research(render) Campaign FW0: the frame-walk pseudocode model + decomp appendix
The distilled port-ready model for FW1: camera-cell rooting, the invisible-panel primitive (punch far-Z / seal own-depth, byte-verified constants), the far-to-near landscape walk, the building two-pass portal machinery with its push/pop asymmetry, the interior flood + DrawCells passes, the view machinery, and the constants/struct anchor table. The panel question is resolved: retail DOES draw depth-only portal-polygon panels via DrawPortalPolyInternal - AD-117 re-invented a real mechanism at the wrong site. FW0 is complete: oracle fixtures, replay helper, decomp model. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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docs/research/2026-08-30-fw-walk-pseudocode.md
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# FW0 — the retail frame walk, port-ready pseudocode model (2026-08-30)
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The distilled model FW1 ports from. Sources: the five decomp reads in
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[`2026-08-30-fw-walk-pseudocode-appendix.md`](2026-08-30-fw-walk-pseudocode-appendix.md)
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(BN pseudo-C cross-checked against the Ghidra patchmem decomp wherever
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x87-flag mush demanded it), reconciled against the live traces in
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[`2026-08-30-fw-walk-oracle/`](2026-08-30-fw-walk-oracle/README.md).
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Every function below carries its named symbol + address; the appendix has
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the full extractions with per-function gotchas.
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## 1. The frame root — `SmartBox::RenderNormalMode` @0x00453aa0
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Per frame (via `SmartBox::Draw` → `DrawNoBlit` @0x00454c20, which first
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runs `update_viewer` and skips rendering entirely when `viewer_cell` is
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null):
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```
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if ((viewer.objcell_id & 0xFFFF) < 0x100) { // CAMERA cell is outdoor
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LScape::update_viewpoint(lscape, viewer.objcell_id);
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Render::update_viewpoint(&viewer);
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Render::set_default_view(); // full-screen view
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Render::useSunlightSet(1);
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LScape::draw(lscape); // → §3
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} else { // camera in an EnvCell
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if (viewer_cell->seen_outside)
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LScape::update_viewpoint(lscape, Position::get_outside_cell_id(&viewer));
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Render::update_viewpoint(&viewer);
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render_device->DrawInside(viewer_cell); // → PView::DrawInside, §5
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}
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D3DPolyRender::FlushAlphaList(0f);
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```
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`SmartBox::update_viewer` @0x00453ce0 resolves the camera pose and cell:
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a `CTransition` sphere sweep (the global `viewer_sphere`) from a pivot on
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the player (CameraManager pivot part + offset) toward the camera's sought
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position; `t->sphere_path.curr_cell` becomes `viewer_cell`. Fallbacks:
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`AdjustPosition` on the raw sought position, else camera at the player
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with `viewer_cell = null` (frame skipped). **The frame roots at the
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CAMERA's cell** — proven live by the porch-cam trace.
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## 2. The invisible-panel primitive — `D3DPolyRender::DrawPortalPolyInternal` @0x0059bc90
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The single primitive behind both "punch" and "seal": draws one portal
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polygon as an untextured CULL_NONE triangle fan, **depth-test ALWAYS,
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z-write ON, color alpha 0** (invisible under SRCALPHA/INVSRCALPHA).
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Byte-verified in the raw pseudo-C: `SetDepthBufferMode(DEPTHTEST_ALWAYS,
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(mode>>2)&1)` @0059be02; forced Z `0.999998987f` @0059bf4b.
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- `flag=1` (mode global `maxZ1`=7): every vertex Z forced to
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**0.999998987 (far plane)** — the **PUNCH**: re-opens the aperture's
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depth so look-in content can draw into it.
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- `flag=0` (mode `maxZ2`=6): real projected Z — the **SEAL**: writes the
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portal surface's own depth at the aperture. Only seals increment
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`portalsDrawnCount` (the deferred z-clear trigger).
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- Trivial reject: polygon wholly outside a ±12.0 local-XY box (the
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24 m cell); the reject-loop polarity is an FP-status idiom (`test
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ah,0x44`) BN could not lift — **re-verify polarity at FW1 against the
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binary bytes** before porting.
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- Debug: raising the mode's alpha bit (via the maxZ1/maxZ2 globals,
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.data @0x820e18/0x820e14) renders the panels visibly in cycling colors.
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- Goes through `DrawPrimitiveUP`, gated by the registry bool
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`s_bAllowDrawPrimitiveUP` (default 1).
