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# Objective Closes #15564 ## Solution Adds a screen shake example. --------- Co-authored-by: Alice Cecile <alice.i.cecile@gmail.com>
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//! This example showcases a 2D screen shake using concept in this video: `<https://www.youtube.com/watch?v=tu-Qe66AvtY>` | ||
//! | ||
//! ## Controls | ||
//! | ||
//! | Key Binding | Action | | ||
//! |:-------------|:---------------------| | ||
//! | Space | Trigger screen shake | | ||
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use bevy::{prelude::*, render::camera::SubCameraView, sprite::MeshMaterial2d}; | ||
use rand::{Rng, SeedableRng}; | ||
use rand_chacha::ChaCha8Rng; | ||
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const CAMERA_DECAY_RATE: f32 = 0.9; // Adjust this for smoother or snappier decay | ||
const TRAUMA_DECAY_SPEED: f32 = 0.5; // How fast trauma decays | ||
const TRAUMA_INCREMENT: f32 = 1.0; // Increment of trauma per frame when holding space | ||
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// screen_shake parameters, maximum addition by frame not actual maximum overall values | ||
const MAX_ANGLE: f32 = 0.5; | ||
const MAX_OFFSET: f32 = 500.0; | ||
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#[derive(Component)] | ||
struct Player; | ||
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fn main() { | ||
App::new() | ||
.add_plugins(DefaultPlugins) | ||
.add_systems(Startup, (setup_scene, setup_instructions, setup_camera)) | ||
.add_systems(Update, (screen_shake, trigger_shake_on_space)) | ||
.run(); | ||
} | ||
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fn setup_scene( | ||
mut commands: Commands, | ||
mut meshes: ResMut<Assets<Mesh>>, | ||
mut materials: ResMut<Assets<ColorMaterial>>, | ||
) { | ||
// World where we move the player | ||
commands.spawn(( | ||
Mesh2d(meshes.add(Rectangle::new(1000., 700.))), | ||
MeshMaterial2d(materials.add(Color::srgb(0.2, 0.2, 0.3))), | ||
)); | ||
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// Player | ||
commands.spawn(( | ||
Player, | ||
Mesh2d(meshes.add(Rectangle::new(50.0, 100.0))), // Rectangle size (width, height) | ||
MeshMaterial2d(materials.add(Color::srgb(0.25, 0.94, 0.91))), // RGB values must be in range 0.0 to 1.0 | ||
Transform::from_xyz(0., 0., 2.), | ||
)); | ||
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commands.spawn(( | ||
Mesh2d(meshes.add(Rectangle::new(50.0, 50.0))), // Rectangle size (width, height) | ||
MeshMaterial2d(materials.add(Color::srgb(0.85, 0.0, 0.2))), // RGB values must be in range 0.0 to 1.0 | ||
Transform::from_xyz(-450.0, 200.0, 2.), | ||
)); | ||
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commands.spawn(( | ||
Mesh2d(meshes.add(Rectangle::new(70.0, 50.0))), // Rectangle size (width, height) | ||
MeshMaterial2d(materials.add(Color::srgb(0.5, 0.8, 0.2))), // RGB values must be in range 0.0 to 1.0 | ||
Transform::from_xyz(450.0, -150.0, 2.), | ||
)); | ||
commands.init_resource::<ScreenShake>(); | ||
} | ||
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fn setup_instructions(mut commands: Commands) { | ||
commands.spawn( | ||
TextBundle::from_section("Hold space to trigger a screen shake", TextStyle::default()) | ||
.with_style(Style { | ||
position_type: PositionType::Absolute, | ||
bottom: Val::Px(12.0), | ||
left: Val::Px(12.0), | ||
..default() | ||
}), | ||
); | ||
} | ||
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fn setup_camera(mut commands: Commands) { | ||
