840c1b6442
Four independent decomp studies (Opus 4.8 x2, Sonnet 4.6, external Codex) converge: retail carries the cell through the collision sweep (validate_transition advances curr_cell only on an accepted move, reverts on a block) and commits it in SetPositionInternal — it never re-derives membership from a static resting position. acdream already ports the sweep machinery (sp.CurCellId/CheckCellId, ValidateTransition, CheckOtherCells) but ResolveWithTransition discards the swept cell and re-derives statically via ResolveCellId (PhysicsEngine.cs:909/928) — the root of the 0170<->0031 doorway/cellar ping-pong. The do_not_load_cells prune is secondary (static/cross-cell lists), not the anti-flicker; W2b was doubly misplaced and is reverted. Render: one PView::ConstructView portal traversal over the same cell graph, rooted at the physics current cell; seen_outside (not a dungeon flag) gates landscape; the outside draws through exit portals clipped to the doorway (no blue-hole, no stencil split). Dungeons/interiors share the machinery; "underground" is emergent. Design doc lays out the staged, evidence-first rewrite (Stage 0 diagnostic -> Stage 1 transition-owned membership [visual gate] -> Stage 2 CELLARRAY/prune parity -> Stages 3-5 render root + PView seal + entity clip). Adds the shared research prompt and all four study reports as the grounding record. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
165 lines
12 KiB
Markdown
165 lines
12 KiB
Markdown
# Phase W (rev) — Transition-owned cell membership + PView render pass
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**Status:** design approved 2026-06-02 (user: "go ahead … thorough rewrite"). Supersedes the
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W2b approach (stab-list prune inside the static `ResolveCellId`) and confirms the A8 two-pipe
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abandonment. Behavior-changing across physics + render → visual verification at the Holtburg
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cottage + a dungeon is the acceptance gate.
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**Grounding:** four independent decomp studies (2026-06-02) — Opus 4.8 ×2, Sonnet 4.6, and an
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external Codex pass — converge with no material contradiction. Reports:
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`docs/research/2026-06-02-retail-cell-render-study-{opus48-a,opus48-b,sonnet46,codex}.md`;
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shared brief: `docs/research/2026-06-02-retail-cell-render-research-prompt.md`. Verified against
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live acdream code this session.
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---
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## 1. Root cause (verified, unanimous)
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Retail never re-derives the player's cell from a static resting position. It **carries the cell
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through the collision sweep** and commits it afterward:
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- `CTransition::validate_transition` @ `0x0050aa70` (pseudo_c:272547-272619): advances
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`sphere_path.curr_cell = check_cell` **only on an accepted, moved sub-step** (`:272608-272619`);
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on a block/slide it **restores** `check_cell ← curr_cell` and returns OK (`:272593`). A
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push-back or standing still therefore **cannot** change the cell.
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- `check_cell` is supplied during `CTransition::check_other_cells` @ `0x0050ae50`
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(pseudo_c:272717) → `CObjCell::find_cell_list` @ `0x0052b4e0` (pseudo_c:308742), which builds
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the candidate `CELLARRAY` (current + portal/transit neighbors + outside cells), picks the
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first **interior** cell whose `point_in_cell` contains the sphere center, and applies the
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`do_not_load_cells` prune (`:308829-308867`).
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- `CPhysicsObj::SetPositionInternal(CTransition*)` @ `0x00515330` (pseudo_c:283399-283462)
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reads `sphere_path.curr_cell` and calls `change_cell` @ `0x00513390` **only when it differs**.
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**acdream already ports the sweep machinery faithfully** — `SpherePath.CurCellId`/`CheckCellId`
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exist; `Transition.ValidateTransition` sets `sp.CurCellId = sp.CheckCellId` on accept and
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reverts on block (`TransitionTypes.cs:3404-3434`); `CheckOtherCells` retargets `CheckCellId`
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after a successful other-cell query (`TransitionTypes.cs:2061-2075`, `:1949`). **The defect is
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the consumer:** `PhysicsEngine.ResolveWithTransition` discards the swept `sp.CurCellId` and
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re-derives the cell from the static sphere origin via `ResolveCellId(sp.GlobalSphere[0].Origin,
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…)` on both the OK and partial paths (`PhysicsEngine.cs:909` / `:928`). As the collision
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push-back jitters the origin ±~8 cm across a boundary, that static re-derive flips — the entire
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`0170↔0031` (and `0170↔0171`, cellar) ping-pong.
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**Corollary (Codex):** the `do_not_load_cells` prune is a **secondary** parity/stability feature
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for static/cross-cell lists (`calc_cross_cells_static` @ `0x00515160`), **not** the per-tick
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anti-flicker mechanism. The load-bearing invariant is transition-owned membership. So the
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membership-return fix alone is expected to stop the flicker; the prune is correctness we add
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after. (This makes the shipped W2b doubly wrong — wrong location *and* wrong mechanism — and it
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is reverted.)
