# Cathedral review — DAT-format facts (companion report)

Delivered 2026-08-30 by the DAT-format verification agent (decompiled the
actual `Chorizite.DatReaderWriter 2.1.7` NuGet binary with ilspycmd and
cross-checked against `docs/research/named-retail/acclient.h`). Key facts
for the cathedral synthesis; flagged caveats preserved.

## Sourcing caveats

- Our DAT parser is the CONSUMED NuGet `Chorizite.DatReaderWriter 2.1.7`
  (no vendored source; facts below come from decompiling the exact linked
  DLL).
- `references/WorldBuilder` is an uninitialized submodule in THIS worktree
  (read from the main worktree at a different SHA — flagged).
- `references/ACViewer` does not exist in either worktree (claims about
  ACViewer: UNVERIFIED).

## EnvCell record (read order, decompiled Unpack)

Flags (int) → self-Id (uint, duplicate) → NumSurfaces (byte) → NumPortals
(byte) → NumVisibleCells (ushort) → Surfaces[]（ushort) → EnvironmentId
(ushort) → CellStructure (ushort) → Position (Frame) → CellPortals[] →
VisibleCells[] (ushort) → [HasStaticObjs 0x2] StaticObjects (count +
Stab{Id,Frame}[]) → [HasRestrictionObj 0x8] RestrictionObj.

`EnvCellFlags`: SeenOutside=0x1, HasStaticObjs=0x2, HasRestrictionObj=0x8.
**0x4 is unclaimed.**

Retail cross-check: `CEnvCell : CObjCell` (acclient.h:32072-32091) maps
1:1; retail's `stab_list` lives on the BASE `CObjCell`
(acclient.h:30914-30932) and is the **PVS list of CELL IDS** — NOT placed
objects. The DatReaderWriter `Stab{Id,Frame}` placed-object struct is a
coincidental homonym (zero matches for `Stab` in the named-retail header).

## CellPortal / BuildingPortal

`CellPortal { PortalFlags Flags; ushort PolygonId; ushort OtherCellId;
ushort OtherPortalId; }` — `PortalFlags: ExactMatch=1, PortalSide=2`.
**No 0x4 member anywhere** (package, our code, WorldBuilder, and retail's
own `CCellPortal` decode exactly two semantic fields: portal_side,
exact_match). NOTE: this contradicts the earlier campaign note
"CCellPortal DAT flag 0x4 = leads outside" — the outside link is the
`OtherCellId == 0xFFFF` sentinel, not a flag bit.

- ExactMatch consumers: `PortalVisibilityBuilder.cs:1168-1183` (skips
  reciprocal clip — decomp:433689), Walk factories
  (`WalkBuildingFactory.cs:76`, `WalkCellFactory.cs:94`).
- PortalSide convention: `(Flags & 0x2) == 0 → normal points INTO the
  owning cell` (`CellPortal.cs:23-24`, `PortalInfo.cs:22-44`);
  `WalkCellFactory.cs:93`: `PortalSide = (Flags & 0x2) != 0 ? 0 : 1`.
- `OtherCellId == 0xFFFF` = the outdoor-exit sentinel (18+ consumers);
  the walk world remaps it to `0xFFFFFFFFu`.

`BuildingPortal` (BuildingInfo.Portals) is a DISTINCT dat type — carries
its own **packed StabList of cell ids** (retail `CBldPortal` with
num_stabs/stab_list + `sidedness`). The walk's `WalkBuildingFactory.cs:81`
reads it directly; the older `Wb.BuildingLoader` path DISCARDS it and
recomputes by BFS.

## LandBlockInfo

`NumCells → Objects[Stab] → Buildings[BuildingInfo{ModelId, Frame,
NumLeaves, Portals[BuildingPortal]}] → [flag] RestrictionTable`.
Confirmed field-for-field; consumer `LandblockLoader.cs:69-103`.

## Water / waterfall (part d)

- `LandDefs::WaterType` is COMPUTED client-side from terrain paint (types
  0x10-0x14 WaterRunning..WaterDeepSea); AcDream already computes it for
  physics (`TerrainSurface.cs:92-128`). It is NOT packed in the records.
- `SurfaceTexture.Textures` is a multi-frame list (the structural shape of
  a flip-book animation) but EVERY consumer in both repos freezes one
  fixed index (`Textures[0]`, WB `[^1]`) — **no water/texture animation is
  implemented anywhere**; whether retail animates via this list is
  UNVERIFIED.
- Which object IS "the waterfall" near the cathedral: UNVERIFIED from
  source — two old bug comments treat it as OUTDOOR landscape-alpha
  content (`PortalVisibilityBuilder.cs:730-736`,
  `RetailPViewRenderer.cs:714-726`), consistent with a translucent stab —
  but note the live probes identified the terrace falls PARTICLE owners as
  EnvCell StaticObjects of cell 0xF4180106 (ids 4f418012-15), which is
  the `HasStaticObjs` list above; both can be true (mesh stab outdoors +
  emitter stabs in cells).

## Notable corrections this report makes to campaign lore

1. "DAT flag 0x4 = leads outside" (PV campaign memory) — REFUTED: no 0x4
   exists; outside = OtherCellId 0xFFFF.
2. "stab list" ambiguity — retail stab_list = PVS cell ids on CObjCell;
   placed objects are a different structure; docs/comments conflating the
   two should be read carefully.
3. Building portals carry authored per-portal cell StabLists in the dat —
   the old Wb path recomputes what the dat already provides.