docs/bevy/examples/3d/parenting.rs 1.7 K · 57 lines · raw · history

1 //! Illustrates how to create parent-child relationships between entities and how parent transforms
2 //! are propagated to their descendants.
3
4 use bevy::prelude::*;
5
6 fn main() {
7 App::new()
8 .add_plugins(DefaultPlugins)
9 .add_systems(Startup, setup)
10 .add_systems(Update, rotator_system)
11 .run();
12 }
13
14 /// this component indicates what entities should rotate
15 #[derive(Component)]
16 struct Rotator;
17
18 /// rotates the parent, which will result in the child also rotating
19 fn rotator_system(time: Res<Time>, mut query: Query<&mut Transform, With<Rotator>>) {
20 for mut transform in &mut query {
21 transform.rotate_x(3.0 * time.delta_secs());
22 }
23 }
24
25 /// set up a simple scene with a "parent" cube and a "child" cube
26 fn setup(
27 mut commands: Commands,
28 mut meshes: ResMut<Assets<Mesh>>,
29 mut materials: ResMut<Assets<StandardMaterial>>,
30 ) {
31 let cube_handle = meshes.add(Cuboid::new(2.0, 2.0, 2.0));
32 let cube_material_handle = materials.add(StandardMaterial {
33 base_color: Color::srgb(0.8, 0.7, 0.6),
34 ..default()
35 });
36
37 // parent cube
38 commands.spawn((
39 Mesh3d(cube_handle.clone()),
40 MeshMaterial3d(cube_material_handle.clone()),
41 Transform::from_xyz(0.0, 0.0, 1.0),
42 Rotator,
43 children![(
44 // child cube
45 Mesh3d(cube_handle),
46 MeshMaterial3d(cube_material_handle),
47 Transform::from_xyz(0.0, 0.0, 3.0),
48 )],
49 ));
50 // light
51 commands.spawn((PointLight::default(), Transform::from_xyz(4.0, 5.0, -4.0)));
52 // camera
53 commands.spawn((
54 Camera3d::default(),
55 Transform::from_xyz(5.0, 10.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
56 ));
57 }