Bevy 2D animation

When to use

Load this when a 2D actor needs clip playback on a sprite entity. Pair with bevy-animation for the player and clip types. Pair with bevy-animation-graph when clips must blend.

ECS shape

• Components: Sprite (bevy::sprite) on the visible entity. AnimationPlayer and AnimationTargetId / AnimatedBy (bevy::animation) link a clip to that entity.
• Resources: clip assets are AnimationClip handles, not a global player.
• Systems: advance_animations and animate_targets are the engine systems named on the animation page. Gameplay code should not reimplement them.
• Schedule: those systems are engine-owned. Gameplay that reacts to a finished clip chains after them.

Playback choices

Need	Bevy idiom
Frame cells	Sprite with texture_atlas: Some(TextureAtlas { .. }), or an AnimationClip curve.
Named cutout limb	AnimationTargetId::from_name / from_names selects which entity a curve writes.
Loop	ActiveAnimation::repeat sets RepeatAnimation::Forever.

Scope

• Frame sheets use Sprite::from_atlas_image and TextureAtlas. Clip curves use animated_field! plus AnimatableCurve.
• A cutout limb is an entity with AnimationTargetId and AnimatedBy pointing at the entity that owns AnimationPlayer.

Examples

Atlas frame on a sprite. TextureAtlas.index is the cell.

fn spawn_sheet(
    mut commands: Commands,
    assets: Res<AssetServer>,
    mut layouts: ResMut<Assets<TextureAtlasLayout>>,
) {
    let layout = TextureAtlasLayout::from_grid(UVec2::splat(32), 4, 1, None, None);
    let layout = layouts.add(layout);
    let image = assets.load("actor.png");
    commands.spawn((
        Sprite::from_atlas_image(image, TextureAtlas { layout, index: 0 }),
        FrameClock {
            timer: Timer::from_seconds(0.12, TimerMode::Repeating),
            frames: 4,
        },
    ));
}

#[derive(Component)]
struct FrameClock {
    timer: Timer,
    frames: usize,
}

fn tick_frames(time: Res<Time>, mut sprites: Query<(&mut Sprite, &mut FrameClock)>) {
    for (mut sprite, mut clock) in &mut sprites {
        clock.timer.tick(time.delta());
        if clock.timer.just_finished() {
            if let Some(atlas) = sprite.texture_atlas.as_mut() {
                atlas.index = (atlas.index + 1) % clock.frames;
            }
        }
    }
}

Clip playback. The player stores an AnimationNodeIndex from the graph, not a raw clip handle.

use bevy::animation::animated_field;
use bevy::animation::{AnimatedBy, AnimationTargetId};

#[derive(Component)]
struct IdleNode(AnimationNodeIndex);

fn spawn_clip(
    mut commands: Commands,
    mut clips: ResMut<Assets<AnimationClip>>,
    mut graphs: ResMut<Assets<AnimationGraph>>,
) {
    let name = Name::new("actor");
    let target = AnimationTargetId::from_name(&name);
    let samples = UnevenSampleAutoCurve::new([
        (0.0, Vec3::ZERO),
        (0.4, Vec3::new(8.0, 0.0, 0.0)),
    ])
    .expect("two samples");
    let mut clip = AnimationClip::default();
    clip.add_curve_to_target(
        target,
        AnimatableCurve::new(animated_field!(Transform::translation), samples),
    );
    let clip_handle = clips.add(clip);
    let (graph, indices) = AnimationGraph::from_clips([clip_handle]);
    let idle = indices[0];
    let graph_handle = graphs.add(graph);
    let player = commands
        .spawn((
            name,
            Sprite::from_color(Color::WHITE, Vec2::splat(32.0)),
            AnimationPlayer::default(),
            AnimationGraphHandle(graph_handle),
            target,
            IdleNode(idle),
        ))
        .id();
    commands.entity(player).insert(AnimatedBy(player));
}

fn play_idle(mut actors: Query<(&mut AnimationPlayer, &IdleNode)>) {
    for (mut player, idle) in &mut actors {
        player.play(idle.0).repeat();
    }
}

fn cutout_id(root: &Name, limb: &Name) -> AnimationTargetId {
    AnimationTargetId::from_names([root, limb].into_iter())
}