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- Restores NO state — callers rely on backup/restore_curr_state.
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**This resolves the campaign's panel question:** the "seal panels" are
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not mesh subsets (those authored Translucency-1.0 subsets stay
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never-drawn); they are the buildings'/cells' PORTAL POLYGONS drawn
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depth-only by this primitive. AD-117's stamps unknowingly re-invented a
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real retail mechanism at the wrong site with the wrong geometry.
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## 3. The outdoor walk — `LScape::draw` @0x00506330
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```
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GameSky::Draw(sky, 0) // dome
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LScape::draw_check_blocks(this) // per-view visibility union (below)
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for i = mid_width² - 1 .. 0: // block_draw_list built near-to-far →
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blk = block_draw_list[i] // backwards walk = FAR-TO-NEAR
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if (blk && blk->in_view) render_device->DrawBlock(blk)
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if (weather) GameSky::Draw(sky, 1)
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```
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- Grid: `mid_width`=11 × 11 blocks (`mid_radius`=5); block side 192 m
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(FPU-elided in BN — pinned by the explicit 24 m cell pitch).
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- `get_block_order` @0x00504c50: viewer's block first, then concentric
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rings (8 quadrant-symmetric slots per step from static coefficient
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tables); rebuild only when the viewer crosses a LANDBLOCK boundary.
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- Block frames are **viewer-relative**: origin
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`((row−viewer_b_xoff)·192, (col−viewer_b_yoff)·192, 0)` — the
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landscape renders in viewer-block-local space for float precision.
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- `draw_check_blocks` @0x00505f80: clears every block/cell `in_view`,
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then FOR EACH VIEW of `Render::PortalList` (outdoor: the default view;
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interior: the exit views) unions visibility via clip-height interval
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grids (`get_clip_height` corners → `block_check` vs max/min_zval);
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`landcell_check` @0x005050a0 refines per-cell (non-8×8 far blocks:
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all cells PARTIAL; ENTIRELY_INSIDE blocks: all cells 2; else per-cell
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corner grids at 24 m pitch). A cell marked by an earlier view is never
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downgraded.
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- `CLandBlock::calc_sq_draw_order` @0x0052f4a0: per-block cell order,
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closest cell (picked by the 9-case compass direction switch) written
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LAST, rings filled backwards → forward iteration = far-to-near.
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Early-out compares only `closest.x/y`, not `dir` (keep this quirk).
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Per block, `RenderDeviceD3D::DrawBlock` @0x005a17c0: pass 1 updates
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in-view cells' shadow objects + insertion-sorts shadow parts by depth;
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pass 2 per cell (far-to-near): terrain (`DrawLandCell` — detail texture
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only on full 8×8 blocks) then `DrawSortCell` @0x0059f140:
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```
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if (cell->building) render_device->DrawBuilding(cell->building) // §4
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render_device->DrawObjCell(cell) // scenery/statics/dynamics via sorted shadow parts → CPhysicsPart::Draw(part, 0)
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```
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Mid-walk alpha pressure valve: `FlushAlphaList(flush)` with the global
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`flush`=0.75 (flushes only above ~2250 queued alpha meshes).
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## 4. Buildings — `RenderDeviceD3D::DrawBuilding` @0x0059f2a0
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```
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outdoor_pview->outdoor_portal_list = b->portals; // ALWAYS
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CPhysicsPart::UpdateViewerDistance(part0); // degrade level
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if (part0->gfxobj[deg_level] == 0) return; // degraded out → whole building skipped
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CBuildingObj::curr_pos = &b->m_position; // frame-restore anchor for the portal pass
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set building detail-surface state; FlushAlphaList(0f);
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CPhysicsPart::Draw(part0, 1); // PORTAL pass
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ObjBuildingOrBuildingPart = 1;
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CPhysicsPart::Draw(part0, 0); // SHELL pass (normal mesh; per-frame dedupe applies)
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ObjBuildingOrBuildingPart = 0;
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```
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The portal pass, through `DrawMesh` @0x005a0860 (per portal view,
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`building_view`-gated; portal-flagged draws run even when viewconeCheck
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says OUTSIDE) → `DrawMeshInternal` @0x0059f360, walks the building's
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drawing-BSP **twice** (`BSPTREE::build_draw_portals_only` — portal nodes
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visited far-to-near, plane epsilon 0.0002):
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- **Pass 1 — punch.** Each in_portal → `PView::DrawPortal` @0x005a5ab0 →
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`ConstructView(CBldPortal)` @0x005a59a0: viewer sidedness must match
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the authored `portal_side` (IN_PLANE within ±0.0002 fails BOTH gates);
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`GetClip` must leave ≥3 points; the destination EnvCell must be
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currently Visible (`CEnvCell::GetVisible` — not loaded ⇒ silently no
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punch, no fallback). On success: `DrawPortalPolyInternal(poly, 1)` —
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the far-Z punch — and the clipped view is pushed onto the destination
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cell's top `portal_view` via `Render::copy_view`.
