bevy/examples/ecs/hierarchy.rs
Joona Aalto 25bfa80e60
Migrate cameras to required components (#15641)
# Objective

Yet another PR for migrating stuff to required components. This time,
cameras!

## Solution

As per the [selected
proposal](https://hackmd.io/tsYID4CGRiWxzsgawzxG_g#Combined-Proposal-1-Selected),
deprecate `Camera2dBundle` and `Camera3dBundle` in favor of `Camera2d`
and `Camera3d`.

Adding a `Camera` without `Camera2d` or `Camera3d` now logs a warning,
as suggested by Cart [on
Discord](https://discord.com/channels/691052431525675048/1264881140007702558/1291506402832945273).
I would personally like cameras to work a bit differently and be split
into a few more components, to avoid some footguns and confusing
semantics, but that is more controversial, and shouldn't block this core
migration.

## Testing

I ran a few 2D and 3D examples, and tried cameras with and without
render graphs.

---

## Migration Guide

`Camera2dBundle` and `Camera3dBundle` have been deprecated in favor of
`Camera2d` and `Camera3d`. Inserting them will now also insert the other
components required by them automatically.
2024-10-05 01:59:52 +00:00

92 lines
3.1 KiB
Rust

//! Creates a hierarchy of parents and children entities.
use std::f32::consts::*;
use bevy::{color::palettes::css::*, prelude::*};
fn main() {
App::new()
.add_plugins(DefaultPlugins)
.add_systems(Startup, setup)
.add_systems(Update, rotate)
.run();
}
fn setup(mut commands: Commands, asset_server: Res<AssetServer>) {
commands.spawn(Camera2d);
let texture = asset_server.load("branding/icon.png");
// Spawn a root entity with no parent
let parent = commands
.spawn(SpriteBundle {
transform: Transform::from_scale(Vec3::splat(0.75)),
texture: texture.clone(),
..default()
})
// With that entity as a parent, run a lambda that spawns its children
.with_children(|parent| {
// parent is a ChildBuilder, which has a similar API to Commands
parent.spawn(SpriteBundle {
transform: Transform::from_xyz(250.0, 0.0, 0.0).with_scale(Vec3::splat(0.75)),
texture: texture.clone(),
sprite: Sprite {
color: BLUE.into(),
..default()
},
..default()
});
})
// Store parent entity for next sections
.id();
// Another way is to use the add_child function to add children after the parent
// entity has already been spawned.
let child = commands
.spawn(SpriteBundle {
transform: Transform::from_xyz(0.0, 250.0, 0.0).with_scale(Vec3::splat(0.75)),
texture,
sprite: Sprite {
color: LIME.into(),
..default()
},
..default()
})
.id();
// Add child to the parent.
commands.entity(parent).add_child(child);
}
// A simple system to rotate the root entity, and rotate all its children separately
fn rotate(
mut commands: Commands,
time: Res<Time>,
mut parents_query: Query<(Entity, &Children), With<Sprite>>,
mut transform_query: Query<&mut Transform, With<Sprite>>,
) {
for (parent, children) in &mut parents_query {
if let Ok(mut transform) = transform_query.get_mut(parent) {
transform.rotate_z(-PI / 2. * time.delta_seconds());
}
// To iterate through the entities children, just treat the Children component as a Vec
// Alternatively, you could query entities that have a Parent component
for child in children {
if let Ok(mut transform) = transform_query.get_mut(*child) {
transform.rotate_z(PI * time.delta_seconds());
}
}
// To demonstrate removing children, we'll remove a child after a couple of seconds.
if time.elapsed_seconds() >= 2.0 && children.len() == 2 {
let child = children.last().unwrap();
commands.entity(*child).despawn_recursive();
}
if time.elapsed_seconds() >= 4.0 {
// This will remove the entity from its parent's list of children, as well as despawn
// any children the entity has.
commands.entity(parent).despawn_recursive();
}
}
}