---
id: open-questions
title: "Open Questions — deferred systems, unknowns, get-from-Nick"
status: living
source_sections: "CLAUDE.md §9; docs/HARD_PROBLEMS.md; per-subsystem deferral notes"
related_topics: [source-completeness, subsystems, multiplayer, combat-damage, locomotion]
---

# Open Questions

Known unknowns + deliberately-deferred systems. For each: what's known, what's missing, what
would resolve it, status. Deferred ≠ broken — most are marked-and-guarded stand-ins with the
authentic path scoped.

## From Nick (external — gating for some paths)
- **[GATING] The BT game SOURCE CODE** — the missing implementation `.cpp` (mech, subsystems,
  mapper, HUD, app; see [[source-completeness]]). Without it, Route A (recompile original) is
  impossible; we reconstruct from the binary instead. Likely on a backup/dev drive. Status: OPEN.
- Confirmation the PodPC image is the complete content master. (Low priority — the runtime
  `BTL4.RES` already has 8 maps + the full mech anim set.) Status: OPEN.
- Pod specifics for Phase 8: the 7-monitor driver setup, the RIO cockpit I/O protocol, current
  Win10+wrapper pod config. Status: OPEN.

## Deferred subsystems / feeds (authentic path scoped, marked in code)
- **0xBD3 SubsystemMessageManager (WAVE 8)** — a per-mech **damage/explosion consolidation hub**
  (`ConsolidateAndSendDamage` Performance @0049b784, `weaponExplosions` queue, `CommonDamageInformation`;
  messmgr.hpp). ctor `FUN_0049bca4` (vtable 0x50b954, installs a Performance → ticks). The factory
  caches it to **`Mech[0x10d]` = byte 0x434**. What wiring it needs: an untangle — our reconstruction
  MISLABELED `Mech[0x10d]` as `controlsMapper` and `mech4`'s live drive reads it as the mapper, so the
  real messmgr can't land there until the drive is re-pointed to the true mapper (**roster slot 0**,
  installed by `SetMappingSubsystem`/`MakeViewpointEntity`; a `MechRIOMapper`). Payoff = authentic
  damage/explosion consolidation (a COMBAT-fidelity improvement) + fixing the mapper/messmgr conflation.
  ⚠ **CORRECTION (verified 2026-07):** 0xBD3 does NOT gate the valve/Myomers/MessageBoard — those read a
  DIFFERENT object at **`mech+0x190`** (both `FUN_004ac9c8` the valve guard `→+0x274` and `FUN_004ad7d4`
  the Myomers gate `→+0x260` deref `owner+0x190`, which ≠ the 0x434 messmgr cache). The earlier
  "0xBD3 gates 4 things" note was wrong.
- **✅ `mech+0x190` IDENTIFIED (2026-07): it is the owning `BTPlayer`** (`Mech::GetPlayerLink()`,
  `MECH_OWNING_PLAYER`; ENTITY.h:430). Set by `FUN_0049f624` (the mech↔player bind: `mech+0x190 = player`
  AND `player->playerVehicle(+0x1fc) = mech`), which resolves the player from the mission player registry
  (`app+0x2c+0x54`, `FUN_0041fd18`) by the pilot key. The valve/Myomers "gates" read the owning player's
  fields at `player+0x260` and `player+0x274` (the reconstruction maps this block as `showDamageReceived@0x25c
  / showKills@0x260 / showDamageInflicted@0x264 / roleClassIndex@0x274` in btplayer.hpp — from the SCORING
  work, so the names may NOT match the gate semantics; the true meaning + the WRITER of `player+0x260/0x274`
  are not yet pinned — part_013.c:4553-4660 is the TorsoSimulation, a different object, not the setter). So
  there is NO new subsystem to build. **The wiring (small):** point `MechSubsystem::IsDamaged()` (`FUN_004ac9c8`, valve
  guard) at `GetPlayerLink()->`(0x274) and `Myomers::OwnerAdvancedDamage()` (`FUN_004ad7d4`) at
  `GetPlayerLink()->`(0x260) — via NAMED members (databinding trap: our BTPlayer layout ≠ binary; do NOT
  raw-read `player+0x260`). ⚠ Resolve first: (a) a naming conflict — `FUN_004ad7d4` is labeled BOTH
  `HeatModelActive` (heat.hpp) AND `OwnerAdvancedDamage` (myomers.cpp); re-verify which body is which; (b)
  the true semantic of `player+0x260/0x274` vs the scoring-derived `showKills`/`roleClassIndex` names. NOTE:
  these are MODE flags — in the basic test mission the inert Myomers / dormant valve is likely AUTHENTIC
  (advanced damage off); wiring makes them RESPOND when a mission enables the mode, not necessarily change
  the basic-mission behavior. The MessageBoard feed is separate (StatusMessagePool, below).
- **✅ Authentic target acquisition RECONSTRUCTED (tasks #36/#39, 2026-07-08)** — the `Reticle`
  pick-ray chain is LIVE (see [[combat-damage]] Targeting for the full port map): the crosshair =
  **torso boresight** (NO free-aim mouse — the pod stick twisted the torso; you steer to aim) →
  pick ray → per-frame lock (boresight ON the mech = locked; off = none) → aimed zone damage +
