gods-eye-view/docs/DIRECTOR.md

Director: reusable scene playback

Director is the scene playback system. Ordered shot execution, authored timing and playback clocks are separated from the scene editor and application rendering. This document also records the proposed next steps; the sharing format and interactions below are a design plan, not features already available.

Implemented boundary

src/director/playback.js, exported as gods-eye-view/director, provides:

• buildPlaybackQueue(scenes, startSceneId, { single }): ordered scenes/shots, retaining the existing round-robin behavior.
• playSceneQueue(queue, { token, adapter, previousScene, releaseOnFinish }): sequential execution, cancellation checks and scene release.

The runner imports no renderer, UI, storage, recipe or dataset. An adapter supplies these phases, in order: selectShot, applyVisual, applyLayers, travel, settle, hold, completeShot. Each receives { scene, shot, index, total, token }. It also supplies releaseScene(scene, token?) and optionally complete(). Callbacks may return promises. Each playback invocation requires its own adapter state and token; the caller owns camera arbitration and concurrent-run refusal.

The runner checks cancellation after each phase. Adapters must also pass the abort signal or liveness predicate into pending work: a check between phases cannot stop a camera flight or network request already in progress. Cleanup between scenes and on preview exit runs without an aborted token. A refused initial handoff starts no shot. Final cleanup runs on completion, Stop or failure; releaseOnFinish: false retains the final scene for ordinary playback. Exceptions propagate so the caller can restore its controls. Empty/already-cancelled queues acquire no resources. This low-level API expects normalized scene objects; untrusted file validation belongs at the import boundary.

src/scenes/playbackAdapter.js connects this runner to the existing SceneDirector. The latter still owns editor state, saved-project import/export, camera ownership and asynchronous load/seek arbitration. Pure seek calculations live in src/director/timeline.js; src/director/clock.js owns the run/load/shot tickers, hold deadlines, snapshots and clock subscriptions. Stop settles pending holds immediately, and revoked tick callbacks cannot affect a replacement clock. getPlaybackTimingState() exposes copied snapshots and an active-timer count for lifecycle diagnostics without exposing timer handles.

The director export also provides sceneTimingForShot, sceneSeekState, cameraAtProgress and createPlaybackClock. Timeline functions receive duration and hold resolvers; the clock receives timing, running-state and progress callbacks. They import no renderer, storage, recipe or dataset.

src/scenes/shotPresentation.js prepares layer/seek context and resolves holds and map preferences through a scene-pack registry. The scenes export provides createScenePackRegistry({ recipes, adapters }); pass the result as scenePacks in the SceneDirector constructor options. Trusted adapters can supply minimumHoldSec(states), resolveVisual(shot, visual, isMapStackAvailable) and cancelMotion(getLayerModule). Default composition registers the existing Nepal presentation rules. These are code-level composition hooks, not executable modules imported from scene files. Existing media-owner waits remain bounded.

All authored scenes, assets, IDs, source links, attribution and existing JSON projects are preserved. The Nepal sequence remains the contribution introduced by @manjunath22466 in #590. Its clips use source links/embeds; comparison images and river coordinates are bundled. See the event pack provenance.

Next changes, in order

1. Timeline and content separation — implemented. Pure duration/seek calculations, an owned clock and registered presentation rules preserve existing recipes and content. Tests cover direct load, forward/backward seek, replay, bounded media waits and cancellation at pending transitions.
2. Versioned scene document — implemented for existing camera-pose shots. Version 3 remains the write format. Bounded validation rejects malformed files before replacing current state; legacy migration preserves IDs, pack bindings and visual edits. Unreadable saved files are protected from fallback writes. Camera anchors, pack manifests and actions receive stable IDs with their respective later format extensions.
3. Camera directions. Define named geographic anchors and explicit move/hold segments: start and destination, duration, easing, heading, pitch, roll and stop duration. State coordinate units, altitude reference and terrain-relative behavior. Support the current camera-pose shots first; paths, look-at targets and pauses follow with deterministic seek behavior.
4. Data packs and placement. Define a pack manifest with format/version, source, attribution/license and optional integrity/size metadata. Distinguish where bytes live (relative files, a URL, or an eventual bundle) from where features appear (geographic bounds, anchors, transforms and elevation rules). Start with existing GeoJSON/image/media adapters. Resolve relative paths against an explicit document base; define CORS, caching, missing-asset and offline behavior. Fetch only through registered source adapters with bounded, cancellable loading. Scene files carry no credentials or executable modules.
5. Declarative interactions. Give pickable features stable IDs and connect clicks to a small action registry: show a text/source card, focus an anchor, seek a shot, or change an allowed layer state. Define selection feedback, keyboard equivalents and precedence with drawing/tracking controls. Validate target references and cancel pending actions on Stop, replacement or teardown. No JavaScript evaluation or arbitrary HTML in scene files. Branching must have explicit loop/transition limits and reproducible reset/seek semantics.
6. Sharing and authoring. Add validated preview/import/export, missing-pack diagnostics and an optional self-contained bundle. Preserve attribution with each pack; a share link does not change an asset's license. A future node graph could author this same document, but playback and the format will not require a graph editor.

Each step must preserve existing scene editing, keyboard playback, camera arbitration, layer cleanup, media timing and provider fallback. Acceptance includes portable runner tests, existing Director regressions and browser playback with Stop/seek/replay, plus tracking and voice checks. Use reproducible local fixtures for failures and cancellation, alongside live visual checks for actual content.