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## 2. Target architecture (retail-faithful)
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**One cell graph, one membership authority, render obeys it.**
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1. **Membership is transition-owned.** `ResolveWithTransition` returns the swept `sp.CurCellId`
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(mirroring `SetPositionInternal`), not a post-sweep static re-derive. `ResolveCellId` is
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**demoted** to the seed-only cases that have no transition: spawn / teleport / server cell
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set. The render reads this single membership answer (`CellGraph.CurrCell`).
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2. **`CellTransit` gains `CELLARRAY` parity:** `AddedOutside` / `DoNotLoadCells`, candidate
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list, and the `find_cell_list` `do_not_load_cells` prune + interior-wins pick. Applied when
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building no-load/static lists from an EnvCell origin. (Correctness/parity — not the flicker
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fix.) The `FindTransitCellsSphere` unconditional `exitOutside=true` (`CellTransit.cs:95-123`,
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A6.P5) is re-gated to retail's portal-plane/sphere test (it currently over-admits outside).
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3. **Render roots at the physics current cell + `seen_outside`**, not an independent AABB
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`FindCameraCell`. Mirrors `CellManager::ChangePosition` @ `0x004559b0` (pseudo_c:94601-94682):
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landscape/sunlight/outdoor-ambient stay live iff the current cell is a landcell OR
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`CObjCell::seen_outside` (acclient.h:30929) is set; otherwise landscape is released and
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indoor ambient is used. The 3rd-person camera offset uses a graph/BSP child lookup
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(`CEnvCell::find_visible_child_cell` @ `0x0052dc50`), rooted at the **player** cell (preserves
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the U.4c flap fix), never an AABB reclassification.
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4. **One PView portal traversal** replaces the indoor/outdoor split + stencil pipeline. Port
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`PView::ConstructView` (`0x005a57b0` EnvCell / `0x005a59a0` CBldPortal), `InitCell`
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(`0x005a4b70`), `AddToCell` (`0x005a4d90`), `AddViewToPortals` (`0x005a52d0`), `DrawPortal`
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(`0x005a5ab0`), `DrawCells` (`0x005a4840`). It yields a `cell_draw_list` + a single
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`OutsideView` from one BFS. Convergence is governed by per-cell `portal_view_type.update_count`
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watermarks + a todo list (NOT a fixed cap — this replaces `PortalVisibilityBuilder
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.MaxReprocessPerCell = 4` and closes #102). When `OutsideView.view_count > 0` (an exit portal
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was traversed), `DrawCells` draws `LScape` (terrain/sky/rain) **clipped to the doorway** with
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a conditional depth clear — so the outside is visible through the door and there is **no blue
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clear-color hole**, by construction. No separate inside/outside stencil pass (WorldBuilder's
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`RenderInsideOut` and ACViewer's brute-force are reference-divergent; the decomp wins).
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5. **Entities/particles clip to the visible cell set** (`find_visible_child_cell` + the PView
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draw list), not the world frustum — kills NPC/door/smoke bleed-through.
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**Dungeons/underground are emergent, not flagged.** Indoors = current cell is an EnvCell
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(`id & 0xFFFF ≥ 0x100`). "Underground" = an EnvCell with no `seen_outside` and no exit-portal
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reachability, on a landblock with no meaningful terrain. There is no client `underground`
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boolean. Pure-dungeon landblocks (all terrain heights 0, EnvCells, no buildings — ACE's
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`IsDungeon` heuristic) simply have no landscape to draw; building interiors/cellars with
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`seen_outside` still draw the clipped outdoor view through portals. Same transition + same PView
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machinery for both.
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## 3. Staged plan (evidence-first, lowest-risk first; each behavior-changing stage is visual-gated)
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- **Stage 0 — Diagnostic (zero behavior change).** Add a probe logging, per
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`ResolveWithTransition`, the swept `sp.CurCellId`/`CheckCellId` **alongside** the value the
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static `ResolveCellId` would return. Launch, walk the doorway/cellar. **Prove the swept cell is
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stable where the static one strobes.** If the swept cell is *also* tainted (the `exitOutside`
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over-admission), do Stage 2's `FindTransitCellsSphere` re-gating first. Gate: evidence in hand.
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- **Stage 1 — Transition-owned membership (behavior-changing).** Return `sp.CurCellId` from
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`ResolveWithTransition`; demote the static `ResolveCellId` to the spawn/teleport/server-set
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seed path only. Revert W2b (`2acd8f9`: `DoorwayHoldMargin` + the prune-in-`ResolveCellId`).
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**Visual gate: the `0170↔0031` / `0170↔0171` / cellar strobe stops; collision unchanged.**
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- **Stage 2 — `CELLARRAY` parity + prune (correctness).** Port `AddedOutside`/`DoNotLoadCells` +
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the `do_not_load_cells` prune + interior-wins pick into `CellTransit`; re-gate the `exitOutside`
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over-admission. Conformance tests against cottage/cellar/dungeon golden candidate sets.
