Erik 261322b48e fix(physics): #32 L.2c precipice edge-slide context

Port the first retail precipice-slide slice from named retail/ACE: terrain and BSP walkable hits now preserve polygon vertices, failed step-down edges back-probe to rediscover the walkable polygon, and edge-slide can run precipice/cliff slide instead of only hard-stopping.

Adds pseudocode anchors plus regression coverage for terrain polygon context and loaded-terrain boundary edge-slide.

Co-authored-by: Codex <codex@openai.com>

2026-04-30 08:04:37 +02:00

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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

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 and now reports whether walkable polygon context is present before cliff/precipice handling.
2026-04-30: L.2c precipice-slide context. Named retail SPHEREPATH::precipice_slide and ACE Polygon.find_crossed_edge are now captured in docs/research/2026-04-30-precipice-slide-pseudocode.md. Terrain supplies exact walkable triangle vertices, BSP step-down/find-walkable stores world-space walkable vertices for static object tops, and failed step-down edge cases run the retail back-probe before precipice slide. cliff_slide has a first port, but NegPolyHit, CELLARRAY, full cell_bsp, and real-DAT building portal conformance remain open L.2 work.

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