  designator hotbox; `BT_FIRE_ARC` is opt-in-only now. Firing needs a target but NOT a manual
  lock/pinpoint — the target is AUTO-acquired (task #40, binary-verified: FireWeapon doubly-gated
  on mech+0x388, but 0x388 has 11 reads / 0 direct stores across CODE → set indirectly). Residue:
  (a) the binary's own per-frame reticle→mech copy + the AUTO-TARGET SELECTOR are still in an
  un-exported gap (a message/selector; our port auto-targets the single living enemy — for MP,
  reconstruct the real multi-target selection: nearest/most-aligned/cycle); (b) our cockpit view is body-mounted, so on a
  TWIST-CAPABLE mech the crosshair should deflect with the torso twist (`BTTwistToReticleX` is
  wired for it) AND the torso should visibly lead the legs — verify on a twist mech when one is
  in play (the BLH is fixed-torso, boresight always centred); (c) pre-burial, the pick still
  tests the sinking wreck's collision box at its parked position (pre-existing wreck-targeting
  behavior).
- **Cockpit HUD leftovers (tasks #35-#38 residue, 2026-07-08)** — the reticle + 7 weapon pips +
  ALL the instrument dynamics are LIVE (the Execute @004cdcf0 gap was RECOVERED via capstone
  disasm, task #37; the authentic Lock producer + the simple-X mode landed in #38 — see
  [[gauges-hud]] for the full instrument map). Remaining: (a) the **blx_cop canopy shell**: it is
  the torso segment's SkeletonType_A mesh and fully encloses the eye; it renders as a black box
  because the skeleton-branch render path isn't giving it its texture + the PUNCH cutout (the
  canopy WINDOWS are punch texels — with punch live the black pane texels become holes and the
  world shows through the frame). Fix lives in the [[rendering]] skeleton/punch branch, not the
  HUD; hidden by name filter until then (`BT_INSIDE_COCKPIT=1` shows it). (b) the **3D marker
  chain** ([0x31c]/[0x320] dpl objects + the PNAME1-8.bgf player-name meshes over the locked
  target — matters for MP). (c) the compass rotation SIGN is derived-not-verified [T3] (turn
  left → the stem should swing right; flip the sin sign in Draw if footage disagrees).
- **StatusMessagePool (NULL stub, btstubs.cpp:62)** — the per-player status-message queue.
  BTPlayer+0x1dc is never populated → MessageBoard is empty (authentic for bring-up). What
  resolves it: wire the pool + decode `AddStatusMessage @0042e580` + the `Player__StatusMessage`
  record ({messageId@+0xc, nameEntity@+0x10}).
- **Gyroscope (0xBC4)** — layout + joint-I/O reconstructed, but the ctor field-init + the two
  integrators (IntegrateEyeJoint @004b2ec0 / IntegrateBody @004b30ec) are incomplete → writes NaN
  to the root joint. Reverted to a stub. A full subsystem-sim reconstruction (bigger than Torso).
- **MechControlsMapper look/eyepoint commit** — reconstructed but its offsets collide with declared
  members; arbitrate before enabling (no port consumer yet). The fire-trigger-through-mapper is
  still the `gBTWeaponTrigger` bring-up.
- **Weapon groups / per-button fire channels (decomp-anchored 2026-07-09)** — MechWeapon message
  handlers id 9 **`ConfigureMappables`** (`FUN_004b9550`) and id 10 **`ChooseButton`**
  (`FUN_004b95b8`), table @0x511860 region: ConfigureMappables binds the weapon's
  `fireImpulse`@0x31C to mapper fire-channel #N (msg value 1-based; <1 unbinds; mapper = roster
  slot 0, vtable +0x38 register / +0x3c unregister; weapon+0x110 = the bound-state), ChooseButton
  re-binds (vtable +0x44) — the pod's in-cockpit weapon→button GROUPING. Weapons sharing a button
  fire together; grouping was a PILOT choice (heat management: alpha vs split). The port's
  SPACE=all-energy / CTRL=missiles split is a stand-in default; the authentic system needs the
  mapper channel registration + who SENDS the default ConfigureMappables (mission/player setup —
  not yet traced). Payoff: authentic weapon groups + a path to chain-fire.
- **Myomers authentic coupling** — the structural un-stub is INERT (mover feed + heat-gen no-op).
  Real coupling needs the advanced-damage gate (`OwnerAdvancedDamage`/`FUN_004ad7d4` → the owning
  **BTPlayer** `mech+0x190`+0x260, NOT 0xBD3 — see the mech+0x190 item above) + `MoverAttach` routing
  into the LIVE JointedMover (must be reconciled with the gait cutover first).
- **SeekVoltageGraph** — 4 Seek* attrs unpublished (a cluster-child, not config-called; non-blocking).

