#87: mech armour PANELS now darken with damage -- the .DZM material system was loaded and unused

Players: "the actual enemy mech in external view is not showing darkened armor
panels".  We swapped destroyed LIMB meshes but never darkened a panel.

The 1995 game darkens armour through the MATERIALS.  MakeMechRenderables
(FUN_004cef28) built, per (damage zone, material), a watcher
FUN_004573e4(material, &zone->damageLevel, 0.1f) that snapshotted the materials

context/decomp-reference.md

@@ -474,6 +474,8 @@ default-ON (`'0'` disables).
 | `BT_POWER_DETACH_TEST=<name\|1>` | drop a subsystem's voltage link + force Auto, so the auto-hunt must recover it. `1` = first powered subsystem to tick; a NAME (`PPC_1`, `Myomers`) targets one, which is what proves FAILOVER to a different generator rather than a same-generator re-attach |
 | `BT_AUDIO_SOURCES=<n>` | request `n` OpenAL mono sources instead of the driver default (~256). **Opt-in on purpose** — the cap doubles as a governor, and with EFX reverb live a higher ceiling means more simultaneous voices mixing during heavy combat. Measure frame time. See [[wintesla-port]] |
 | `BT_SELF_DAMAGE_ZONE=<n>` | aim the BT_SELF_DAMAGE harness at an explicit zone (-1/unset = the lottery) -- ramps one zone deterministically past thresholds (#78 bench) |
+| `BT_ARMOR_LOG` | mech ARMOUR-DARKENING trace (#87): per-zone `.DZM` list -> draw-op binding counts at tree build, any `unmatched` material name, and every change of a bound zone's level with the resulting brightness |
+| `BT_ARMOR_FORCE=<0..1>` | pin EVERY bound armour zone to a fixed damage level, so the same scene can be rendered pristine and fully-damaged and diffed pixel-wise (`scratchpad/night7/armor_ab.sh`) |
 | `BT_DRIVE_LOG` | the demand-site drive scale: `[drive] n/drive/mm/dmd/mech` ~1Hz (drive = myomers speedEffect x gimp; mm = the gimp level via BTMechGimpLevel) |
 | `BT_GIMP_SPEED=<0..1>` | EXTRA gimp demand multiplier (default 1.0 = authentic since 2026-07-30: the real slowdown is the gimp gait machines' clamp to the wg clip speed — see [[locomotion]] §visible limp; the old 0.5 T3 stand-in is retired) |
 | `BT_PICK_LOG` | #73 aimed-pick diagnostics: `[segpick]` the segment→zone map at tree build (index, name, zone, sphere), `[pickwin]` the winning zone/score/t per pick (score ~0 = threading the part core, ~1 = envelope graze) |
@@ -497,6 +499,20 @@ recoil @4bc136-4bc19c (damage>3 → (0,0.6,−1.5) × damage/16; `gyroRumbleTime
 ex-"clipLoadGuard").  Byte tooling: `scratchpad/dis_4b2980.py` / `dis_range.py` over
 `reference/decomp/section_dump.txt`.
 
+**ARMOUR-DARKENING addresses** [T1] (#87; full story: [[rendering]]): `.DZM` res compiler
+`FUN_0041e4e0` (part_002.c:7341, reads the `material` key list per `[dz_*]` section); runtime
+consumer inside `BTL4VideoRenderer::MakeMechRenderables` **`FUN_004cef28`** (part_014.c:5190-5272);
+per-zone node ctor `FUN_00455c7c(...,0.04f)`; the per-material watcher
+**`FUN_004573e4(material, &zone->damageLevel, 0.1f)`** (part_007.c:9133, vtable `PTR_LAB_004f1730`,
+232 bytes) with Perform **`FUN_00457784`** (lerp constant `@0x4579a4` = 1.0; damaged factor
+`0x3dcccccd` = 0.1).  Material accessors: `dpl_GetMaterialAmbient` `FUN_0048baf4` /
+`Set` `FUN_0048ba98`, `Emissive` `FUN_0048bbb0`/`FUN_0048bb54`, `Diffuse` `FUN_0048bc6c`/
+`FUN_0048bc10`, `Specular`(4) `FUN_0048bd2c`/`FUN_0048bccc`, `Opacity` `FUN_0048bdf0` (READ ONLY --
+lerped but never pushed), flush `FUN_0048d4d4`; `dpl_SetMaterialRamp` `@0x48bfb0` (writes
+`material+0x1c`; ONE caller, load-time only).  Material lookup by name `FUN_00497678`.  The UNUSED
+sibling path: `dpl_Damagize` `FUN_004902b0` (tokens `{0x92,0x05,0x04}`), `SV_SPECIAL DAMAGE`
+dispatch @0x4599ae -- **zero shipped BGFs carry a DAMAGE token**.
+
 **PUNCH firmware decode** [T1] (the definitive mechanism, 2026-07-11): cmd 0x20 =
 vr_damage_action (VR_PROT.H enum); the i860 firmware content/VREND.MNG (code @0xf0400000)
 handler 'damageize' @0xf040f6f8 writes the token triple onto the geogroup's first THREE