dcc03724a5
# Objective NOTE: This depends on #7267 and should not be merged until #7267 is merged. If you are reviewing this before that is merged, I highly recommend viewing the Base Sets commit instead of trying to find my changes amongst those from #7267. "Default sets" as described by the [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) have some [unfortunate consequences](https://github.com/bevyengine/bevy/discussions/7365). ## Solution This adds "base sets" as a variant of `SystemSet`: A set is a "base set" if `SystemSet::is_base` returns `true`. Typically this will be opted-in to using the `SystemSet` derive: ```rust #[derive(SystemSet, Clone, Hash, Debug, PartialEq, Eq)] #[system_set(base)] enum MyBaseSet { A, B, } ``` **Base sets are exclusive**: a system can belong to at most one "base set". Adding a system to more than one will result in an error. When possible we fail immediately during system-config-time with a nice file + line number. For the more nested graph-ey cases, this will fail at the final schedule build. **Base sets cannot belong to other sets**: this is where the word "base" comes from Systems and Sets can only be added to base sets using `in_base_set`. Calling `in_set` with a base set will fail. As will calling `in_base_set` with a normal set. ```rust app.add_system(foo.in_base_set(MyBaseSet::A)) // X must be a normal set ... base sets cannot be added to base sets .configure_set(X.in_base_set(MyBaseSet::A)) ``` Base sets can still be configured like normal sets: ```rust app.add_system(MyBaseSet::B.after(MyBaseSet::Ap)) ``` The primary use case for base sets is enabling a "default base set": ```rust schedule.set_default_base_set(CoreSet::Update) // this will belong to CoreSet::Update by default .add_system(foo) // this will override the default base set with PostUpdate .add_system(bar.in_base_set(CoreSet::PostUpdate)) ``` This allows us to build apis that work by default in the standard Bevy style. This is a rough analog to the "default stage" model, but it use the new "stageless sets" model instead, with all of the ordering flexibility (including exclusive systems) that it provides. --- ## Changelog - Added "base sets" and ported CoreSet to use them. ## Migration Guide TODO
68 lines
2.0 KiB
Rust
68 lines
2.0 KiB
Rust
//! Illustrates how to create parent-child relationships between entities and how parent transforms
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//! are propagated to their descendants.
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use bevy::prelude::*;
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fn main() {
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App::new()
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.add_plugins(DefaultPlugins)
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.add_startup_system(setup)
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.add_system(rotator_system)
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.run();
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}
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/// this component indicates what entities should rotate
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#[derive(Component)]
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struct Rotator;
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/// rotates the parent, which will result in the child also rotating
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fn rotator_system(time: Res<Time>, mut query: Query<&mut Transform, With<Rotator>>) {
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for mut transform in &mut query {
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transform.rotate_x(3.0 * time.delta_seconds());
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}
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}
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/// set up a simple scene with a "parent" cube and a "child" cube
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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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let cube_handle = meshes.add(Mesh::from(shape::Cube { size: 2.0 }));
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let cube_material_handle = materials.add(StandardMaterial {
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base_color: Color::rgb(0.8, 0.7, 0.6),
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..default()
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});
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// parent cube
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commands
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.spawn((
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PbrBundle {
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mesh: cube_handle.clone(),
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material: cube_material_handle.clone(),
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transform: Transform::from_xyz(0.0, 0.0, 1.0),
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..default()
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},
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Rotator,
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))
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.with_children(|parent| {
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// child cube
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parent.spawn(PbrBundle {
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mesh: cube_handle,
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material: cube_material_handle,
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transform: Transform::from_xyz(0.0, 0.0, 3.0),
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..default()
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});
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});
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// light
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commands.spawn(PointLightBundle {
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transform: Transform::from_xyz(4.0, 5.0, -4.0),
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..default()
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});
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// camera
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commands.spawn(Camera3dBundle {
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transform: Transform::from_xyz(5.0, 10.0, 10.0).looking_at(Vec3::ZERO, Vec3::Y),
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..default()
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});
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}
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