72 lines
3.7 KiB
Markdown
72 lines
3.7 KiB
Markdown
# Atomic collision-generation activation (Slice 3B)
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## Retail anchor
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Retail hydrates a cell synchronously. `CObjCell::init_objects`
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(`0x0052B420`) visits objects associated with that cell and invokes
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`CPhysicsObj::recalc_cross_cells` (`0x00515A30`). The final position path also
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replaces shadows as one `SetPositionInternal` operation (`0x00515330`). Retail
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therefore never exposes a world where the new cell exists but the objects that
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overlap it still have their old cross-cell set.
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Acdream streams a landblock over several update frames. Literal per-cell
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mutation during those frames was not equivalent: the active `PhysicsDataCache`,
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`CellGraph`, `PhysicsEngine`, buildings, static shadows, and retained-object
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refloods changed at different cursors. Collision queries could observe a mixed
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generation, and correctness depended on a later optional landblock callback.
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## Ported adaptation
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The asynchronous unit is now one Runtime-owned collision generation:
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1. `BeginCollisionAdmission` issues the exact Runtime/landblock generation.
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2. `PrepareCollisionGeneration` clones the bounded resident spatial records
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into a private cache, graph, engine, and shadow registry. Global immutable
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GfxObj/Setup catalogs are not copied; the accepted build's exact closure is
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populated by the existing cursors.
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3. App and Headless publish terrain, EnvCells, topology, buildings, prepared
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collision assets, static owners, and retained dynamic-owner cell sets only
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into that private generation.
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4. Each dynamic owner refresh captures its exact `ShadowObjectRegistry`
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mutation version. Movement, state/payload change, spawn, suspension, or
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deletion changes that version.
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5. `CommitCollisionGeneration` validates the admission, exact affected-owner
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set, and all captured versions. If any owner is dirty, it returns the sorted
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dirty IDs without touching the active world; App advances those IDs through
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its existing work meter and retries.
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6. Once fresh, Runtime precomputes the replacement arrays and synchronously
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replaces the landblock's cache/graph/engine/building/static and dynamic
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shadow state on the same update thread. Only after the complete replacement
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does it emit `CollisionGenerationCommitted` and a ready acknowledgement.
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The stable borrowed `PhysicsEngine` and `PhysicsDataCache` object identities do
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not change. Presentation and no-window hosts use the same Runtime transaction.
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Network workers still enqueue immutable messages and cannot mutate collision or
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shadow state.
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## Failure and lifetime rules
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- A newer admission invalidates an older prepared generation.
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- Demotion, withdrawal, reset, and disposal invalidate the admission before
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changing the active generation.
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- Disposing a stale/cancelled prepared generation clears only its private
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engine/cache/shadows.
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- The prior complete generation remains queryable throughout preparation.
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- The commit notification is the future lost-cell-registry seam. Slice 3B does
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not implement `GotoLostCell` or change `SetPosition` recovery behavior.
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## Deterministic evidence
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The focused Runtime/App tests pin:
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- previous terrain/cells/buildings/statics remain visible until commit;
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- exactly one notification after a successful complete activation;
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- stale admission replacement has no active-world side effect;
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- movement during staging rejects, refreshes only the dirty owner, and then
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installs its latest cell set;
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- spawn and deletion during staging both reject stale activation;
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- graphical and no-window publishers use the same Runtime transaction;
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- removal and terminal teardown converge the active ownership ledger.
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This retires divergence row AD-6. The remaining lost-cell state-machine work is
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deliberately outside this slice.
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