# M2 Animation Playback Controller

## Metadata

| Field | Value |
|---|---|
| Status | Implemented extraction |
| Target/work package | M03 / `M03-RND-M2-ANIMATION-PLAYBACK-001` |
| Owners | Per-instance AnimationPlayer/native animator playback mutation |
| Last verified | Worktree `work/sindo-main-codex/m03-m2-animation-playback`, 2026-07-18 |
| Profiles/capabilities | Imported GLB and native experimental animated M2 instances |

## Purpose

Apply deterministic playback to one already duplicated M2 instance: copy native
animator runtime fields, derive a stable phase, prepare/phase native animators,
select an imported animation and configure linear looping/playback/seek.

## Non-goals

- Duplicate, name, transform or attach instances/batch roots.
- Apply visibility, shadows or Editor ownership.
- Load/finalize/cache animated scenes or decide eligibility.
- Change animation priorities, phase formula or native animator implementation.

## Context and boundaries

```mermaid
flowchart LR
    Prototype[Animated prototype] --> Materializer[M2AnimatedInstanceMaterializer]
    Materializer -->|source and duplicate| Playback[M2AnimationPlaybackController]
    Finalizer[M2AnimatedSceneFinalizer player inventory] --> Playback
    Playback --> Native[M2NativeAnimator mutation]
    Playback --> Imported[AnimationPlayer mutation]
```

Allowed dependencies are supplied Nodes, Script identity, AnimationPlayer and
Animation resources. ResourceLoader, files, workers, caches, scheduler,
MultiMesh, SceneTree attachment and application layers are forbidden.

## Public API

| Symbol | Kind | Purpose | Thread/lifetime | Errors |
|---|---|---|---|---|
| `copy_native_animator_data(source_root, target_root, script)` | Command | Copy five runtime fields in depth-first pair order | Main thread; borrowed nodes | Null/script mismatch yields no pairs |
| `start_instance_playback(root, path, index, script, players, collect_diagnostics)` | Command/query | Start native/imported playback and optionally return native state | Main thread; one instance | Null/empty inventories no-op |
| `native_animators_in_subtree(root, script)` | Query | Exact-script depth-first inventory | Main thread; borrowed nodes | Null root/script returns empty |
| `phase_for_instance(path, index)` | Pure query | Stable phase in `[0, 1)` | Any thread; scalar | Historical hash behavior retained |
| `choose_default_animation(player, path)` | Pure engine query | Apply exact ordinary/fish/bird/fallback priority | Main thread; borrowed player | Null/no animations returns empty |

## Inputs and outputs

| Direction | Contract/data | Producer | Consumer | Ownership | Thread/lifetime |
|---|---|---|---|---|---|
| Input | Prototype and duplicate subtrees | M2 animated instance materializer | Native field copy | Borrowed Nodes | One duplicate |
| Input | Exact native animator Script | Loader composition | Native inventory | Borrowed Script | Call-local |
| Input | Relative path and instance index | Build batch adapter | Phase/selection | Copied values | One start |
| Input | AnimationPlayer inventory | Animated scene finalizer traversal | Imported playback | Borrowed players | One start |
| Output | Mutated native/imported playback | Controller | Rendered instance | Nodes retain state/resources | Instance lifetime |
| Output | Detached native diagnostic records | Controller | Loader log adapter | Caller-owned Dictionaries | Debug call |

Side effects are native field assignment, prepare/phase calls, animation loop
mutation, play and seek. The service retains no inputs.

## Data flow

```mermaid
flowchart TD
    Identity[Path and index] --> Phase[Stable hash phase]
    NativeInventory[Exact-script native inventory] --> Prepare[prepare runtime if available]
    Phase --> NativePhase[set native phase]
    Players[AnimationPlayers] --> Select[Choose path-specific default]
    Select --> Loop[Set every animation LOOP_LINEAR]
    Loop --> Play[Play selected name]
    Phase --> Seek[Seek positive-length selection]
    NativePhase --> Diagnostics{Debug requested?}
    Diagnostics -->|yes| Snapshot[Detached runtime state]
```

## Lifecycle/state

```mermaid
stateDiagram-v2
    [*] --> Unstarted
    Unstarted --> Prepared: copy native data and start
    Prepared --> Playing: native phase and/or AnimationPlayer play
    Playing --> Playing: repeated deterministic start
    Playing --> [*]: instance owner releases subtree
```

The controller itself is stateless; lifecycle labels describe borrowed instance state.