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- **Stage 3 — Render root unification (behavior-changing).** Root render visibility at
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`CellGraph.CurrCell` + `seen_outside`; remove the `ACDREAM_A8_INDOOR_BRANCH` split, the AABB
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`FindCameraCell` + grace-frame hack, and `RenderInsideOutAcdream` stencil path. Camera offset
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via child-cell lookup. **Visual gate: no render-branch strobe; landscape policy correct
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indoors/outdoors/dungeon.**
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- **Stage 4 — PView traversal + seamless seal (behavior-changing, the big one).** Implement the
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PView BFS (`update_count` watermark) producing `cell_draw_list` + `OutsideView`; draw landscape
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through the doorway; cap ceilings; fold in the `EnvCellRenderer` inherited-`GL_BLEND` fix
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(memory `render-self-contained-gl-state`). **Visual gate: interior sealed, outside visible
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through the door (sky/rain), no blue-hole, no transparent walls.**
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- **Stage 5 — Entity/particle cell clipping (behavior-changing).** Clip entities/particles to the
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PView visible set. **Visual gate: no NPC/door/smoke bleed-through; entities through a doorway
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remain visible.**
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## 4. Must-port / align (decomp addresses)
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| Area | Functions |
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| Membership commit | `validate_transition 0x0050aa70`, `SetPositionInternal 0x00515330`, `change_cell 0x00513390` |
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| Cell array | `find_cell_list 0x0052b4e0`, `CEnvCell::find_transit_cells 0x0052c820`, `CLandCell::add_all_outside_cells 0x00533630`, `CELLARRAY::add_cell 0x006b4ff0`, `remove_cell 0x006b4e80`, `calc_cross_cells_static 0x00515160` |
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| Render root | `CellManager::ChangePosition 0x004559b0`, `SmartBox::is_player_outside 0x00451e80`, `Position::get_outside_cell_id 0x004527b0`, `find_visible_child_cell 0x0052dc50` |
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| PView | `ConstructView 0x005a57b0`/`0x005a59a0`, `InitCell 0x005a4b70`, `AddToCell 0x005a4d90`, `AddViewToPortals 0x005a52d0`, `DrawPortal 0x005a5ab0`, `DrawCells 0x005a4840` |
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| Structs (acclient.h) | `SPHEREPATH:32625`, `CObjCell:30915`, `CEnvCell:32072`, `CLandCell:31886`, `CCellPortal:32300`, `CBldPortal:32094`, `CELLARRAY:31574`, `portal_view_type:32346`, `seen_outside @ 30929` |
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Cross-checks: ACE `Transition.cs:984`, `PhysicsObj.cs:1171`, `ObjCell.cs:335`, `EnvCell.cs:311`,
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`CellArray.cs:17`; ACViewer render; WorldBuilder `PortalService`/`VisibilityManager` (reference
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base for the Silk.NET implementation, NOT the algorithm).
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## 5. Risks
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- **Verify-before-delete (Codex):** prove the swept cell is correct before removing the static
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re-derive (Stage 0). Keep `ResolveCellId` for the seed-only path.
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- **`exitOutside` over-admission** (`CellTransit.cs:95-123`): could taint the swept cell; re-gate
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in Stage 2 (or Stage 0 if Stage-0 evidence shows taint).
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- **Collision regression (#98 area):** Stage 1 must NOT touch collision math (only the returned
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cell id). Lean on the existing #98 fixtures + cottage-floor-cap regression test.
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- **Render regression:** build the PView traversal as a frame *product* and diff it against the
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current `PortalVisibilityBuilder` output before changing draw order (Stage 4).
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- **Dungeon PVS blowup (#95):** watch the `update_count` convergence on dungeon graphs; the
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watermark/todo model is the retail fix but validate on a real dungeon.
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- **Dungeon vs cottage QA divergence:** pure dungeons draw no terrain; `seen_outside` cellars do.
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## 6. Conformance / acceptance
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- Unit/replay: doorway-stationary "zero cell changes" test at `0xA9B40170↔0xA9B40031`;
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room↔vestibule and cellar-ramp-top cell-change-only-on-accepted-move tests; blocked-wall
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no-cell-change test; golden `CELLARRAY` candidate sets (cottage door, cellar exit, interior
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portal, building entry); PView convergence test (a cell receiving multiple clipped slices);
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doorway `OutsideView` non-empty + sealed-cellar `OutsideView`-empty tests.
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- Visual (decisive, the user): cottage — flicker gone (Stage 1), interior sealed with sky/rain
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through the door, no blue-hole, no transparent walls, no bleed-through (Stages 4-5); a real
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dungeon — sealed, no terrain, traversal converges without blowup.
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- `dotnet build` green; no NEW deterministic test failures vs the documented static-leak baseline.
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## 7. Task decomposition → plan
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Stages 0-5 above map to plan tasks. Stages 0-2 (membership + parity) are one coherent chunk with
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a visual gate after Stage 1. Stages 3-5 (render) are the second chunk; Stage 4 (PView) likely
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warrants its own detailed sub-spec written after the Stage-1 visual gate confirms the membership
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foundation. W2a (`CellGraph.CurrCell` + `ComputeVisibilityFromRoot`) is kept and built upon; W2b
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is reverted.
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