz(0.7, 0.7, 1.0).looking_at(Vec3::new(0.0, 0.3, 0.0), Vec3::Y),         DistanceFog {             color: Color::srgb_u8(43, 44, 47),             falloff: FogFalloff::Linear {                 start: 1.0,                 end: 8.0,             },             ..default()         },         EnvironmentMapLight {             diffuse_map: asset_server.load("environment_maps/pisa_diffuse_rgb9e5_zstd.ktx2"),             specular_map: asset_server.load("environment_maps/pisa_specular_rgb9e5_zstd.ktx2"),             intensity: 2000.0,             ..default()         },         // Include the `ChromaticAberration` component.         ChromaticAberration::default(),     )); }  /// Spawns the scene. /// /// This is just the tonemapping test scene, chosen for the fact that it uses a /// variety of colors. fn spawn_scene(commands: &mut Commands, asset_server: &AssetServer) {     // Spawn the main scene.     commands.spawn(SceneRoot(asset_server.load(         GltfAssetLabel::Scene(0).from_asset("models/TonemappingTest/TonemappingTest.gltf"),     )));      // Spawn the flight helmet.     commands.spawn((         SceneRoot(             asset_server                 .load(GltfAssetLabel::Scene(0).from_asset("models/FlightHelmet/FlightHelmet.gltf")),         ),         Transform::from_xyz(0.5, 0.0, -0.5).with_rotation(Quat::from_rotation_y(-0.15 * PI)),     ));      // Spawn the light.     commands.spawn((         DirectionalLight {             illuminance: 15000.0,             shadows_enabled: true,             ..default()         },         Transform::from_rotation(Quat::from_euler(EulerRot::ZYX, 0.0, PI * -0.15, PI * -0.15)),         CascadeShadowConfigBuilder {             maximum_distance: 3.0,             first_cascade_far_bound: 0.9,             ..default()         }         .build(),     )); }  /// Spawns the help text at the bottom of the screen. fn spawn_text(commands: &mut Commands, app_settings: &AppSettings) {     commands.spawn((         create_help_text(app_settings),         Node {             position_type: PositionType::Absolute,             bottom: px(12),             left: px(12),             ..default()         },     )); }  impl Default for AppSettings {     fn default() -> Self {         Self {             chromatic_aberration_intensity: ChromaticAberration::default().intensity,         }     } }  /// Creates help text at the bottom of the screen. fn create_help_text(app_settings: &AppSettings) -> Text {     format!(         "Chromatic aberration intensity: {:.2} (Press Left or Right to change)",         app_settings.chromatic_aberration_intensity     )     .into() }  /// Handles requests from the user to change the chromatic aberration intensity. fn handle_keyboard_input(mut app_settings: ResMut<AppSettings>, input: Res<ButtonInput<KeyCode>>) {     let mut delta = 0.0;     if input.pressed(KeyCode::ArrowLeft) {         delta -= CHROMATIC_ABERRATION_INTENSITY_ADJUSTMENT_SPEED;     } else if input.pressed(KeyCode::ArrowRight) {         delta += CHROMATIC_ABERRATION_INTENSITY_ADJUSTMENT_SPEED;     }      // If no arrow key was pressed, just bail out.     if delta == 0.0 {         return;     }      app_settings.chromatic_aberration_intensity = (app_settings.chromatic_aberration_intensity         + delta)         .clamp(0.0, MAX_CHROMATIC_ABERRATION_INTENSITY); }  /// Updates the [`ChromaticAberration`] settings per the [`AppSettings`]. fn update_chromatic_aberration_settings(     mut chromatic_aberration: Query<&mut ChromaticAberration>,     app_settings: Res<AppSettings>, ) {     let intensity = app_settings.chromatic_aberration_intensity;      // Pick a reasonable maximum sample size for the intensity to avoid an     // artifact whereby the individual samples appear instead of producing     // smooth streaks of color.     //     // Don't take this formula too seriously; it hasn't been heavily tuned.     let max_samples = ((intensity - 0.02) / (0.20 - 0.02) * 56.0 + 8.0)         .clamp(8.0, 64.0)         .round() as u32;      for mut chromatic_aberration in &mut chromatic_aberration {         chromatic_aberration.intensity = intensity;         chromatic_aberration.max_samples = max_samples;     } }  /// Updates the help text at the bottom of the screen to reflect the current /// [`AppSettings`]. fn update_help_text(mut text: Query<&mut Text>, app_settings: Res<AppSettings>) {     for mut text in text.iter_mut() {         *text = create_help_text(&app_settings);     } }