bevy/examples/camera/2d_top_down_camera.rs

150 lines
4.2 KiB
Rust
Raw Normal View History

//! This example showcases a 2D top-down camera with smooth player tracking.
//!
//! ## Controls
//!
//! | Key Binding | Action |
//! |:---------------------|:--------------|
//! | `Z`(azerty), `W`(US) | Move forward |
//! | `S` | Move backward |
//! | `Q`(azerty), `A`(US) | Move left |
//! | `D` | Move right |
use bevy::core_pipeline::bloom::BloomSettings;
use bevy::math::vec3;
use bevy::prelude::*;
use bevy::sprite::{MaterialMesh2dBundle, Mesh2dHandle};
/// Player movement speed factor.
const PLAYER_SPEED: f32 = 100.;
/// Camera lerp factor.
const CAM_LERP_FACTOR: f32 = 2.;
#[derive(Component)]
struct Player;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, (setup_scene, setup_instructions, setup_camera))
.add_systems(Update, (move_player, update_camera).chain())
.run();
}
fn setup_scene(
mut commands: Commands,
mut meshes: ResMut<Assets<Mesh>>,
mut materials: ResMut<Assets<ColorMaterial>>,
) {
// World where we move the player
commands.spawn(MaterialMesh2dBundle {
mesh: Mesh2dHandle(meshes.add(Rectangle::new(1000., 700.))),
material: materials.add(Color::srgb(0.2, 0.2, 0.3)),
..default()
});
// Player
commands.spawn((
Player,
MaterialMesh2dBundle {
mesh: meshes.add(Circle::new(25.)).into(),
material: materials.add(Color::srgb(6.25, 9.4, 9.1)), // RGB values exceed 1 to achieve a bright color for the bloom effect
transform: Transform {
translation: vec3(0., 0., 2.),
..default()
},
..default()
},
));
}
fn setup_instructions(mut commands: Commands) {
commands.spawn(
TextBundle::from_section(
"Move the light with ZQSD or WASD.\nThe camera will smoothly track the light.",
TextStyle::default(),
)
.with_style(Style {
position_type: PositionType::Absolute,
bottom: Val::Px(12.0),
left: Val::Px(12.0),
..default()
}),
);
}
fn setup_camera(mut commands: Commands) {
commands.spawn((
Camera2dBundle {
camera: Camera {
hdr: true, // HDR is required for the bloom effect
..default()
},
..default()
},
BloomSettings::NATURAL,
));
}
/// Update the camera position by tracking the player.
fn update_camera(
mut camera: Query<&mut Transform, (With<Camera2d>, Without<Player>)>,
player: Query<&Transform, (With<Player>, Without<Camera2d>)>,
time: Res<Time>,
) {
let Ok(mut camera) = camera.get_single_mut() else {
return;
};
let Ok(player) = player.get_single() else {
return;
};
let Vec3 { x, y, .. } = player.translation;
let direction = Vec3::new(x, y, camera.translation.z);
// Applies a smooth effect to camera movement using interpolation between
// the camera position and the player position on the x and y axes.
// Here we use the in-game time, to get the elapsed time (in seconds)
// since the previous update. This avoids jittery movement when tracking
// the player.
camera.translation = camera
.translation
.lerp(direction, time.delta_seconds() * CAM_LERP_FACTOR);
}
/// Update the player position with keyboard inputs.
fn move_player(
mut player: Query<&mut Transform, With<Player>>,
time: Res<Time>,
kb_input: Res<ButtonInput<KeyCode>>,
) {
let Ok(mut player) = player.get_single_mut() else {
return;
};
let mut direction = Vec2::ZERO;
if kb_input.pressed(KeyCode::KeyW) {
direction.y += 1.;
}
if kb_input.pressed(KeyCode::KeyS) {
direction.y -= 1.;
}
if kb_input.pressed(KeyCode::KeyA) {
direction.x -= 1.;
}
if kb_input.pressed(KeyCode::KeyD) {
direction.x += 1.;
}
// Progressively update the player's position over time. Normalize the
// direction vector to prevent it from exceeding a magnitude of 1 when
// moving diagonally.
let move_delta = direction.normalize_or_zero() * PLAYER_SPEED * time.delta_seconds();
player.translation += move_delta.extend(0.);
}