## Locomotion / combat polish (non-gating)
- Authentic per-mech TURN-RATE constant (currently a bring-up constant rate).
- Body-callback gimp handlers (states 16-19, targets 0x70b2/0x7161 undecoded → fall back to stand);
  airborne callbacks (`FUN_004a6344`/`FUN_004a7970`).
- Wall-block-vs-climb tuning. **✅ Collision DAMAGE application — DONE 2026-07-08 [T2].** The two deferred
  dispatches in `Mech::ProcessCollision` (mech4.cpp: mech-vs-mech `:15324-15358` + icon-crunch `:15369-15401`)
  now fire: on a collision with another Mech or a CulturalIcon, an `Entity::TakeDamageMessage{zone==−1}` is
  dispatched to the victim (via `BTDispatchCollisionDamage`, the engine ctor — same as the weapon path), and
  STEP 6's cylinder table resolves the impact point → a zone on the receiver. Terrain (walls/hills) matches
  neither branch → blocks without damage (faithful). Reachability is guaranteed (`Mover::ProcessCollisionList`
  calls the **virtual** `ProcessCollision` → `Mech::ProcessCollision`); built + stable. The live dispatch
  wasn't captured headlessly (the solo auto-walker never rammed a tree/mech), but the path is proven reachable
  and composed of runtime-verified pieces. **Note:** validated STEP 6's height ref along the way —
  `collisionTemplate->maxY ≈ 7.1` (a real mech height), confirming `CylinderReferenceHeight` reads a height,
  not the heat value the `mech+0x2ec` dual-labeling (heat-gauge sink vs groundRef, mech4.cpp:2697) hinted at.
- **✅ Cylinder hit-location (STEP 6) — DONE + LIVE 2026-07-08 [T2].** Built + runtime-verified: the `dmgtable.cpp`
  classes now have real storage + a working `ResolveHit→zone`, the mech ctor loads the type-0x1d table by the
  DamageZoneStream name (`[cyl] table 'bhk1' layers=7`), and `Mech::TakeDamageMessageHandler` resolves
  unaimed (zone==−1) hits before base-routing. ⚠ The FIRST "verified" claim was PARTIAL: the table was
  cached via `Wword(0x111)` (the ABSORBER — stores nothing) so every unaimed hit silently no-op'd; fixed
  2026-07-08 by promoting the cache to the named member `Mech::damageLookupTable`
  ([[reconstruction-gotchas]] §2). Now verified end-to-end (19 zones resolving, `BT_AUTOFIRE` harness).
  Full change list in [[combat-damage]] "STEP 6 COMPLETE". Historical investigation notes retained
  below for provenance.
  **Re-investigated 2026-07 (see [[combat-damage]] for the full algorithm):** the table (height×angle
  grid, resource type 0x1d) IS built (recon `StandingAnimation` @Mech[0x111], but with an EMPTY name → 0 rows,
  because `ResourceFindByName` is a **no-op template stub**). **CORRECTION to the earlier note:** the LOOKUP is
  **exported** [T1] — `FUN_0049eb54` (table height→row) + `FUN_0049e678` (row angle→cell), NOT unexported.
  Only the thin `Mech::TakeDamageMessageHandler` glue (zone==-1 → call the lookup → `damageZones[zone]->TakeDamage`)
  is unexported, and it's fully implied by pieces already reconstructed → no disassembly needed. Remaining:
  6b real `FindByName` (name = the mech's type-0x14 DamageZoneStream name @ResourceDescription+0xc); 6c the 3
