d3d9cab30c
# Objective
- Improve the code quality of the breakout example
- As a newcomer to `bevy` I was pointed to the breakout example after
the "Getting Started" tutorial
- I'm making this PR because it had a few wrong comments + some
inconsistency in used patterns
## Solution
- Remove references to `wall` in all the collision code as it also
handles bricks and the paddle
- Use the newtype pattern with `bevy::prelude::Deref` for resources
- It was already used for `Velocity` before this PR
- `Scoreboard` is a resource only containing `score`, so it's simpler as
a newtype `Score` resource
- `CollisionSound` is already a newtype, so might as well unify the
access pattern for it
- Added docstrings for `WallLocation::position` and `WallLocation::size`
to explain what they represent
460 lines
15 KiB
Rust
460 lines
15 KiB
Rust
//! A simplified implementation of the classic game "Breakout".
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use bevy::{
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math::bounding::{Aabb2d, BoundingCircle, BoundingVolume, IntersectsVolume},
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prelude::*,
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sprite::MaterialMesh2dBundle,
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};
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mod stepping;
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// These constants are defined in `Transform` units.
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// Using the default 2D camera they correspond 1:1 with screen pixels.
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const PADDLE_SIZE: Vec2 = Vec2::new(120.0, 20.0);
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const GAP_BETWEEN_PADDLE_AND_FLOOR: f32 = 60.0;
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const PADDLE_SPEED: f32 = 500.0;
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// How close can the paddle get to the wall
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const PADDLE_PADDING: f32 = 10.0;
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// We set the z-value of the ball to 1 so it renders on top in the case of overlapping sprites.
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const BALL_STARTING_POSITION: Vec3 = Vec3::new(0.0, -50.0, 1.0);
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const BALL_DIAMETER: f32 = 30.;
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const BALL_SPEED: f32 = 400.0;
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const INITIAL_BALL_DIRECTION: Vec2 = Vec2::new(0.5, -0.5);
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const WALL_THICKNESS: f32 = 10.0;
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// x coordinates
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const LEFT_WALL: f32 = -450.;
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const RIGHT_WALL: f32 = 450.;
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// y coordinates
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const BOTTOM_WALL: f32 = -300.;
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const TOP_WALL: f32 = 300.;
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const BRICK_SIZE: Vec2 = Vec2::new(100., 30.);
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// These values are exact
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const GAP_BETWEEN_PADDLE_AND_BRICKS: f32 = 270.0;
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const GAP_BETWEEN_BRICKS: f32 = 5.0;
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// These values are lower bounds, as the number of bricks is computed
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const GAP_BETWEEN_BRICKS_AND_CEILING: f32 = 20.0;
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const GAP_BETWEEN_BRICKS_AND_SIDES: f32 = 20.0;
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const SCOREBOARD_FONT_SIZE: f32 = 40.0;
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const SCOREBOARD_TEXT_PADDING: Val = Val::Px(5.0);
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const BACKGROUND_COLOR: Color = Color::srgb(0.9, 0.9, 0.9);
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const PADDLE_COLOR: Color = Color::srgb(0.3, 0.3, 0.7);
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const BALL_COLOR: Color = Color::srgb(1.0, 0.5, 0.5);
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const BRICK_COLOR: Color = Color::srgb(0.5, 0.5, 1.0);
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const WALL_COLOR: Color = Color::srgb(0.8, 0.8, 0.8);
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const TEXT_COLOR: Color = Color::srgb(0.5, 0.5, 1.0);
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const SCORE_COLOR: Color = Color::srgb(1.0, 0.5, 0.5);
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_plugins(
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stepping::SteppingPlugin::default()
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.add_schedule(Update)
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.add_schedule(FixedUpdate)
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.at(Val::Percent(35.0), Val::Percent(50.0)),
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)
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.insert_resource(Score(0))
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.insert_resource(ClearColor(BACKGROUND_COLOR))
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.add_event::<CollisionEvent>()
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.add_systems(Startup, setup)
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// Add our gameplay simulation systems to the fixed timestep schedule
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// which runs at 64 Hz by default
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.add_systems(
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FixedUpdate,
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(
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apply_velocity,
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move_paddle,
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check_for_collisions,
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play_collision_sound,
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)
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// `chain`ing systems together runs them in order
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.chain(),
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)
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.add_systems(Update, (update_scoreboard, bevy::window::close_on_esc))
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.run();
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}
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#[derive(Component)]
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struct Paddle;
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#[derive(Component)]
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struct Ball;
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#[derive(Component, Deref, DerefMut)]
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struct Velocity(Vec2);
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#[derive(Component)]
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struct Collider;
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#[derive(Event, Default)]
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struct CollisionEvent;
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#[derive(Component)]
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struct Brick;
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#[derive(Resource, Deref)]
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struct CollisionSound(Handle<AudioSource>);
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// This bundle is a collection of the components that define a "wall" in our game
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#[derive(Bundle)]
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struct WallBundle {
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// You can nest bundles inside of other bundles like this
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// Allowing you to compose their functionality
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sprite_bundle: SpriteBundle,
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collider: Collider,
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}
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/// Which side of the arena is this wall located on?
