bevy/examples/3d/update_gltf_scene.rs
Carter Anderson dcc03724a5 Base Sets (#7466)
# 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
2023-02-06 03:10:08 +00:00

65 lines
2 KiB
Rust

//! Update a scene from a glTF file, either by spawning the scene as a child of another entity,
//! or by accessing the entities of the scene.
use bevy::prelude::*;
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_startup_system(setup)
.add_system(move_scene_entities)
.run();
}
#[derive(Component)]
struct MovedScene;
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(PointLightBundle {
transform: Transform::from_xyz(4.0, 5.0, 4.0),
..default()
});
commands.spawn(Camera3dBundle {
transform: Transform::from_xyz(1.05, 0.9, 1.5)
.looking_at(Vec3::new(0.0, 0.3, 0.0), Vec3::Y),
..default()
});
// Spawn the scene as a child of this entity at the given transform
commands.spawn(SceneBundle {
transform: Transform::from_xyz(0.0, 0.0, -1.0),
scene: asset_server.load("models/FlightHelmet/FlightHelmet.gltf#Scene0"),
..default()
});
// Spawn a second scene, and add a tag component to be able to target it later
commands.spawn((
SceneBundle {
scene: asset_server.load("models/FlightHelmet/FlightHelmet.gltf#Scene0"),
..default()
},
MovedScene,
));
}
// This system will move all entities that are descendants of MovedScene (which will be all entities spawned in the scene)
fn move_scene_entities(
time: Res<Time>,
moved_scene: Query<Entity, With<MovedScene>>,
children: Query<&Children>,
mut transforms: Query<&mut Transform>,
) {
for moved_scene_entity in &moved_scene {
let mut offset = 0.;
for entity in children.iter_descendants(moved_scene_entity) {
if let Ok(mut transform) = transforms.get_mut(entity) {
transform.translation = Vec3::new(
offset * time.elapsed_seconds().sin() / 20.,
0.,
time.elapsed_seconds().cos() / 20.,
);
offset += 1.0;
}
}
}
}