75 lines
2.2 KiB
Rust
75 lines
2.2 KiB
Rust
//! Illustrates how to move an object along an axis.
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use bevy::prelude::*;
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// Define a struct to keep some information about our entity.
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// Here it's an arbitrary movement speed, the spawn location, and a maximum distance from it.
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#[derive(Component)]
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struct Movable {
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spawn: Vec3,
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max_distance: f32,
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speed: f32,
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}
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// Implement a utility function for easier Movable struct creation.
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impl Movable {
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fn new(spawn: Vec3) -> Self {
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Movable {
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spawn,
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max_distance: 5.0,
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speed: 2.0,
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}
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}
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}
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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)
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.add_systems(Update, move_cube)
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.run();
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}
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// Startup system to setup the scene and spawn all relevant entities.
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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<StandardMaterial>>,
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) {
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// Add a cube to visualize translation.
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let entity_spawn = Vec3::ZERO;
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commands.spawn((
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PbrBundle {
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mesh: meshes.add(Mesh::from(shape::Cube { size: 1.0 })),
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material: materials.add(Color::WHITE.into()),
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transform: Transform::from_translation(entity_spawn),
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..default()
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},
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Movable::new(entity_spawn),
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));
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// Spawn a camera looking at the entities to show what's happening in this example.
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commands.spawn(Camera3dBundle {
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transform: Transform::from_xyz(0.0, 10.0, 20.0).looking_at(entity_spawn, Vec3::Y),
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..default()
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});
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// Add a light source for better 3d visibility.
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commands.spawn(PointLightBundle {
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transform: Transform::from_translation(Vec3::ONE * 3.0),
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..default()
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});
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}
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// This system will move all Movable entities with a Transform
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fn move_cube(mut cubes: Query<(&mut Transform, &mut Movable)>, timer: Res<Time>) {
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for (mut transform, mut cube) in &mut cubes {
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// Check if the entity moved too far from its spawn, if so invert the moving direction.
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if (cube.spawn - transform.translation).length() > cube.max_distance {
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cube.speed *= -1.0;
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}
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let direction = transform.local_x();
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transform.translation += direction * cube.speed * timer.delta_seconds();
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}
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}
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