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acdream/docs/research/2026-07-06-137-corridor-phantom-pickup-prompt.md
Erik e8651b3819 fix #137 (corridor phantom resolved): slide_sphere opposing branch returns Collided; the 'wall' was synthetic 
The mechanism-1 theory (PortalSide portal polys solid in our physics set)
is REFUTED for the corridor repro, and the remaining half of the phantom
is fixed — no cdb session needed:

- The live hit normal (-1.00,0.03,-0.03) matches NO dat polygon: a
  world-space sweep of both seam cells + every portal-adjacent neighbor
  (CorridorSeam_FindPolygonMatchingLiveHit) returns zero candidates. The
  normal is the negated movement direction — the SYNTHETIC value
  slide_sphere's opposing-normals branch records (reversed = -gDelta).
- Cell 0x8A02016E has IDENTITY rotation (the prior session's 'rotation
  maps the portal planes into the -X wall' was a misattribution). The
  PortalSide polys to 0x011E are +-Y planes 1.4 m beside the player's
  track, perpendicular to the +X run — pos_hits_sphere's directional
  cull rejects them for that movement. They ARE referenced by the dat's
  physics-BSP leaves (CorridorCell_PhysicsBspLeafMembership), so retail
  tests them too when approached into their plane; the dat's
  keep-PortalSide / strip-ExactMatch asymmetry reads as intentional
  (solid window/grate-class portals). No portal-poly filter — exactly
  the blanket-skip the pickup warned against.
- Port fix: CSphere::slide_sphere's opposing-normals branch
  (0x005375d7-0x0053762c) records the reversed displacement and returns
  COLLIDED_TS; our port returned OK ('retail returns OK here' was a
  decomp misread), letting the step complete as-is with the synthetic
  collision normal that validate's epilogue then persisted as the
  sliding normal the wedge absorbed on. TransitionTypes opposing branch
  now returns Collided; pinned by
  SlideSphere_OpposingNormals_ReturnsCollided_WithReversedDisplacementNormal
  (RED->GREEN).
- Dat-backed replay (Issue137CorridorSeamReplayTests) reproduces the
  live hit frame verbatim (same in/out to the millimeter, same 016E->017A
  transit, same +8mm settle) and runs the corridor CLEAN: hit=no, no
  sliding normal persisted, six further forward frames advance freely.
- Inspection tests extended: physics-BSP leaf membership walk +
  hit-normal candidate sweep + downward-poly sweep (all report-style,
  dat-gated). Pickup prompt banner'd SUPERSEDED; ISSUES #137 updated
  (door half stays open); audit doc extended with the resolution.

Suites: Core 2551 / App 713 / UI 425 / Net 385, 0 failures.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-05 18:27:40 +02:00

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Pickup prompt — #137 corridor phantom collision (paste into a fresh session)

SUPERSEDED 2026-07-06. The corridor phantom is FIXED (visual gate pending) — see docs/research/2026-07-06-137-sliding-normal-lifecycle-audit.md. Mechanism 2 was real (BSPQuery stub slide responses leaked sliding normals; fixed). Mechanism 1's framing was WRONG: the recorded wall normal was SYNTHETIC (slide_sphere's opposing branch + a return OK vs retail's COLLIDED_TS misport — fixed); the PortalSide polys are ±Y planes perpendicular to the run, directionally culled, tested by retail's own BSP leaves too, and plausibly legitimately solid (window/grate class). The step −1 cdb session below is NOT needed for this repro. Kept for the audit trail only.

Read claude-memory/project_physics_collision_digest.md FIRST (binding DO-NOT-RETRY table), then ISSUES #137 (the 2026-07-05 CHARACTERIZED section — the full evidence chain lives there), then this file. The 2026-07-05 session's ledger for context: #172 (CCylSphere family port), #173 (remote ceiling bounce), #174 (motion-queue drain — doors work after jumping), #175 (door collision at the motion-table closed pose, two takes).