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enum WallLocation {
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Left,
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Right,
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Bottom,
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Top,
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}
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impl WallLocation {
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/// Location of the *center* of the wall, used in `transform.translation()`
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fn position(&self) -> Vec2 {
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match self {
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WallLocation::Left => Vec2::new(LEFT_WALL, 0.),
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WallLocation::Right => Vec2::new(RIGHT_WALL, 0.),
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WallLocation::Bottom => Vec2::new(0., BOTTOM_WALL),
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WallLocation::Top => Vec2::new(0., TOP_WALL),
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}
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}
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/// (x, y) dimensions of the wall, used in `transform.scale()`
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fn size(&self) -> Vec2 {
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let arena_height = TOP_WALL - BOTTOM_WALL;
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let arena_width = RIGHT_WALL - LEFT_WALL;
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// Make sure we haven't messed up our constants
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assert!(arena_height > 0.0);
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assert!(arena_width > 0.0);
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match self {
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WallLocation::Left | WallLocation::Right => {
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Vec2::new(WALL_THICKNESS, arena_height + WALL_THICKNESS)
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}
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WallLocation::Bottom | WallLocation::Top => {
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Vec2::new(arena_width + WALL_THICKNESS, WALL_THICKNESS)
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}
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}
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}
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}
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impl WallBundle {
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// This "builder method" allows us to reuse logic across our wall entities,
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// making our code easier to read and less prone to bugs when we change the logic
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fn new(location: WallLocation) -> WallBundle {
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WallBundle {
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sprite_bundle: SpriteBundle {
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transform: Transform {
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// We need to convert our Vec2 into a Vec3, by giving it a z-coordinate
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// This is used to determine the order of our sprites
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translation: location.position().extend(0.0),
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// The z-scale of 2D objects must always be 1.0,
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// or their ordering will be affected in surprising ways.
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// See https://github.com/bevyengine/bevy/issues/4149
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scale: location.size().extend(1.0),
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..default()
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},
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sprite: Sprite {
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color: WALL_COLOR,
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..default()
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},
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..default()
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},
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collider: Collider,
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}
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}
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}
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// This resource tracks the game's score
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#[derive(Resource, Deref, DerefMut)]
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struct Score(usize);
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#[derive(Component)]
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struct ScoreboardUi;
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// Add the game's entities to our world
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fn setup(
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mut commands: Commands,
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mut meshes: ResMut<Assets<Mesh>>,
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mut materials: ResMut<Assets<ColorMaterial>>,
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asset_server: Res<AssetServer>,
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) {
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// Camera
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commands.spawn(Camera2dBundle::default());
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// Sound
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let ball_collision_sound = asset_server.load("sounds/breakout_collision.ogg");
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commands.insert_resource(CollisionSound(ball_collision_sound));
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// Paddle
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let paddle_y = BOTTOM_WALL + GAP_BETWEEN_PADDLE_AND_FLOOR;
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commands.spawn((
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SpriteBundle {
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transform: Transform {
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translation: Vec3::new(0.0, paddle_y, 0.0),
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scale: PADDLE_SIZE.extend(1.0),
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..default()
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},
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sprite: Sprite {
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color: PADDLE_COLOR,
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..default()
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},
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..default()
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},
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Paddle,
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Collider,
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));
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// Ball
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commands.spawn((
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MaterialMesh2dBundle {
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mesh: meshes.add(Circle::default()).into(),
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material: materials.add(BALL_COLOR),
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transform: Transform::from_translation(BALL_STARTING_POSITION)
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.with_scale(Vec2::splat(BALL_DIAMETER).extend(1.)),
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..default()
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},
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Ball,
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Velocity(INITIAL_BALL_DIRECTION.normalize() * BALL_SPEED),
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));
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// Scoreboard
