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KB: document the searchlight fog-swap latent bug (task #63, left as-is by decision)

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Investigation (workflow) found the searchlight-driven fog swap never worked in the
ORIGINAL 1995 binary either -- it's a latent bug, not a port regression:
SearchlightSimulation (@004b841c) reads requestedOn@0x1E0 (never written) while
ToggleLamp (@004b860c) toggles commandedOn@0x1DC; no bridge exists, so lightState
@0x1D8 is perpetually 0 (lamp never lights). The self-consistent sibling
ThermalSight reads the field it toggles (0x1DC) -- the tell. The port reproduces
the bug faithfully (searchlight.cpp:189). Additionally the port never constructs
PullFogRenderable, so even absent the bug the swap wouldn't fire.

Decision: LEAVE AS-IS + document (faithful to the buggy original); the port keeps
the static lights-ON fog= values. A working swap would DEVIATE from the shipped
binary (repair the sim to read commandedOn + construct PullFogRenderable at the
btl4vid MakeMechRenderables inside pass + a toggle input) -- fully scoped in the KB
if ever wanted. No code change this commit.

Documented in rendering.md (fog section), open-questions.md (deferred subsystems),
subsystems.md (Searchlight). Core per-map/time/weather fog (task #63) is unaffected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-13 22:04:29 -05:00
co-authored by Claude Opus 4.8
parent 225fa5951b
commit c0a0ec5e69
3 changed files with 39 additions and 9 deletions
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context/subsystems.md
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@@ -41,6 +41,11 @@ Making a base byte-exact GROWS every subclass — they must be re-based TOGETHER
- **WAVE 3** — power bus (Generator/PoweredSubsystem) + Emitter/PPC fire-path (end-to-end fire; heat
conducts to the central sink via the linked-sink roster).
- **WAVE 4** — standalone readouts: Sensor/Searchlight/ThermalSight/AmmoBin (de-shim, gate fixes).
- ⚠ **Searchlight has an ORIGINAL latent bug [T1, task #63]:** `SearchlightSimulation` (@004b841c)
reads `requestedOn`@0x1E0 (never written) while `ToggleLamp` (@004b860c) toggles `commandedOn`@0x1DC
— no bridge, so `lightState`@0x1D8 is perpetually 0 (lamp never lights). Present in the 1995 binary
(sibling ThermalSight reads the field it toggles, 0x1DC); the port reproduces it faithfully. Left
as-is by decision; it makes the searchlight→fog swap inert. See [[open-questions]] + [[rendering]] fog.
- **WAVE 5** — Torso (aim twist/elevation; joint-I/O reconstructed; the BLH record disables torso →
faithfully no visible twist).
- **WAVE 6** — Myomers (mover-coupled; structural un-stub is INERT — no live mover/heat coupling).