commands.spawn(( | ||
Camera2d, | ||
Camera { | ||
sub_camera_view: Some(SubCameraView { | ||
full_size: UVec2::new(1000, 700), | ||
offset: Vec2::new(0.0, 0.0), | ||
size: UVec2::new(1000, 700), | ||
}), | ||
order: 1, | ||
..default() | ||
}, | ||
)); | ||
} | ||
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#[derive(Resource, Clone)] | ||
struct ScreenShake { | ||
max_angle: f32, | ||
max_offset: f32, | ||
trauma: f32, | ||
latest_position: Option<Vec2>, | ||
} | ||
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impl Default for ScreenShake { | ||
fn default() -> Self { | ||
Self { | ||
max_angle: 0.0, | ||
max_offset: 0.0, | ||
trauma: 0.0, | ||
latest_position: Some(Vec2::default()), | ||
} | ||
} | ||
} | ||
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impl ScreenShake { | ||
fn start_shake(&mut self, max_angle: f32, max_offset: f32, trauma: f32, final_position: Vec2) { | ||
self.max_angle = max_angle; | ||
self.max_offset = max_offset; | ||
self.trauma = trauma.clamp(0.0, 1.0); | ||
self.latest_position = Some(final_position); | ||
} | ||
} | ||
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fn trigger_shake_on_space( | ||
time: Res<Time>, | ||
keyboard_input: Res<ButtonInput<KeyCode>>, | ||
mut screen_shake: ResMut<ScreenShake>, | ||
) { | ||
if keyboard_input.pressed(KeyCode::Space) { | ||
let screen_shake_clone = screen_shake.clone(); | ||
screen_shake.start_shake( | ||
MAX_ANGLE, | ||
MAX_OFFSET, | ||
screen_shake_clone.trauma + TRAUMA_INCREMENT * time.delta_seconds(), | ||
Vec2 { x: 0.0, y: 0.0 }, | ||
); // final_position should be your current player position | ||
} | ||
} | ||
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fn screen_shake( | ||
time: Res<Time>, | ||
mut screen_shake: ResMut<ScreenShake>, | ||
mut query: Query<(&mut Camera, &mut Transform)>, | ||
) { | ||
let mut rng = ChaCha8Rng::from_entropy(); | ||
let shake = screen_shake.trauma * screen_shake.trauma; | ||
let angle = (screen_shake.max_angle * shake).to_radians() * rng.gen_range(-1.0..1.0); | ||
let offset_x = screen_shake.max_offset * shake * rng.gen_range(-1.0..1.0); | ||
let offset_y = screen_shake.max_offset * shake * rng.gen_range(-1.0..1.0); | ||
eprintln!("{} {}", offset_x, offset_y); | ||
if shake > 0.0 { | ||
for (mut camera, mut transform) in query.iter_mut() { | ||
// Position | ||
let sub_view = camera.sub_camera_view.as_mut().unwrap(); | ||
let target = sub_view.offset | ||
+ Vec2 { | ||
x: offset_x, | ||
y: offset_y, | ||
}; | ||
sub_view | ||
.offset | ||
.smooth_nudge(&target, CAMERA_DECAY_RATE, time.delta_seconds()); | ||
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// Rotation | ||
let rotation = Quat::from_rotation_z(angle); | ||
transform.rotation = transform | ||
.rotation | ||
.interpolate_stable(&(transform.rotation.mul_quat(rotation)), CAMERA_DECAY_RATE); | ||
} | ||
} else { | ||
// return camera to the latest position of player (it's fixed in this example case) | ||
if let Ok((mut camera, mut transform)) = query.get_single_mut() { | ||
let sub_view = camera.sub_camera_view.as_mut().unwrap(); | ||
let target = screen_shake.latest_position.unwrap(); | ||
sub_view | ||
.offset | ||
.smooth_nudge(&target, 1.0, time.delta_seconds()); | ||
transform.rotation = transform.rotation.interpolate_stable(&Quat::IDENTITY, 0.1); | ||
} | ||
} | ||
// Decay the trauma over time | ||
screen_shake.trauma -= TRAUMA_DECAY_SPEED * time.delta_seconds(); | ||
screen_shake.trauma = screen_shake.trauma.clamp(0.0, 1.0); | ||
} |