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- **Pass 2 — look-in.** Same walk/gates; on success recurses
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`ConstructView(CEnvCell)` (the §5 flood seeded through
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`other_portal_id`) and calls `PView::DrawCells` — the trace's
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`DC ov=0` punches: interior cells + objects drawn into the punched
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aperture (no landscape, no clear, no sealing on this path).
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- Push/pop asymmetry (MUST preserve): `ConstructView(CBldPortal)` pops
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the building frame only on SUCCESS (before recursing); on failure the
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frame stays pushed and `DrawPortal` compensates by re-pushing
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`CBuildingObj::curr_pos` only on success.
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- `DrawCells` bumps `m_nFrameStamp`, re-arming the per-frame part dedupe
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so objects already drawn outdoors can draw again inside a look-in.
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- DEAD in 2013 (do not port): `DrawBuildingLeaf` + `curr_leaf_cells`
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(pre-EnvCell interior model); `PView::DrawPortal`'s pass==3
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seal-on-fail branch (pass only ever ∈ {1,2}).
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## 5. Interior frames — `PView::DrawInside` @0x005a5860
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```
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CEnvCell::curr_view_push(cell); // num_view++ (0x48-byte lazy slot, counters reset)
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PView::add_views(this, cell->num_stabs, cell->stab_list); // push a view slot on every visible stab cell
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Render::positionPush(3, identity Position stamped with cell DID);
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Render::copy_view(cell->top_view, null, 4); // root view = full viewport quad
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PView::ConstructView(this, cell, 0xffff); // the flood (below)
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PView::DrawCells(this, 0); // dead arg
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Render::positionPop(); remove_views(...); cell->num_view -= 1;
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```
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`ConstructView(CEnvCell)` @0x005a57b0 — the flood: zero
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`outside_view.view_count`, bump `master_timestamp`, reset todo/draw
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lists; seed `InitCell(cell, 0xffff)` + `InsCellTodoList(cell, 0)`;
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then pop-from-END: append cell to `cell_draw_list` (grow +30), mark top
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view `cell_view_done`, `ClipPortals` → `AddViewToPortals` (clips each
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portal against the cell's current view and enqueues neighbors with their
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clipped views; portals leading outdoors raise `outside_view`).
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`PView::DrawCells` @0x005a4840 — the draw, all passes far-to-near
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(`cell_draw_list` walked from the end):
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```
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if (outside_view.view_count > 0) { // 'ov' in the traces (field, not the dead arg)
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Render::PortalList = &outside_view;
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LScape::draw(lscape); // landscape THROUGH the exit views (§3)
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FlushAlphaList(0f); m_nFrameStamp += 1;
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if (forceClear || portalsDrawnCount != 0) // count reset only on the !forceClear arm
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Clear(flag 4 /*z-buffer*/, black, z=1.0); // deferred clear triggered by earlier SEALS
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for cells far-to-near, per view of the cell's top portal_view:
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for each portal with other_cell_id == 0xFFFFFFFF: // exits to the landscape
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DrawPortalPolyInternal(portal.poly, 0); // SEAL @ own depth (verified @0059a49b7)
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}
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useSunlightSet(0); restore_all_lighting();
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for cells far-to-near, per view: setup_view; DrawEnvCell(cell); // BSP geometry
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for cells far-to-near: PortalList = cell top view; DrawObjCellForDummies(cell); // objects
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```
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Degenerate guard NOT to port: `num_view==0` would loop 65535 views —
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unreachable (every listed cell was `curr_view_push`ed).
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## 6. View machinery
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- `Render::set_view` @0x0054d0e0 — pure CPU global install: the active
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view's edge count, in-mask (`npnts+1` bits: edges + the CY plane),
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vertex/plane base, screen bounds. No GPU state.
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- `Render::copy_view` @0x0054dfc0 — appends ONE view: perspective-divided
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screen points (drop near-duplicates/collinear within ~1 px; <3
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survivors ⇒ reject; cap 31), bounds, and per-edge WORLD-space planes
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(`N = normalize(cross(ray_i, ray_i+1))`, `d = −dot(N, viewpoint)`).
