acdream/memory/project_movement_collision_conformance.md

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# Movement & Collision Conformance Crib
## Phase
Active phase: **L.2 - Movement & Collision Conformance**.
Plan: `docs/plans/2026-04-29-movement-collision-conformance.md`.
Roadmap: `docs/plans/2026-04-11-roadmap.md`.
## One-Sentence Framing
B.3 shipped the MVP resolver foundation; L.2 is the holistic conformance
program for physics, collision, buildings, edge/wall sliding, cell ownership,
movement packets, and server correction.
## Active Movement Spine
```text
InputDispatcher / PlayerMovementController
-> MotionInterpreter + local body prediction
-> PhysicsEngine.ResolveWithTransition
-> TransitionTypes + BSPQuery + ShadowObjectRegistry
-> ResolveResult contact/cell state
-> MoveToState / AutonomousPosition outbound messages
-> WorldSession server echo or correction diagnostics
```
## Lane Ownership
- L.2a: truth probes, diagnostics, fixture capture.
- L.2b: movement wire/contact truth, cell id on packets, correction handling.
- L.2c: transition parity, edge-slide, cliff-slide, precipice-slide,
`NegPolyHit`.
- L.2d: `CSphere` / `CCylSphere`, live entity shapes, building object identity.
- L.2e: outdoor seams, `CELLARRAY`, `find_cell_list`, adjacent-cell checks,
`cell_bsp`, building entry/exit boundaries.
- L.2f: real-DAT fixtures and live retail-observer conformance.
## Non-Negotiables
- Grep named retail before changing AC-specific physics or movement behavior.
- Do not treat ACE accepting a position as proof of retail collision parity.
- Do not reintroduce rewrite-from-zero collision guidance. Continue the partial
retail port by L.2 lanes.
- G.3 dungeon/portal delivery waits on L.2e for trustworthy cell/building
ownership.
- L.1 animation work must coordinate with L.2 when root motion or observer
movement changes the predicted body path.
## Shipped Slices
- 2026-04-29: L.2a/L.2b first diagnostic slice. `ACDREAM_DUMP_MOVE_TRUTH=1`
logs `move-truth OUT` for outbound `MoveToState` / `AutonomousPosition` and
`move-truth ECHO` for player `UpdatePosition` echoes, including local/server
delta. `GameWindow` now passes explicit grounded/airborne contact bytes from
`MovementResult.IsOnGround` to both movement packet builders.
- 2026-04-29: L.2e first cell-ownership fix. `ResolveWithTransition` refreshes
outdoor cell ownership from world position during the sphere sweep, so 24m
outdoor seams update low cell ids and full-cell callers crossing landblock
seams get the destination landblock prefix plus the correct outdoor low cell.
- 2026-04-30: L.2c edge-slide plumbing. User live-tested wall-adjacent slide as
acceptable. Local player and remote dead-reckoning now pass retail-default
`ObjectInfoState.EdgeSlide`; `ACDREAM_DUMP_EDGE_SLIDE=1` logs failed
step-down edge cases so the next slice can distinguish missing walkable
polygon context from cliff-slide/NegPolyHit gaps.