  container ctors + the lookup as a `BTCylinderResolveZone` bridge (ground the cell zone-dict stream format vs
  the real .RES bytes); 6d register the handler + verify. Feasible; the only open risk is the cell stream format.
  The earlier-cited `FUN_004a0230`/`FUN_0049ed0c` don't exist.
- **Death sequence — CORE DONE 2026-07-08 [T2]; effects+anim deferred.** `Mech::UpdateDeathState()`
  (mech4.cpp) reconstructs the death STATE machine (collapse `movementMode` → RP `VTV::DeathShutdown`
  subsystem loop → settle to disabled/frozen; wreck stays, no crash) — runtime-verified (`BT_DEATH_LOG`).
  Full map + citations in [[combat-damage]] "Death SEQUENCE". ✅ (b) `MechDeathHandler` DONE (mechdmg.cpp) +
  ✅ the render-side **RemakeEntity** destroyed-mesh swap DONE 2026-07-08 (btl4vid.cpp
  `RemakeEntityRenderables` + `BTRemakeMechModel` bridge; in-place `SetDrawObj` swap — the tree dtor does
  NOT cascade so never rebuild). ✅ (a) **RESOLVED — no collapse animation exists in BT 4.11** [T1]: the
  fall latch (modes 5-8 → table slots 0x1c-0x1f) is a vestige — no loader fills the slots, no fall clip
  ships, and firing it would bind resource 0 (an AUDIO stream) as keyframes. ✅ The authentic death
  VISUAL is the **WRECK-HULK SWAP** (death ModelList `blhdead` → effect 104 → the victim becomes its
  `<mech>dbr.bgf` burning hulk) — RECONSTRUCTED + verified (`SwapToWreck`, btl4vid.cpp; see
  [[combat-damage]] "Death SEQUENCE" for the full chain + proofs).
  ✅ The wreck **sinks** (the 1996 quadratic burial, `offsetY = -0.025·t²`, gone ~17s) with the `ldbr`
  debris field; at burial it goes **INERT** (collisionVolumeCount=0 + target lock dropped — no phantom
  blocking/hits). **Remaining**: (c) the whole-mech **DeathSplash** radius damage; wreck mesh FLAMES
  (flamesml/flamebig + sweep flicker, 1996 script case 4); the **full entity teardown at burial**
  (the authentic death-row removal — needs the mech render tree unhooked from the renderer first;
  the inert wreck is the safe stand-in until then).
  Do NOT issue DestroyEntityMessage on death (before the render-tree teardown lands).
- **Critical-subsystem plugs UNBOUND (43 skips/mech) [T3].** `MechCriticalSubsystem::subsystemPlug`
  never gets WIRED to its live subsystem (the ctor's Resolve() at mechdmg.cpp:276 only READS; the
  binding write is elsewhere/unreconstructed), so `SendSubsystemDamage` skips every entry via the
  unbound-plug guard (mechdmg.cpp, added 2026-07-08 after a live NULL-deref AV in
  `SendSubsystemDamage+0x93` — the 1995 binary derefs unchecked because there every plug is bound).
  Consequence: zone destruction does NOT yet propagate damage into carried subsystems (generator/
  gyro failures etc.). Also latent there: `SubProxy2` raw-offset reads (databinding trap) once s≠0.
- **Two dead Wword comparison branches (multiplayer)**: `mech.cpp:1511` + `:1613` (replicant
  leg-state/stability sync in ReadUpdateRecord) — always-false BTVal comparisons ([[reconstruction-gotchas]] §2);
  needs slots 0xf/0x10 promoted to named members when P6 replication work resumes.

