Bevy Animation Agent Skill

Bevy animation playback

When to use

Load this when an entity should play an AnimationClip. Blend graphs belong on bevy-animation-graph. 2D sprite specifics belong on bevy-2d-animation.

ECS shape

• Components: AnimationPlayer controls playback. AnimatedBy links a target entity to the player entity. AnimationTargetId selects which curves apply.
• Assets: AnimationClip holds VariableCurve entries.
• Systems: advance_animations advances time. animate_targets writes the curves. AnimationPlugin adds animation support.
• Events: AnimationEvent can be triggered from a clip. Check the animation docs for observer wiring beyond the trait name.

Playback pieces

| Need | Bevy idiom |

| --- | --- |

| Who advances time | AnimationPlayer on an entity |

| Clip asset | AnimationClip inside an AnimationGraph node |

| Which bone or field | AnimationTargetId plus AnimatedBy |

| Repeat | ActiveAnimation::repeat, which sets RepeatAnimation::Forever |

Examples

[dependencies]
bevy = "0.20"

AnimationPlayer::play takes an AnimationNodeIndex from an AnimationGraph, not a clip handle. AnimationGraph::from_clip builds that one-node graph. AnimatedBy points the target at the player entity. AnimationTargetId::from_name selects the curves for that name.

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

#[derive(Resource)]
struct WalkNode(AnimationNodeIndex);

fn setup_walk(
    mut commands: Commands,
    mut clips: ResMut<Assets<AnimationClip>>,
    mut graphs: ResMut<Assets<AnimationGraph>>,
) {
    let clip = clips.add(AnimationClip::default());
    let (graph, index) = AnimationGraph::from_clip(clip);
    let player = commands
        .spawn((
            AnimationPlayer::default(),
            AnimationGraphHandle(graphs.add(graph)),
        ))
        .id();
    commands.spawn((
        AnimatedBy(player),
        AnimationTargetId::from_name(&Name::new("Hips")),
        Transform::default(),
    ));
    commands.insert_resource(WalkNode(index));
}

fn play_loop(mut players: Query<&mut AnimationPlayer>, walk: Res<WalkNode>) {
    for mut player in &mut players {
        player.play(walk.0).repeat();
    }
}

Pause, resume, and seek act on every active clip on that player.

fn pause_players(mut players: Query<&mut AnimationPlayer>) {
    for mut player in &mut players {
        player.pause_all();
    }
}

fn resume_and_seek(mut players: Query<&mut AnimationPlayer>) {
    for mut player in &mut players {
        player.resume_all().seek_all_by(0.25);
    }
}

Stop one node, or ask whether it is still active, without touching the other clips on the same player.

fn stop_walk(mut players: Query<&mut AnimationPlayer>, walk: Res<WalkNode>) {
    for mut player in &mut players {
        if player.is_playing_animation(walk.0) {
            player.stop(walk.0);
        }
    }
}

#[derive(Resource)]
struct WalkNode(AnimationNodeIndex);

Scale every active clip on the player. glTF files load as AnimationClip assets; this player plays the graph node that holds that clip.

fn slow_motion(mut players: Query<&mut AnimationPlayer>) {
    for mut player in &mut players {
        player.adjust_speeds(0.5);
    }
}

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 plain struct stored outside the world |

| 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.

• Do not pass an AnimationClip handle to AnimationPlayer::play. WHY: play takes an AnimationNodeIndex from the graph built with AnimationGraph::from_clip.
• 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.
• Animation examples - Player, graph, and glTF clip samples.
• 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.

Complements

• bevy-animation-graph - Blend instead of a single clip.
• bevy-2d-animation - Sprite targets.
• bevy-asset-scenes - Load clip assets.

Downstream / consumers

• bevy-animation-graph - Consumes clips.

Master

• bevy-master - Bevy router.