fix #124: interior-root building look-ins as a landscape-stage sub-pass

From inside a building, looking out at ANOTHER building with an opening
showed its back walls missing (see-through to the world): per-building
look-in floods only ran for outdoor roots; under an interior root the
far building's interior never flooded.

Decomp anchor (named-retail, this session's read): retail runs the
look-in INSIDE the landscape stage for ANY root - LScape::draw is the
FIRST call of PView::DrawCells' outside-view branch (pc:432719),
strictly BEFORE the depth clear (pc:432732) and the exit-portal seals
(pc:432785). ConstructView(CBldPortal) (0x005a59a0) clips each aperture
via GetClip against the INSTALLED view - the accumulated doorway region
when looked into from inside - and build_draw_portals_only pass 1
far-Z punches ALL apertures before pass 2 floods + draws any interior
cell. The nested DrawCells has an empty outside view (PView ctor
draw_landscape=0): no recursive landscape/clear/seal.

Port:
- GameWindow's per-building gather (frustum pre-gate on
  Building.PortalBounds) now runs for interior roots too; the root's
  own doorway self-excludes via the seed eye-side test (the eye is on
  its interior side).
- PortalVisibilityBuilder.BuildFromExterior/ConstructViewBuilding gain
  seedRegion - the installed-view clip: interior-root look-ins seed
  against the OutsideView polygons (a building not visible through the
  doorway never floods); null = full screen (outdoor roots unchanged).
- RetailPViewRenderer.DrawBuildingLookIns: a landscape-stage sub-pass
  (before ClearDepthForInterior + seals) - per building, punch ALL
  apertures (new DrawLookInPortalPunch callback, always forceFarZ=true,
  closing the ISSUES "forceFarZ keys on root kind, under-punches" gap),
  then draw the flooded cells' shells + statics far->near. Look-in
  frames are NEVER merged into the main frame: a merged cell would draw
  post-clear and z-fail against the root's seal (the old ledger
  portShape sketch was wrong on this point).
- Look-in cells join the Prepare + partition set so shells have batches
  and statics route to ByCell (consumed only by the sub-pass; the main
  cell-object pass iterates the main flood's cells).

Register: AP-33 added in the same commit - look-in statics draw WHOLE
(no per-part viewcone; over-include is the safe direction) and look-in
DYNAMICS are deferred (an NPC inside a far building stays invisible -
retail draws objects per overlapped cell in the landscape stage).

Pins: Issue124LookInSeedRegionTests on the real corner-building door -
a seed region containing the aperture floods (and never more than the
full-screen seed), a disjoint region floods NOTHING, and an
interior-side eye never seeds its own exit portal.

Suites: App 259+1skip / Core 1439+2skip / UI 420 / Net 294 green.
Awaiting the user gate: far-building interiors visible through their
apertures from inside; #130 re-gate (top-edge strip) rides the same
launch.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/ISSUES.md

@@ -4304,28 +4304,48 @@ of which draw list the building's shell left.
 
 ## #124 — Looking out through an opening: far buildings with openings show missing/transparent back walls
 
-**Status:** OPEN
+**Status:** FIX SHIPPED — awaiting user visual gate
 **Severity:** MEDIUM
-**Filed:** 2026-06-11 (re-gate; pre-existing — "still have that issue")
+**Filed:** 2026-06-11 (re-gate; pre-existing — "still have that issue";
+user 2026-06-12: "especially visible when I look out through a door
+opening when inside a building")
 **Component:** render — per-building look-in floods under INTERIOR roots
 
 From inside a building, looking out through a door/window at ANOTHER
 building that has an opening: the far building's back walls are
-missing/transparent (see the world through it). **Lead (by read):** the
-per-building look-in floods (`MergeNearbyBuildingFloods`) run ONLY for
-outdoor roots — `RetailPViewDrawContext.NearbyBuildingCells` is
-documented "Null for interior roots." So under an interior root the far
-building's INTERIOR never floods: through its window you see the shell
-only, and a shell has no interior back-wall faces → transparent.
-Retail runs the building look-in inside `LScape::draw` (DrawBlock →
-DrawPortal → ConstructView(CBldPortal)), which executes for ANY root
-whose outside view is non-empty — including interior roots looking out
-a doorway. Fix shape: provide the nearby-building gather + per-building
-floods for interior roots too, with look-in apertures getting PUNCH
-semantics (the `forceFarZ` selector currently keys on
-`clipRoot.IsOutdoorNode`, which under-punches this case). Needs its own
-focused pass — touches the gather, the merge, and the depth-mask
-selector.
+missing/transparent. The lead confirmed by decomp: retail runs the
+look-in INSIDE the landscape stage for ANY root — `LScape::draw` is the
+FIRST call of `PView::DrawCells`' outside-view branch (pc:432719),
+strictly BEFORE the depth clear (pc:432732) and the seals (pc:432785);
+`ConstructView(CBldPortal)`'s GetClip runs under the INSTALLED view
+(the doorway region), and all apertures far-Z punch (pass 1) before any
+interior cell draws (pass 2).
+
+**Fix (2026-06-12):**
+- The per-building gather (frustum pre-gate on `Building.PortalBounds`)
+  now runs for interior roots too; the root's own doorway self-excludes
+  via the seed eye-side test.
+- `BuildFromExterior` gained `seedRegion` — the port of retail's
+  installed-view clip: interior-root look-ins seed clipped against the
+  OutsideView (doorway) polygons, so a building not visible through the
+  doorway never floods. Outdoor roots keep the full-screen default.
+- NEW `DrawBuildingLookIns` sub-pass inside the LANDSCAPE stage (before
+  the depth clear + seals): per building, punch ALL apertures
+  (`DrawLookInPortalPunch`, always far-Z), then draw the flooded cells'
+  shells + statics far→near. NOT merged into the main frame — a merged
+  cell would draw post-clear and z-fail against the root's seal.
+- Look-in cells join the Prepare/partition set (shells get batches,
+  statics route to ByCell, consumed only by the sub-pass).
+
+Pins: `Issue124LookInSeedRegionTests` (containing region floods ⊆
+full-screen flood; disjoint region floods nothing; interior-side eye
+never seeds its own exit door). Register: AP-33 (look-in statics drawn
+whole — no per-part viewcone; look-in DYNAMICS deferred — an NPC inside
+a far building stays invisible; both documented).
+
+**Gate:** from inside a building, look out the door at another building
+with an open door/window — its interior/back walls render through its
+aperture instead of see-through to the world behind.
 
