# Cathedral review — retail interior-root frame reconstruction (companion report)

Delivered 2026-08-30 by the decomp-reconstruction agent (BN pseudo-C +
live Ghidra arbitration on 8081 + acclient.h + symbols.json). THE retail
mechanism reference for the synthesis. Condensed; all pc:/address
citations preserved.

## Frame skeleton (interior root)

1. `SceneTool::BeginScene` @0x0043dad0: **full Clear(7) — COLOR+depth+
   stencil — every frame** (pc:68673-68686). `Flip` bumps m_nFrameStamp
   at frame end (pc:428642).
2. `RenderNormalMode` @0x00453aa0: interior camera → optional
   LScape::update_viewpoint (only when viewer_cell->seen_outside,
   pc:92667-71) → DrawInside(viewer_cell) → **unconditional final drain
   FlushAlphaList(0f)** (pc:92687).
3. TWO PView singletons (pc:427800/427813): `indoor_pview` (draw_landscape
   =1) for the root; `outdoor_pview` (0) for building look-ins — look-in
   floods can never re-trigger landscape/clear/seals (their
   outside_view.view_count is always 0; ClipPortals never raises it when
   draw_landscape=0, pc:433666-84).
4. `PView::DrawInside` @0x005a5860: push root view (full viewport) →
   `ConstructView(root, 0xffff)` — PURE CPU flood, draws nothing; exit
   portals merge clipped apertures into outside_view (pc:433662-76,
   cliplandscape=1 @0x00820f4c).

## PView::DrawCells @0x005a4840 — ALL of this inside `ov > 0` (pc:432715):

1. `Render::PortalList = &outside_view`; `LScape::draw` (pc:432718-19).
2. **Full outdoor alpha drain** FlushAlphaList(0f) (pc:432720).
3. `m_nFrameStamp += 1` (pc:432722) — re-arms part dedupe so a part can
   draw in BOTH the outdoor and interior passes of one frame (straddlers
   draw twice; "emit once" is anti-retail).
4. **Gated z-only clear** (pc:432725-32, Ghidra-verified):
   `forceClear(const 0) || portalsDrawnCount != 0` — the counter is
   incremented ONLY by own-depth portal stamps (seals, arg2==0,
   pc:424569-70) → **a ONE-FRAME LATCH: last frame's seals arm this
   frame's clear.** Steady-state vista frames clear every frame; the
   FIRST such frame does not.
5. **Exit seals** (pc:432737-807): per flooded cell (far→near), per view,
   EVERY portal with other_cell 0xffffffff:
   `DrawPortalPolyInternal(poly, 0)` — REAL projected depth,
   DEPTHTEST_ALWAYS + z-write ON (pc:424584), invisible (vertex alpha 0,
   pc:424686), CULL_NONE, CPU-clipped to the current view (pc:424577).
   (Sibling mode arg2==1 = the far-Z PUNCH z≈0.999999, look-ins only;
   does not increment the counter.)

Then UNCONDITIONALLY (even when ov==0):
6. Lighting restore (pc:432811-12).
7. **Cell shells** far→near: DrawEnvCell dedupes per frame stamp — the
   shell draws ONCE, WHOLE; the per-view loop is vestigial for it; no
   view planes applied; correctness = pure z-test (pc:427885-88).
8. **Cell objects** far→near: PortalList = the cell's views →
   DrawObjCellForDummies → shadow parts sorted by CYpt (viewer distance
   to scaled sort_center, insertion_sort @pc:701156-75) →
   CPhysicsPart::Draw — statics, dynamics, AND particle-emitter parts
   through ONE machinery.
9. Final drain (pc:92687) vs interior depth + seal-stamped apertures.