The bug (user-verified repro, Facility Hub 0x8A02): running down a corridor, an INVISIBLE blocker stops the player mid-corridor; the player can walk around it. Two stacked mechanisms, both evidence-pinned:

Mechanism 1 — PortalSide portal polygons are solid for us

  • Live: crossing corridor cells 0x8A02016E → 0x8A02017A at world x≈85.25 recorded ONE wall hit, normal (−1,0,0) — straight against the movement (launch-175-verify2.log:42858, worktree root).
  • Dat (Issue137CorridorSeamInspectionTests, committed): cell 0x8A02016E's three portals to 0x011E (polys 1/3/5, flags=PortalSide, NOT ExactMatch) are PRESENT in CellStruct.PhysicsPolygons; every ExactMatch portal in the same cell is absent from the physics set. The cell's rotation maps those portal planes into the world −X wall the player hit.
  • Oracle greps DONE (do not repeat): CCellStruct::UnPack 0x00533d00 loads physics polys + BSP verbatim (no portal stripping); CPolygon::pos_hits_sphere/hits_sphere/polygon_hits_sphere_slow_but_sure (0x005394f0/0x00539540/0x00538a10) are pure geometry; CCellPortal (0x0053bab0) carries portal→CPolygon + portal_side + exact_match but the BSP test chain never consults it.
  • NEXT (step −1 protocol, needs the user): cdb-attach a live retail client at this exact corridor (Facility Hub, the 016E↔011E portals) and trace which path lets retail through: breakpoint BSPTREE::find_collisions / BSPLEAF::sphere_intersects_poly / CPolygon::pos_hits_sphere and see whether the portal polys are ever TESTED (candidate A: sidedness/stippling — the polys carry stip=NoPos — or the pos_hits_sphere tail's directional cull) or never REACHED (candidate B: transit/membership order hands the sphere to the neighbor cell whose geometry has a real hole). Toolchain crib: claude-memory/project_retail_debugger.md + the CLAUDE.md "Retail debugger toolchain" section. Verify the binary with py tools/pdb-extract/check_exe_pdb.py first.
  • ⚠️ Do NOT ship a "skip portal polys in the physics BSP" filter on assumption — if retail's answer is sidedness or test order, a blanket skip opens holes (some PortalSide polys may be legitimately solid from one side — one-way drops etc.).

Mechanism 2 — the sliding-normal absorbing wedge (fix independently)

  • After the single seam hit, EVERY forward resolve returns ok=False hit=no with zero advance: the body-persisted SlidingNormal (−1,0,0) projects the +X offset to exactly ZERO in Transition.AdjustOffset, and the stepping loop's abort-small-offset fires at step 0 (TransitionTypes FindValidPosition loop, return i != 0 && …) — BEFORE any collision test could refresh the state. An ABSORBING wedge; strafing escapes it (the user's "push through on the side").
  • Retail re-derives slide state per frame — OBJECTINFO::get_object_info pc:279992 "governs only the NEXT frame" (#116 notes in the digest). AUDIT: who writes the body's persisted SlidingNormal (PhysicsEngine.ResolveWithTransition seed ~:995-1040 + the writeback), and where retail CLEARS it when contact does not recur. This is the #116 slide-response family — check ISSUES #116 before changing anything (oracle-first; the digest's DO-NOT-RETRY table applies).
  • Likely the bigger playability win: without the wedge, mechanism 1 alone would be a momentary stutter, not a dead stop.

Order: mechanism 2 first (pure acdream-side audit + fix, testable with a replay-style unit test: seed a body with a stale sliding normal, resolve forward with no obstruction in range, assert the step is NOT zeroed), then the mechanism-1 cdb session when the user can run retail side-by-side.

Gotchas: PowerShell Tee logs are UTF-16 (tr -d '\000' before grep); the user manages client lifecycle; probes RESOLVE/CELL/BUILDING are DebugPanel-toggleable (ACDREAM_DEVTOOLS=1); the [shape-pose] line (ACDREAM_DUMP_MOTION=1) prints each BSP registration's pose source. Register rows to touch if fixes ship: none exist yet for either mechanism — add per the same-commit rule; #116's row interactions per the digest.