## Main sequence

```mermaid
sequenceDiagram
    participant M as M2AnimatedInstanceMaterializer
    participant F as M2AnimatedSceneFinalizer
    participant P as M2AnimationPlaybackController
    participant N as M2NativeAnimator
    participant A as AnimationPlayer
    M->>P: copy_native_animator_data(prototype, duplicate, script)
    M->>F: animation_players_in_subtree(duplicate)
    F-->>M: ordered players
    M->>P: start_instance_playback(path, index, players, debug)
    P->>N: prepare_runtime and set_phase
    P->>A: choose, loop, play and seek
    P-->>M: optional detached native diagnostics
    M-->>M: tag states with instance index
```

## Dependency diagram

```mermaid
flowchart TB
    Loader[StreamingWorldLoader] --> Materializer[M2AnimatedInstanceMaterializer]
    Materializer --> Playback[M2AnimationPlaybackController]
    Materializer --> Finalizer[M2AnimatedSceneFinalizer]
    Playback --> Engine[Node / Script / AnimationPlayer / Animation]
    Materializer --> Batch[SceneTree batch materialization]
    Loader --> NativeScript[M2NativeAnimator script]
    Playback -. no dependency .-> ResourceLoader
    Playback -. no dependency .-> Cache[M2PrototypeCacheState]
    Playback -. no dependency .-> Scheduler[RenderBudgetScheduler]
```

## Ownership, threading and resources

- Materializer owns prototype duplication, instance/batch roots and SceneTree attachment.
- Materializer uses finalizer traversal for borrowed AnimationPlayer references.
- Controller borrows Nodes/Script/players only for the synchronous call.
- Native arrays are assigned by reference exactly as before extraction.
- Diagnostic Dictionaries are deep-duplicated before return.
- Main thread performs all engine-object mutation; pure phase math is thread-safe.

## Errors, cancellation and recovery

| Failure | Detection | Behavior | Diagnostic | Recovery |
|---|---|---|---|---|
| Missing roots/script | Inventory guard | No native copy/start | Contract fixture | Correct composition |
| Fewer target animators | Pair-count minimum | Copy available pairs only | Native copy fixture | Rebuild import/prototype |
| No matching name | Ordered fallback | Substring, first name, then empty | Selection fixtures | Add compatible animation |
| Empty animation selection | Empty result | Skip loop/play/seek for that player | Selection fixture | Static/native path continues |
| Zero-length selected animation | Length guard | Play without seek | Playback contract | Imported timing remains engine-owned |
| Cancellation/shutdown | Outside service | No retained state | N/A | Loader owns subtree release |

## Configuration and capabilities

| Setting/capability | Default | Profile | Runtime mutable | Effect |
|---|---|---|---|---|
| Phase buckets | 1000 | All | No | Stable per path/index desynchronization |
| Loop mode | `LOOP_LINEAR` | All | No | Every available imported animation loops |
| Native diagnostics | `debug_streaming` | Debug | Yes | Samples state only when requested |

## Persistence, cache and migration

No state or format is serialized. GLB/native cache formats, prototype lifetime
and material versions are unchanged; no rebake is required.

## Diagnostics and observability

- Optional native states remain detached and contain existing prepared,
  processing, mesh, bone, surface and length fields.
- Loader retains `M2_NATIVE_ANIMATOR` log formatting and path normalization.
- Controller emits no logs or metrics.

## Verification

- `verify_m2_animation_playback_controller.gd` covers exact phase, ordinary/
  fish/bird priorities, substring/first fallback, loop/play/seek, native exact-
  script order, five-field copy, phase, detached diagnostics and boundaries.
- Finalizer/build/prototype/material/shutdown regressions protect adjacent behavior.
- Fidelity evidence is exact policy/mutation extraction; no private asset or
  original-client animation comparison is claimed.
- Performance budget: 20,000 phase-and-selection pairs under one second.

## Extension points

Server-driven animation state may later replace default selection through a
separate presentation contract; this fallback controller must remain available
for world doodads and compatibility fixtures.

## Capability status

| Capability | Status | Evidence | Gap/next step |
|---|---|---|---|
| Imported default selection/playback | Implemented extraction | Synthetic priority/play/seek verifier | Asset-backed animation-name corpus pending |
| Native data/phase startup | Implemented extraction | Exact-reference/native state verifier | Native visual fidelity remains experimental |
| Instance/batch materialization | Implemented extraction | Materializer contract verifier | Asset-backed traversal pending |

## Known gaps and risks

- Hash phase intentionally depends on existing Godot String hashing behavior.
- Default-name heuristics are not a complete WoW animation-state mapping.
- No proprietary traversal, animation timing comparison, p95/p99 or paired-client run exists.

## Source map

| Path | Responsibility |
|---|---|
| `src/render/m2/m2_animation_playback_controller.gd` | Phase, selection, native copy/start and imported playback |
| `src/render/m2/m2_animated_scene_finalizer.gd` | Accepted prototype/player inventory |
| `src/scenes/streaming/m2_native_animator.gd` | Experimental native deformation runtime |
| `src/render/m2/m2_animated_instance_materializer.gd` | Instance duplication/attachment and playback composition |
| `src/scenes/streaming/streaming_world_loader.gd` | Build adapter, diagnostic formatting and Editor ownership |
| `src/tools/verify_m2_animation_playback_controller.gd` | Policy/mutation/boundary/timing regression |

## Related decisions and references

- [`m2-animated-scene-finalizer.md`](m2-animated-scene-finalizer.md)
- [`m2-build-batch-planner.md`](m2-build-batch-planner.md)
- [`world-renderer.md`](world-renderer.md)
- [`../../RENDER.md`](../../RENDER.md)
- [`../../targets/roadmap/02-rendering-and-graphics.md`](../../targets/roadmap/02-rendering-and-graphics.md)
