#87 dig closure: host response is linear (raw decomp re-read); the pixel curve was div-card firmware

Re-read the material damage watcher RAW (@004573e4 ctor / @00457784
change-push): 16 floats snapshotted, damaged = pristine x 0.1 (literal at
the MakeMechRenderables call site, watching zone+0x158), linear lerp, 13
floats written back, then FUN_0048d4d4 -- which is "flush_material": a dpl
command-stream marshal (opcode 100) to the i860 division card. The
material->ramp->texel response curve was CARD firmware and is not in
BTL4OPT.EXE; logged as an open question (ask: firmware/DIV docs/period
screenshots).

Field reconciliation, measured live: one 25-pt hit (ERLG class) snaps a
77-pt arm 0 -> 0.3247 in a frame -- "a single missile leaves visible
armor damage" holds under the linear curve for heavy hits; 2-pt ERS creep
(the leg-audit weapon) is the invisible case.

Bench additions: BT_WALK_ZONES=<name-list> walker filter (concentrated
per-region audits, scratchpad/night10/legwalk.sh) + BindArmourDamage
ORPHAN inventory under BT_ARMOR_LOG (proved every drawn op is
zone-claimed on the full tree).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

context/combat-damage.md

@@ -1044,12 +1044,24 @@ both sides).
 
 Render-path note (gotcha #23 discharged): the tint itself was pixel-proven with
 `BT_ARMOR_FORCE` A/B captures -- all-zones 1.0 renders the hull charcoal (0.1x
-floor), so "no discoloration" was never the renderer. Solo/master-side
-perception is the authentic ECONOMY: 2-25 pt laser events vs 68-185 pt zone
-pools = single-digit % levels = a 2-10% darkening + a doll tick of a few color
-indices. The cockpit doll maps all 28 zones (L4GAUGE.CFG:4788-4814 cmArmor
-lines -- feet + lower legs included); a "leg shots never show" report is those
-zones' levels peaking ~0.08-0.13, not a wiring gap.
+floor), forced 0.4 reads visibly grey at close range on a light skin, so "no
+discoloration" was never the renderer. Solo/master-side perception is the
+authentic ECONOMY: 2-25 pt laser events vs 68-185 pt zone pools. The eye
+catches SNAPS, not creep: a single heavy hit (ERLG large laser / missile
+class, amt=25) jumps a 77-pt arm 0 -> 0.3247 in one frame (measured live) =
+the pod veterans' "a single missile leaves visible armor damage"; 2-pt ERS
+fire creeps ~1.6%/hit and stays visually silent for a dozen hits (the
+"legs never show" reports -- their levels peak ~0.08-0.13). The cockpit doll
+maps all 28 zones (L4GAUGE.CFG:4788-4814 cmArmor lines -- feet + lower legs
+included); nothing is unwired (orphan audit 2026-08-03: every drawn op with a
+material name is claimed by a zone).
+
+Fidelity boundary [T1]: the HOST binary's response is LINEAR (watcher
+@004573e4/@00457784: 13 material floats lerped toward x0.1 by level, then
+"flush_material" to the division card). The CARD-side material->ramp->texel
+curve is i860 firmware absent from BTL4OPT.EXE -- see [[open-questions]]
+"i860 DIVISION-CARD firmware". If pod darkening was perceptually steeper at
+mid levels, that steepness lived there.
 
 ## The hit-location CYLINDER -- raw-bytes audit + chassis->table map (2026-08-02) [T1]
 

context/open-questions.md

@@ -22,6 +22,20 @@ authentic path scoped.
   further assets exist; the runtime `BTL4.RES` with 8 maps + full anim set is the master we have).
 - Pod specifics for Phase 8: the 7-monitor driver setup, the RIO cockpit I/O protocol, current
   Win10+wrapper pod config. Status: OPEN.
+- **The i860 DIVISION-CARD firmware / DIV render docs (the material→pixel response curve).**
+  Established 2026-08-03 (#87 dig): the HOST binary lerps 13 material colour floats linearly
+  toward ×0.1 by zone damageLevel (watcher @004573e4/@00457784, 0.1 literal at the
+  MakeMechRenderables call site) and then just **marshals the material to the card**
+  (`FUN_0048d4d4` = "flush_material", dpl command opcode 100 — siblings flush_ramp/flush_texture).
+  The card-side shading (how material colour selected/scaled the 256-row material ramps → final
+  texels) is i860 firmware, NOT in BTL4OPT.EXE — so the PERCEPTUAL damage-darkening curve of the
+  1995 pods cannot be recovered from this binary. Our port applies the host's linear factor at
+  draw (TFACTOR modulate, L4D3D). Field testimony ("a single missile leaves visible armor
+  damage") is arithmetically consistent with the linear curve — one 25-pt hit snaps a 68-90-pt
+  zone by 0.28-0.37 (measured live: amt=25 → rarm 0→0.3247) — but if the card's ramp mapping was
+  steeper than linear, mid-level creep damage read stronger on the pods than in the port.
+  ASK: div-card firmware image, DIV/dpl render docs, or period screenshots showing a
+  known-damage-level mech. Status: OPEN.
 - **Did the pod throttle quadrant have MECHANICAL detents** (how many / lever positions)? The
   software path is notch-free [T1, [[pod-hardware]]], but the gait SM's walk/run dead band
   ([[locomotion]]) only makes sense if the hardware discouraged parking the lever mid-band —