17e504812b
# Objective clean up example get_single method, make code clean; ## Solution - replace `Query` with `Single` Query - remove `get_single` or `get_single_mut` condition block
124 lines
3.7 KiB
Rust
124 lines
3.7 KiB
Rust
//! This example showcases a 2D top-down camera with smooth player tracking.
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//!
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//! ## Controls
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//!
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//! | Key Binding | Action |
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//! |:---------------------|:--------------|
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//! | `W` | Move up |
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//! | `S` | Move down |
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//! | `A` | Move left |
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//! | `D` | Move right |
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use bevy::{core_pipeline::bloom::Bloom, prelude::*};
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/// Player movement speed factor.
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const PLAYER_SPEED: f32 = 100.;
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/// How quickly should the camera snap to the desired location.
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const CAMERA_DECAY_RATE: f32 = 2.;
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#[derive(Component)]
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struct Player;
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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_scene, setup_instructions, setup_camera))
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.add_systems(Update, (move_player, update_camera).chain())
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.run();
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}
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fn setup_scene(
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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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) {
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// World where we move the player
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commands.spawn((
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Mesh2d(meshes.add(Rectangle::new(1000., 700.))),
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MeshMaterial2d(materials.add(Color::srgb(0.2, 0.2, 0.3))),
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));
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// Player
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commands.spawn((
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Player,
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Mesh2d(meshes.add(Circle::new(25.))),
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MeshMaterial2d(materials.add(Color::srgb(6.25, 9.4, 9.1))), // RGB values exceed 1 to achieve a bright color for the bloom effect
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Transform::from_xyz(0., 0., 2.),
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));
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}
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fn setup_instructions(mut commands: Commands) {
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commands.spawn((
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Text::new("Move the light with WASD.\nThe camera will smoothly track the light."),
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Node {
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position_type: PositionType::Absolute,
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bottom: Val::Px(12.0),
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left: Val::Px(12.0),
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..default()
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},
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));
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}
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fn setup_camera(mut commands: Commands) {
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commands.spawn((
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Camera2d,
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Camera {
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hdr: true, // HDR is required for the bloom effect
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..default()
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},
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Bloom::NATURAL,
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));
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}
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/// Update the camera position by tracking the player.
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fn update_camera(
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mut camera: Single<&mut Transform, (With<Camera2d>, Without<Player>)>,
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player: Single<&Transform, (With<Player>, Without<Camera2d>)>,
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time: Res<Time>,
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) {
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let Vec3 { x, y, .. } = player.translation;
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let direction = Vec3::new(x, y, camera.translation.z);
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// Applies a smooth effect to camera movement using stable interpolation
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// between the camera position and the player position on the x and y axes.
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camera
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.translation
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.smooth_nudge(&direction, CAMERA_DECAY_RATE, time.delta_secs());
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}
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/// Update the player position with keyboard inputs.
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/// Note that the approach used here is for demonstration purposes only,
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/// as the point of this example is to showcase the camera tracking feature.
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///
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/// A more robust solution for player movement can be found in `examples/movement/physics_in_fixed_timestep.rs`.
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fn move_player(
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mut player: Single<&mut Transform, With<Player>>,
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time: Res<Time>,
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kb_input: Res<ButtonInput<KeyCode>>,
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) {
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let mut direction = Vec2::ZERO;
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if kb_input.pressed(KeyCode::KeyW) {
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direction.y += 1.;
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}
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if kb_input.pressed(KeyCode::KeyS) {
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direction.y -= 1.;
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}
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if kb_input.pressed(KeyCode::KeyA) {
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direction.x -= 1.;
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}
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if kb_input.pressed(KeyCode::KeyD) {
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direction.x += 1.;
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}
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// Progressively update the player's position over time. Normalize the
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// direction vector to prevent it from exceeding a magnitude of 1 when
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// moving diagonally.
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let move_delta = direction.normalize_or_zero() * PLAYER_SPEED * time.delta_secs();
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player.translation += move_delta.extend(0.);
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}
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