## Clip vs cull (the definitive table)

- CPU polygon-clipped: ONLY portal-chain polys during the flood
  (GetClip @0x005a4320) and seal/punch fans at draw (their own
  polyClipFinish vs the current view, pc:424577, + a ±12 local-XY trivial
  reject pc:424506-50).
- Sphere-vs-view CULLED, whole-drawn: all meshes (statics, dynamics,
  particles' parts) — DrawMesh per view: viewconeCheck(sphere)
  (pc:429295-96); PARTIAL draws WHOLE under that view; a mesh in N views
  submits N times. Building PORTAL pass is cone-exempt (punches always
  attempted; GetClip <3 points is the real stop, pc:429302-10).
- Cached-flag culled: terrain cells via in_view stamped by
  draw_check_blocks @0x00505f80 iterating EVERY view of PortalList
  (blocks wholly outside every exit view skip at pc:267936). Terrain
  polys then draw whole + immediate (landPolysDraw @0x006b7040 — no view
  clip, no alpha list).
- No test at all: EnvCell shell geometry; seal z-behavior (ALWAYS).
- `alwaysDrawObjects = 1` (@0x00820ed4): DrawSortCell runs for EVERY cell
  of a drawn block — the per-part per-view cone check is the real object
  gate (no pixel leak, just CPU).

## The alpha lists (retail)

TWO static FIFO lists, 3000 entries each (Clip @0x00871b10, Alpha
@0x008af370). NO depth key stored, NO sort at flush — order = submission
order; far-to-near correctness comes from the cell walk + per-cell CYpt
insertion sort. Overflow DROPS the subset (pc:424983). Entry routing:
s_AlphaDelayMask (default 0xE) vs the surface mask; bit3 → Clip list.

Flush sites (grep-complete):
| # | Site | Arg | Depth in place |
|---|------|-----|----------------|
| 1 | DrawBuilding @0x0059f30b | 0f FULL | outdoor-so-far (pre-punch) |
| 2 | DrawBlock @0x005a1a07 | 0.75 valve, fires per outdoor cell (BN's `flush>1` guard is a MISREAD — Ghidra: fires when flush<=1.0) | mid-landscape |
| 3 | DrawCells @0x005a4872 | 0f FULL | complete outdoor depth (pre-clear) |
| 4 | RenderNormalMode @0x00453b8b | 0f FULL (final) | interior + seals |
| 5 | CreatureMode::Render (chargen only) | 0f | its own viewport |

## Depth at final drain (interior root)

- Aperture/vista pixels: the SEAL's portal-plane depth (outdoor per-pixel
  depth NO LONGER EXISTS — cleared; outdoor COLOR survives under the
  stamp). Interior alpha fragments behind the portal plane FAIL there.
- Outdoor particles (falls): drawn in the landscape pass, drained at
  site #3 vs outdoor depth. Cone-PARTIAL spill outside the aperture is
  buried because EVERY interior pixel paints after every outdoor drain
  point — protection is pure ORDERING, not depth.

## ShouldDrawParticles @0x0050fe60 — an UPDATE-time gate

Called per emitter from ParticleEmitter::UpdateParticles (physics-side),
NOT during rendering: `ExaminationObject → 1; CYpt > degrade_distance →
0; cell NULL → 0; cell->IsInView()==0 → 0`. On false: SetNoDraw(1),
degraded_out=1 (particles stop updating AND drawing).
- CLandCell::IsInView @0x00532cb0 = the PREVIOUS frame's stamped in_view
  (one-frame-stale gate).
- **CEnvCell does NOT override it** — the slot resolves to the ICF-folded
  constant @0x005269f0 `return 1` (PARTIALLY_INSIDE, PDB-verified): for
  interior emitters the cell test is VACUOUS; distance is the only
  update-time gate; their draw is flood-gated instead.

## Can content outside the flood/exit views draw? NO.

Interior: pure flood membership. Outdoor blocks/cells: in_view under ≥1
exit view. Outdoor parts: per-exit-view sphere-cone in DrawMesh. Building
portal pass cone-exempt but clip-stopped. No distance bypass exists.

## Corrections to campaign docs

1. DrawBlock per-cell flush polarity RESOLVED (fires; 0.75 pressure
   valve) — BN misread.
2. The m_nFrameStamp bump separates the landscape and interior passes of
   ONE interior-root frame; look-ins NEVER bump (outdoor_pview ov==0).
3. NEW: CEnvCell::IsInView = constant PARTIALLY_INSIDE (ICF fold,
   symbols.json 19-name cluster) — not in any FW doc.

## UNVERIFIED (the agent's own list)

The 0xF418 falls emitters' owner (land cell vs EnvCell static — dat
question; note the DAT-geometry companion resolves this: landblock
object-list stabs); z-write during alpha drains; insertion_sort
direction byte-proof; the ±12 reject polarity; GameSky depth behavior.