Destructible props LIVE: revive StateInstanceSwitchRenderable (Gitea issue #3)

Playtest report: trucks play a collision sound on impact but never change
state -- no explosion swap, no destroyed model, collision volume persists.

Investigation (BT_CULT_LOG census + BT_GOTO ram harness): the SIM was never
broken.  ARENA1 map-streams 124 CulturalIcon entities, each with a damage
zone, explosion resource and removeOnDeath; the mech crunch dispatch
(ProcessCollision -> BTDispatchCollisionDamage) reaches them; ~19 walking
bumps burn the zone -> CulturalIcon::TakeDamageMessageHandler spawns the
Explosion (psfx effect 1008 observed), posts the delayed BurningState and
deletes the collision boxes.  All of that ran correctly and invisibly.

The ACTUAL bug: the 2007 WinTesla port fully stubbed
StateInstanceSwitchRenderable ('STUBBED: DPL RB 1/14/07') -- ctor never
registered on the state dial, Execute never toggled anything -- so the
intact->rubble visual swap on BurningState NEVER fired, for every cultural
icon in the game.  The destroyed truck kept its intact model: exactly the
reported 'no state change'.

Revival (D3D9-native, 1995 semantics verbatim):
- StateInstanceSwitchRenderable now controls the draw COMPONENT via the
  SetDrawObj in-place drawable swap (the mech RemakeEntity mechanism):
  visible = captured d3d_OBJECT, hidden = NULL.  Initial state in the ctor,
  AddVideoWatcher on the SimulationState dial (SetState fires video
  watchers), toggle only on a real change.
- L4VIDEO cultural case passes the draw component + object (the dead
  dpl_INSTANCE param is gone); [video] Object hides at BurningState,
  Rubble shows.
- REQUIRED: cultural objects stay OUT of static-mesh consolidation
  (RecurseStaticObject, same exclusion class as banded LODs/shadows) --
  a merged static draws forever regardless of DrawObj.
- Permanent env diag BT_CULT_LOG: creation census (zones/explosion/flags/
  pos), TakeDamage trace, death transition, [cultvis] switch actions.

Verified live (BT_GOTO=-620,-328 ram, ARENA1): 19 crunches -> DYING ->
explosion 1008 at the icon -> [cultvis] HIDE x2 (intact) + SHOW (rubble)
-> contacts cease, mech walks into the former footprint.  Boot + render
un-regressed (statics consolidate as before minus the 124 icons).

KB: context/rendering.md new section (the full chain + the consolidation
gotcha).  MP replicant path shares the same SetState watcher (cross-pod
verification pending -- noted in the issue).

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

context/rendering.md

@@ -243,6 +243,28 @@ the user plays the DEBUG build, but the 10fps was NOT the debug build (RelWithDe
 split draw-vs-present + check the DEVICE flags before blaming the compiler. Diagnostics kept:
 `[spike]/[loadobj]/[rstat]`. [T2]
 
+## Cultural-icon (map prop) DESTRUCTION — revived 2026-07-19 (Gitea issue #3) [T2]
+Trucks/props/buildings are **CulturalIcon/Landmark** entities (`engine/MUNGA/cultural.h`, map-
+streamed via INTEREST.cpp; ARENA1 = 124 icons, each with a damage zone, `ExplosionModelFile`,
+`removeOnDeath`). The SIM was always complete [T0]: ram/weapon damage → `CulturalIcon::
+TakeDamageMessageHandler` → zone `damageLevel ≥ 1` → **Explosion entity** (Crunch variant for
+collision) + `WaitingToBurn` (+`timeDelay`) → `BurningState` + `UpdateCollisionVolumes` (boxes
+DELETED on `removeOnDeath`, else sunk by `destroyedYTranslation`). The mech-side crunch dispatch
+(`mech4.cpp ProcessCollision` → `BTDispatchCollisionDamage`, ×0.001 ram economy) reaches icons
+(≈19 walking-speed bumps kill the spawn-yard truck). What was BROKEN (the "no state change"
+report): the 2007 port fully stubbed **`StateInstanceSwitchRenderable`** ("STUBBED: DPL RB
+1/14/07") — the intact→rubble visual swap NEVER fired. Revived D3D9-native: the switch now
+controls the draw component via the **`SetDrawObj` in-place drawable swap** (the mech
+RemakeEntity mechanism); `[video] Object` hides at BurningState, `Rubble` shows; watcher =
+`StateIndicator::AddVideoWatcher` (SetState DOES fire video watchers). ⚠ REQUIRED gotcha:
+cultural objects must stay **OUT of static-mesh consolidation** (`RecurseStaticObject` — same
+exclusion class as banded LODs/shadows), else the merged mesh draws the intact model forever
+regardless of DrawObj. Explosion visual = the psfx route (effect 1008 observed). Verified live
+(BT_GOTO ram): HIDE×2 + SHOW(rubble), contacts cease, mech occupies the footprint. Diags:
+`BT_CULT_LOG` (census/damage/death + `[cultvis]`). MP: replicants transition via
+`ReadUpdateRecord` → same SetState watcher path (untested cross-pod).
+
 ## Key Relationships
 - Geometry/LOD: [[bgf-format]]. Base: [[wintesla-port]] (L4D3D). Shadow/visual-conform: [[locomotion]].
 - Renders on: [[pod-hardware]] (main 3D view).
+- Prop destruction feeds: [[combat-damage]] (crunch dispatch) · uses the psfx layer.