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`copy_view(dest, null, 4)` = the full-viewport root quad.
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- `PView::GetClip` @0x005a4320 — projects the portal polygon
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(`xformStart`), reverses winding for NEGATIVE side, and (do_clip)
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clips via `ACRender::polyClipFinish` against the installed view. ≤32
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verts assumed. The only CPU polygon clip in the frame.
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- `Render::viewconeCheck` @0x0054c250 — sphere vs the CY plane + the
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active view's edge planes, in viewer-block space. Cull strict
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(`d < −r`); partial inclusive (`d ≤ r`); publishes
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`local_object_center/radius` ALWAYS (even when OUTSIDE). BN's version
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of this body is unusable (inverted flags) — the model here is
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Ghidra-verified.
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## 7. Constants and anchors
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| Item | Value |
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|---|---|
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| Outdoor cell test | `(objcell_id & 0xFFFF) < 0x100` |
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| Plane/side epsilon `F_EPSILON` | 0.000199999995f (0x3951B717) |
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| Punch far-Z | 0.999998987f |
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| Panel depth mode | test ALWAYS, write ON (mode bit2), alpha 0 |
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| Panel local-XY reject box | ±12.0 |
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| Landscape grid | mid_width 11, mid_radius 5, block 192 m, cell 24 m |
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| Alpha pressure valve | global `flush` = 0.75 (~2250 meshes) |
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| copy_view vertex cap | 31 (0x1F) |
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| Flood list growth | +30 (0x1E) |
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| BoundingType | 0 OUTSIDE, 1 PARTIALLY_INSIDE, 2 ENTIRELY_INSIDE |
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| Sidedness | 0 POSITIVE, 1 NEGATIVE, 2 IN_PLANE (always rejects) |
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| Exit-portal sentinel | `other_cell_id == 0xFFFFFFFF` (cell), `0xFFFF` (no-through seed) |
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Struct anchors (acclient.h): `PView` {outside_view@0 (view_count@+0x38),
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draw_landscape, outdoor_portal_list, cell_draw_list@+0x50,
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cell_draw_num@+0x60, cell_todo_list, cell_todo_num, lscape@+0x78};
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`CEnvCell.m_DID`@+0x28, `num_view`@+0x134, `portal_view`@+0x138;
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`CCellPortal` stride 0x18 {other_cell_id, other_cell_ptr, portal@+8,
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portal_side, other_portal_id, exact_match}; `CBldPortal` {portal_side,
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other_cell_id, other_portal_id, exact_match, num_stabs, stab_list};
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`CLandBlock.in_view`@+0xFC, `CLandCell` stride 0x108 (in_view@+0x104).
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## 8. What the traces + code jointly prove about #456
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Outdoor frames draw EVERYTHING distance-eligible — the far building
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first (far-to-near) — and correctness is pure depth: nearer terrain,
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shells, punches, and look-in cell geometry bury the vista. Interior
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frames never roster the far building (exit-view cone culls it) and SEAL
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their exit apertures at own depth after drawing the landscape through
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them, so nothing drawn later can leak into the aperture. There is no
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hiding mechanism to invent; FW3/FW4 reproducing this walk resolves #456
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wholesale.
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## 9. Verification status
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Byte-verified against the raw pseudo-C by hand: the seal loop
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(`other_cell_id==0xffffffff → DrawPortalPolyInternal(poly,0)` @0059a49af),
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the deferred z-clear (@005a48a9), `DEPTHTEST_ALWAYS` + z-write-from-mode
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(@0059be02), punch Z 0.999998987f (@0059bf4b), the fan submit (@0059bf84).
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Ghidra-arbitrated where BN mush was flagged: the rooting condition, the
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`viewconeCheck` comparisons, the ConstructView sidedness decode, the
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DrawCells dead argument. **Re-verify at FW1 before relying on:** the ±12
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reject polarity in `DrawPortalPolyInternal` (FP-status idiom), the
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`DrawBlock` alpha-flush comparison polarity, and `InsCellTodoList`'s
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insert position (LIFO pop order depends on it — port it from its body
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@0x005a4f50, not from assumption). Resolved non-issue: the trace's `ov`
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is the FIELD `outside_view.view_count` (probe read PView+0x38), not
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`DrawCells`' dead argument — reports 2 and 5 agree once combined.
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