Facing and frame ticks both write Sprite, so they share one chain.

fn face_keys(keys: Res<ButtonInput<KeyCode>>, mut sprites: Query<&mut Sprite>) {
    let left = keys.pressed(KeyCode::KeyA);
    let right = keys.pressed(KeyCode::KeyD);
    if !left && !right {
        return;
    }
    for mut sprite in &mut sprites {
        sprite.flip_x = left;
    }
}

#[derive(Component)]
struct SheetClock {
    timer: Timer,
    frames: usize,
}

fn advance_sheet(time: Res<Time>, mut sprites: Query<(&mut Sprite, &mut SheetClock)>) {
    for (mut sprite, mut clock) in &mut sprites {
        clock.timer.tick(time.delta());
        if clock.timer.just_finished() {
            if let Some(atlas) = sprite.texture_atlas.as_mut() {
                atlas.index = (atlas.index + 1) % clock.frames;
            }
        }
    }
}

pub struct SpriteAnimPlugin;

impl Plugin for SpriteAnimPlugin {
    fn build(&self, app: &mut App) {
        app.add_systems(Update, (face_keys, advance_sheet).chain());
    }
}

Expert Knowledge Delta

Target: Bevy 0.20+.

Core ECS types: Component, Resource, Query, Commands, Startup, Update, Fixed / FixedMain (bevy::time), .chain(), Plugin, DefaultPlugins, MinimalPlugins. Messages and observers are an ownership slot. See bevy-events-messaging for their APIs. Systems run in parallel unless .chain() orders the ones that conflict.

Who owns state

Piece	Owner	Who may mutate	Schedule
Data on one entity	Component	One system via Query	Update or FixedMain
One value for the whole app	Resource	One system	Startup to insert, then the schedule that reads it
Spawn	Commands	The spawning system	Startup for the initial world; later schedules for runtime spawn
Order that must not race	.chain()	The chained systems only	Same schedule
Plugin boundary	Plugin	build registers systems and resources	Before the app runs

Borrow rule: two systems that both mutably query the same component must be ordered (.chain()) or split so only one writes. Unrelated systems stay parallel. That is the ECS page rule, not a guess at a system-set API.

Decision

If you need	Do this	Do not
Per-entity data	Component + Query	A value stored off the entity
App-wide config or clock	Resource	Copy the value onto every entity
Stable simulation step	FixedMain and the Fixed clock	Tie simulation to raw frame Update
Startup spawn	Commands in Startup	Spawn from a render system
Cross-system notice that is not shared state	Message or observer slot in bevy-events-messaging	A new event type invented in this file
An API outside the documented set	Check the official docs first	A made-up crate or API

Load references/ecs-ownership.md for the ownership table.

NEVER

• Do not pin /0.20.0/ in docs URLs. WHY: links stay on latest; the 0.20 target is stated once in prose.

• Do not mutably query the same component from two unordered systems. WHY: the schedule runs systems in parallel unless .chain() orders them.

• Do not invent a physics, navigation, networking, or XR crate here. WHY: this skill only names documented Bevy crates and modules.

• No sprite-frame type outside Sprite, TextureAtlas, and AnimationClip. WHY: those are the documented owners of a 2D frame and a sampled curve.

• No invented APIs or unnamed third-party crates as the chosen solver. WHY: Bevy code stays idiomatic ECS and uses only documented Bevy APIs.

Reference

The library pin on bevy-master stays 0.20.0. Permalinks stay unversioned.

Official Documentation

• Assets - Official asset catalog. No third-party crate was selected.
• Examples - Example tree on the latest branch.
• 2D examples - Sprite and atlas samples.
• Animation examples - AnimationPlayer, clips, and graphs.
• ECS - Component, systems, Query, Startup, Update, and .chain().
• Plugins - Plugin, DefaultPlugins, MinimalPlugins, and add_plugins.

Related Skills

Prerequisites

• bevy-master - Hub and schedules.
• bevy-ecs-composition - Components and systems.
• bevy-animation - AnimationPlayer and AnimationClip.

Complements

• bevy-animation-graph - Blend clips.

Downstream / consumers

• None yet.

Master

• bevy-master - Bevy router.