## Multiplayer (Phase 7 / P6)
- Cross-pod COMBAT (target a replicant + route damage to the owning master).
- Replicant GAIT animation (replicants don't animate joints yet — derive from replicated velocity).
- The pod-LAN config (real IPs, bare-IP pilot entries). The WinSock2 TCP stack (L4NET.CPP) is
  reconstructed + smoke-tested on one box (two instances share a world, movement replicates).

## Rendering follow-ups (non-blocking)
- **.PFX effect-layer polish (deferred 2026-07-08; the layer itself is LIVE + verified).** The
  reconstructed BT particle layer (L4VIDEO.cpp, see its banner) renders the authentic .PFX content
  (fire + smoke, premultiplied blend, impact-frame oriented — weapon hits AND damage bands via
  `lastInflictingID`, now written by `Mech::TakeDamageMessageHandler`). Remaining nuances, all
  cosmetic: (a) `atten/attenv` distance attenuation not honoured; (b) the per-file texture name
  (`btfx:firesmoke1_scr_tex`) — all effects share the radial-masked grit sheet; decoding FIRE.BSL
  would give the authored sheet; (c) beams draw before particles, so a beam through thick smoke
  reads too bright (pass-ordering); (d) `colorWarp/alphaWarp` applied as `t^(1/warp)` [T4 convention];
  (e) emission uses rate×releasePeriod batching [T4 convention vs the exact 1995 emitter].
- Replacement-LOD selection for NON-additive multi-LOD models (needs the board's hot-spot/
  reference-point semantics; leads: `s_dplobject.lod_ranges[16]/lod_hot_spot`, 0x2047/0x2048).
- Day/night MATERIAL path priority (BMF/IMG) — infrastructure done, gated `BT_MATPRI` (over-applies
  to shared terrain mats); needs the terrain-material model understood.
- RGBA4444 alpha (TREE.BSL cutout) decoded but not alpha-tested outside punch batches; VTX/TGA paths.

## Content build sub-project (low priority)
- Lab/other-build maps (`des`/`burnt`/`frstrm`) are source-only (`.map` in CONTENT/BT/MAPS/); would
  need compiling into a RES via the DOS `btl4tool.exe`. The 8 RES maps cover testing.

## Key Relationships
- Feeds from: every subsystem/render topic (their deferral notes collect here).
- Gating master: [[source-completeness]] (the missing BT source).
