docs: findings/backlog through D280 (v0.2.1 batch + D236 tree-wall passes 2-9)

Records the v0.2.1 hotfix batch (D259-D264, this commit's code) and the
ongoing D236 Surface-1 tree-wall investigation (D265-D280): still open as of
D280 -- fog math verified N64-faithful, the noise class confirmed as the
weave's painter, the portal-culling over-draw fix (D271) real but
insufficient, no quick win identified. The D266-D280 probe code and the
D266 IA4 decode / portal-culling fixes themselves stay uncommitted pending
the game-wide regression sweep GRAPHICS-BACKLOG.md flags.

Claude-Session: https://claude.ai/code/session_01KwZViAFaXua3PKgHHjNgvi

docs/dev/GRAPHICS-BACKLOG.md

@@ -25,7 +25,7 @@ once the game is playable start-to-finish without crashes.
 | ~~**D233**~~ | ~~All levels (intermittent): near doors — especially doors you can't see through to the inside — the indoor level geometry vanishes and you can see straight through it into the room, while world objects (computer terminals, furniture) in that space still draw.~~ | **FIXED + VISUALLY VERIFIED (M-107 fix, M-108 verify).** `port/fast3d/gfx_pc.cpp` `gfx_sp_tri1` was trivial-rejecting visible triangles that had a behind-camera (`w<0`) vertex. Status cell here was stale at "not investigated" — corrected M-119. §F D233. |
 | ~~**D234**~~ | ~~Dam: the guard towers along the actual dam structure are invisible except for the first one.~~ | **FIXED + VISUALLY VERIFIED (M-108).** Same underlying mechanism as D233. Status cell here was stale at "not investigated" — corrected M-119. §F D234. |
 | **D235** | Wrong textures load after dying/restarting a level — clarified: not Facility-specific, seen on multiple levels; trigger is death/restart (level reload), not a general build regression. | **Observed, not investigated** (M-106, user QA report, clarified same session). This is a state-leak on level re-entry, not a one-level texture-decode bug — prime suspect is the texture pool / CI-cache (D217/D228 neighbourhood) not fully resetting between a level teardown and reload (stale arena base, a palette-cache entry keyed by a reused address, or a texpool index not rewound). Needs: confirm it does NOT repro on a fresh level boot (only after death/restart); which surfaces; a screenshot. Next: instrument `texInitPool`/the CI-cache clear path for what does/doesn't reset on reload vs cold boot. | 
-| **D236** | Surface 1: the 2D billboard trees that appear at the start of the level and around the map don't draw as discrete tree sprites — they render as a wall/sheet of tree texture instead of the proper 2D tree objects. | **Observed, not investigated** (M-106, user QA report). Billboards = camera-facing quads; "wall of tree texture" reads as either (a) the billboard orientation/quaternion missing so all quads emit coplanar in world space, or (b) a UV/texture-rect setup error mapping the whole sheet onto each quad. Distinct from D176(b)'s tree-*line* backdrop static (that's the painted perimeter wall; this is discrete 2D tree objects). First checks: `GE_PCDUMP` at the Surface 1 opening; inspect one tree billboard's emitted vertices + texture coords in fast3d; check whether the quads are camera-facing on N64 reference footage. |
+| **D236** | Surface 1: the 2D billboard trees that appear at the start of the level and around the map don't draw as discrete tree sprites — they render as a wall/sheet of tree texture instead of the proper 2D tree objects. | **OPEN — second pass active (D266–D269); first-pass decode fix was reverted after a negative user re-test (D265)** (M-106, user QA report). The earlier IA16 framing was a misidentification: the cards are flat quads by design (no billboard opcode; byte-matched ROM emission) and bind an opaque IA8 64×16 strip plus an alpha-blended **IA4 128×16** strip (texdump r117) that is a row of ~13 faint conifer silhouettes. The wall came from `import_texture_ia4` decoding the RDP's I2:A2 nibble as I3:A1 — A2=1 canopy pixels went fully opaque, A2=2 dithering vanished (bug inherited verbatim from the PD port). **Second pass (D266–D269) re-framed the bug: the visible wall band is CI8 32×32 gradient/blob cards, not IA at all** — two draw classes per room stream (OPA + XLU), BILERP/TEXTLOD/2-cycle/**FOG-on**; texel-alpha blending proven correct by force-alpha A/B (D268). Current ranked suspects: fog range/application (D218 family) > TEXTLOD/mip sampling > draw density/culling > palette. The I2:A2 decode + AC-aware edge fixes are re-applied in-tree (uncommitted) and still owe a game-wide IA4 regression sweep before commit. |
 | **D249** | Streets and Egyptian (the two biggest/most-open levels) show culling problems on far-away geometry at *default* FOV — distant geometry drops/pops incorrectly. Also a QoL ask: improve LOD in general, but gate it behind a toggle so N64-accurate ("old school") LOD stays selectable. | **Observed, not investigated** (M-119, user QA report). Distinct from D222 (high-FOV near-edge culling) and D218 (fog/far-clip tint). Two candidate mechanisms: (a) portal/room-visibility cutting off too aggressively at range on large multi-room layouts (D233/D234 neighbourhood — check for a far-plane/depth-range sibling to D233's w<0 trivial-reject fix), or (b) GE's own LOD/detail-swap system not ported faithfully (mip-tile / simple-model substitution at distance, `gfx_lod_tile_offset` family). First checks: `GE_PCDUMP` a long sightline on Streets/Egyptian where geometry visibly pops; determine which of (a)/(b) is firing before designing the fix or the requested toggle. §F D249. | 
 | **D217** | 1P weapon viewmodel + character-model CI textures render with a wrong palette on many levels / multiple weapons — PP7 grip + hand render flat green on Facility & Depot, "weird or missing" gun textures elsewhere; Bond's watch face too. Surfaced by D215 (viewmodel now draws). Clean on Bunker1. | **Defect ① FIXED (M-90), pending human playtest eyeball — full detail in `findings.md` §H "D217 — M-90" and §F D217.** Root cause: weapon texpool arena bases land %8==4 on PC (memp bump drift from pointer bloat); `texAlignIndices` absolute 8-byte row padding then shifts every palette 4 bytes early while model-DL `G_LOADTLUT` reads the N64 offset (grip count=1 load lands on next tenant's header slot → `0x1A00` green; larger loads read a 2-entry zero pad — the M-86 tell). Fix: `texInitPool` rounds the base up to 8 under `#ifdef PORT` (no-op on N64); 21/21 sweep PASS. Two defects: ① **visible green = misaligned texpool arena** (fixed as above). ② **CI texture-cache collision** (no palette-content key) — proven, **fix landed on branch `fix/d217-model-texture-palette` `f6fc0399`** (palette FNV-1a hash in the CI cache key), owes a 21-level `verify.sh sweep`; does not fix ①. |
 | **D174** | "No blood effect" — user reports no visible blood when shooting guards / into surfaces. | **User QA report; likely D120, unverified.** Decals: the D120 `PointUsage[]` converter fix (M-30) was never interactively verified and only takes effect after a full sidecar regen (`d43 && d69 && d88 --regen`) — check whether the playtest build had regenerated sidecars before concluding the fix failed. Spray: D172 observed the particle spray *drawing* (wrong color, magenta/cyan) on Silo — if the user sees no spray either, that's new info (different weapon/range, or the D172 decode is worse than "wrong color"). First step: BUNKER1 firefight with regenerated sidecars; if decals still absent, instrument the `chr.c:3328` decal walk. |