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commands.spawn((
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ScoreboardUi,
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TextBundle::from_sections([
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TextSection::new(
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"Score: ",
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TextStyle {
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font_size: SCOREBOARD_FONT_SIZE,
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color: TEXT_COLOR,
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..default()
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},
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),
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TextSection::from_style(TextStyle {
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font_size: SCOREBOARD_FONT_SIZE,
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color: SCORE_COLOR,
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..default()
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}),
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])
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.with_style(Style {
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position_type: PositionType::Absolute,
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top: SCOREBOARD_TEXT_PADDING,
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left: SCOREBOARD_TEXT_PADDING,
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..default()
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}),
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));
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// Walls
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commands.spawn(WallBundle::new(WallLocation::Left));
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commands.spawn(WallBundle::new(WallLocation::Right));
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commands.spawn(WallBundle::new(WallLocation::Bottom));
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commands.spawn(WallBundle::new(WallLocation::Top));
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// Bricks
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let total_width_of_bricks = (RIGHT_WALL - LEFT_WALL) - 2. * GAP_BETWEEN_BRICKS_AND_SIDES;
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let bottom_edge_of_bricks = paddle_y + GAP_BETWEEN_PADDLE_AND_BRICKS;
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let total_height_of_bricks = TOP_WALL - bottom_edge_of_bricks - GAP_BETWEEN_BRICKS_AND_CEILING;
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assert!(total_width_of_bricks > 0.0);
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assert!(total_height_of_bricks > 0.0);
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// Given the space available, compute how many rows and columns of bricks we can fit
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let n_columns = (total_width_of_bricks / (BRICK_SIZE.x + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_rows = (total_height_of_bricks / (BRICK_SIZE.y + GAP_BETWEEN_BRICKS)).floor() as usize;
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let n_vertical_gaps = n_columns - 1;
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// Because we need to round the number of columns,
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// the space on the top and sides of the bricks only captures a lower bound, not an exact value
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let center_of_bricks = (LEFT_WALL + RIGHT_WALL) / 2.0;
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let left_edge_of_bricks = center_of_bricks
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// Space taken up by the bricks
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- (n_columns as f32 / 2.0 * BRICK_SIZE.x)
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// Space taken up by the gaps
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- n_vertical_gaps as f32 / 2.0 * GAP_BETWEEN_BRICKS;
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// In Bevy, the `translation` of an entity describes the center point,
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// not its bottom-left corner
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let offset_x = left_edge_of_bricks + BRICK_SIZE.x / 2.;
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let offset_y = bottom_edge_of_bricks + BRICK_SIZE.y / 2.;
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for row in 0..n_rows {
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for column in 0..n_columns {
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let brick_position = Vec2::new(
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offset_x + column as f32 * (BRICK_SIZE.x + GAP_BETWEEN_BRICKS),
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offset_y + row as f32 * (BRICK_SIZE.y + GAP_BETWEEN_BRICKS),
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);
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// brick
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commands.spawn((
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SpriteBundle {
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sprite: Sprite {
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color: BRICK_COLOR,
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..default()
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},
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transform: Transform {
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translation: brick_position.extend(0.0),
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scale: Vec3::new(BRICK_SIZE.x, BRICK_SIZE.y, 1.0),
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..default()
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},
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..default()
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},
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Brick,
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Collider,
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));
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}
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}
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}
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fn move_paddle(
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keyboard_input: Res<ButtonInput<KeyCode>>,
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mut query: Query<&mut Transform, With<Paddle>>,
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time: Res<Time>,
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) {
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let mut paddle_transform = query.single_mut();
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let mut direction = 0.0;
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if keyboard_input.pressed(KeyCode::ArrowLeft) {
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direction -= 1.0;
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}
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if keyboard_input.pressed(KeyCode::ArrowRight) {
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direction += 1.0;
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}
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// Calculate the new horizontal paddle position based on player input
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let new_paddle_position =
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paddle_transform.translation.x + direction * PADDLE_SPEED * time.delta_seconds();
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// Update the paddle position,
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// making sure it doesn't cause the paddle to leave the arena
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let left_bound = LEFT_WALL + WALL_THICKNESS / 2.0 + PADDLE_SIZE.x / 2.0 + PADDLE_PADDING;
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let right_bound = RIGHT_WALL - WALL_THICKNESS / 2.0 - PADDLE_SIZE.x / 2.0 - PADDLE_PADDING;
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paddle_transform.translation.x = new_paddle_position.clamp(left_bound, right_bound);
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}