 ---
 

docs/architecture/retail-divergence-register.md

@@ -92,7 +92,7 @@ accepted-divergence entries (#96, #49, #50).
 
 ---
 
-## 3. Documented approximation (AP) — 32 rows
+## 3. Documented approximation (AP) — 33 rows
 
 | # | Divergence | Where (file:line) | Why it is safe / justified | Risk if assumption breaks | Retail oracle |
 |---|---|---|---|---|---|
@@ -128,6 +128,7 @@ accepted-divergence entries (#96, #49, #50).
 | AP-30 | AutonomousPosition diff cadence compares with epsilons (1 mm pos, 1e-4 normal, 1 mm dist); retail's `Frame::is_equal` is an exact float compare | `src/AcDream.App/Input/PlayerMovementController.cs:1541` | Sub-millimeter epsilon is well below any movement worth suppressing; comparisons are against last-SENT state so drift accumulates past the epsilon | Sub-epsilon drift suppresses an AP send retail would have made — negligible today; a consumer expecting retail's exact send-on-any-change cadence sees fewer packets | `Frame::is_equal` pc:700263 |
 | AP-31 | Scenery placement drift + the 0xA9B1 road-edge tree — WB-upstream divergences from retail, ACCEPTED (**#49/#50**, 2026-05-11) | `src/AcDream.Core/World/SceneryGenerator.cs` (via `WbSceneryAdapter`) | Piecemeal patching against WB upstream is net-negative (the `e279c46` road-check attempt over-suppressed scenery elsewhere, reverted `677a726`); visible impact = a handful of trees a few meters off | The same WB-upstream class could hide a *larger* placement divergence elsewhere; revisit only via a coherent ACME-style per-vertex filter port | `CLandBlock::get_land_scenes`; ACME GameScene.cs:1074 per-vertex road filter |
 | AP-32 | Cell shells DRAW +0.02 m above the dat EnvCell origin (`ShellDrawLiftZ`, z-fight vs coplanar terrain); retail draws at the origin verbatim. Split invariant: PHYSICS + visibility graph UNLIFTED (f35cb8b, **#119**-residual), every DRAW-space consumer of portal/cell geometry LIFTED (OutsideView color gate via `Build(drawLiftZ)`, seal/punch fans — **#130**) | `src/AcDream.App/Rendering/GameWindow.cs:5604` (const at `PortalVisibilityBuilder.ShellDrawLiftZ`) | Shell floors coplanar with terrain z-fight in our z-buffered frame; the 2 cm lift is the documented stand-in | A new draw-space consumer of portal/cell polygons that forgets the lift re-opens a 2 cm seam at horizontal aperture edges (the #130 top-edge strip, ~7 px at 2.4 m); a visibility consumer that picks up the LIFTED transform re-opens the #119-residual horizontal-portal side-cull | retail draws cell geometry at the dat EnvCell origin (no lift) |
+| AP-33 | Interior-root look-in statics (**#124** sub-pass) draw WHOLE — no per-part viewcone check; retail viewconeCheck's each part vs the installed view. Look-in DYNAMICS are not drawn at all (deferred; retail draws objects per overlapped cell in the landscape stage) | `src/AcDream.App/Rendering/RetailPViewRenderer.cs` (`DrawBuildingLookIns`) | The main viewcone has no entries for look-in cells; over-include is the safe direction (z-correct, repainted outside apertures by the root's shells); look-in cell counts are small (~1-3 cells) | Statics: a few wasted draws only. Dynamics: an NPC inside a far building seen through two openings is invisible where retail shows it | `viewconeCheck` 0x0054c250; nested `DrawCells` objects pc:432878 |
 
 ---