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fn apply_velocity(mut query: Query<(&mut Transform, &Velocity)>, time: Res<Time>) {
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for (mut transform, velocity) in &mut query {
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transform.translation.x += velocity.x * time.delta_seconds();
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transform.translation.y += velocity.y * time.delta_seconds();
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}
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}
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fn update_scoreboard(score: Res<Score>, mut query: Query<&mut Text, With<ScoreboardUi>>) {
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let mut text = query.single_mut();
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text.sections[1].value = score.to_string();
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}
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fn check_for_collisions(
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mut commands: Commands,
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mut score: ResMut<Score>,
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mut ball_query: Query<(&mut Velocity, &Transform), With<Ball>>,
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collider_query: Query<(Entity, &Transform, Option<&Brick>), With<Collider>>,
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mut collision_events: EventWriter<CollisionEvent>,
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) {
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let (mut ball_velocity, ball_transform) = ball_query.single_mut();
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for (collider_entity, collider_transform, maybe_brick) in &collider_query {
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let collision = ball_collision(
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BoundingCircle::new(ball_transform.translation.truncate(), BALL_DIAMETER / 2.),
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Aabb2d::new(
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collider_transform.translation.truncate(),
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collider_transform.scale.truncate() / 2.,
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),
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);
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if let Some(collision) = collision {
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// Sends a collision event so that other systems can react to the collision
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collision_events.send_default();
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// Bricks should be despawned and increment the scoreboard on collision
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if maybe_brick.is_some() {
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commands.entity(collider_entity).despawn();
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**score += 1;
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}
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// Reflect the ball's velocity when it collides
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let mut reflect_x = false;
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let mut reflect_y = false;
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// Reflect only if the velocity is in the opposite direction of the collision
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// This prevents the ball from getting stuck inside the bar
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match collision {
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Collision::Left => reflect_x = ball_velocity.x > 0.0,
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Collision::Right => reflect_x = ball_velocity.x < 0.0,
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Collision::Top => reflect_y = ball_velocity.y < 0.0,
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Collision::Bottom => reflect_y = ball_velocity.y > 0.0,
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}
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// Reflect velocity on the x-axis if we hit something on the x-axis
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if reflect_x {
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ball_velocity.x = -ball_velocity.x;
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}
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// Reflect velocity on the y-axis if we hit something on the y-axis
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if reflect_y {
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ball_velocity.y = -ball_velocity.y;
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}
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}
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}
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}
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fn play_collision_sound(
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mut commands: Commands,
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mut collision_events: EventReader<CollisionEvent>,
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sound: Res<CollisionSound>,
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) {
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// Play a sound once per frame if a collision occurred.
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if !collision_events.is_empty() {
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// This prevents events staying active on the next frame.
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collision_events.clear();
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commands.spawn(AudioBundle {
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source: sound.clone(),
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// auto-despawn the entity when playback finishes
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settings: PlaybackSettings::DESPAWN,
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});
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}
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}
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#[derive(Debug, PartialEq, Eq, Copy, Clone)]
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enum Collision {
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Left,
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Right,
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Top,
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Bottom,
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}
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// Returns `Some` if `ball` collides with `bounding_box`.
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// The returned `Collision` is the side of `bounding_box` that `ball` hit.
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fn ball_collision(ball: BoundingCircle, bounding_box: Aabb2d) -> Option<Collision> {
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if !ball.intersects(&bounding_box) {
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return None;
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}
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let closest = bounding_box.closest_point(ball.center());
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let offset = ball.center() - closest;
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let side = if offset.x.abs() > offset.y.abs() {
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if offset.x < 0. {
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Collision::Left
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} else {
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Collision::Right
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}
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} else if offset.y > 0. {
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Collision::Top
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} else {
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Collision::Bottom
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};
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Some(side)
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}
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