Combat: FIX weapon effectiveRange -- it degraded with heatLoad, not host-zone damage (task #50)

MechWeapon::UpdateTargeting computed effectiveRange = (1 - heatLoad) * weaponRange,
reading the weapon's own inherited HeatableSubsystem heatLoad. The authentic decomp
(@004b9bdc:6983) reads *(weapon+0xE0)+0x158 = Subsystem::damageZone->damageLevel --
i.e. effectiveRange = (1 - HOST-ZONE DAMAGE) * weaponRange. Same @0xE0-DamageZone-vs-
heat misattribution already corrected in HeatSink::UpdateCoolant (heat.cpp:803).

Impact: for a charge/discharge weapon (ER laser) the weapon's OWN heatLoad swings
0..1 every fire cycle, so effectiveRange collapsed toward 0 and the weapon was
perpetually "out of range" -> Emitter::FireWeapon's `if (dist <= effectiveRange)`
gate skipped SendDamageMessage -> NO damage submission and hence NO impact explosion.
The beam still rendered (beamFlag/beamEndpoint set before the gate), so the shot LOOKED
like a hit but did nothing -- the user-reported "lackluster/absent laser hits, esp.
the ER medium, on mechs AND buildings". PPCs mostly worked only because their heatLoad
happened to sit low/stable.

Fix: read the QUALIFIED this->Subsystem::damageZone->damageLevel (the MechSubsystem
shadow is a shim -- heat.cpp:812) so an UNDAMAGED weapon holds its full, STABLE
weaponRange, and range shortens only as the weapon's host zone takes battle damage.

Verified (parked in range of a building, autofire): laser effRange 500 STABLE
(was fluctuating 0/59/340/424 -> mostly out of range); impact explosions 13 in 22s
(11 laser id=16 + 2 PPC), up from ~2. Lasers now consistently damage + spawn FX.

Also adds env-gated diagnostics used to root-cause this: [fireW] range trace +
per-weapon explID (emitter.cpp), and BT_FIRE_AT_STRUCT (mech4.cpp) which designates
the nearest world structure so weapon-vs-structure fire can be tested without the
screen aim ray.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

context/combat-damage.md

@@ -61,6 +61,16 @@ Fixed-torso mechs (the BLH: `TorsoHorizontalEnabled=0` — no jointtorso in the
 boresight dead-ahead. Once locked, `Emitter::FireWeapon` converges with NO aim/arc test
 (part_013.c:7758). `MechWeapon::UpdateTargetState` (`FUN_004b9bdc` [T1]): `targetWithinRange =
 dist < (1 − hostZoneDamage) × weaponRange`. The 0x388 WRITER is in the same un-exported gap.
+⚠ **`hostZoneDamage` is `Subsystem::damageZone->damageLevel` (weapon `@0xE0 → +0x158`), NOT
+heatLoad** — the port originally computed `effectiveRange = (1 − heatLoad) × weaponRange`
+(mechweap.cpp), the SAME `@0xE0`-DamageZone-vs-heat misattribution corrected in
+`HeatSink::UpdateCoolant`. For a charge/discharge weapon (ER laser) the weapon's own `heatLoad`
+swings 0→1 every cycle, so `effectiveRange` collapsed to ~0 and the weapon was perpetually "out
+of range" → `SendDamageMessage` never ran → NO damage and NO impact explosion (the "lackluster/
+absent laser hits, esp. the ER medium, on mechs AND buildings" report). FIXED 2026-07-15: read
+the QUALIFIED `this->Subsystem::damageZone->damageLevel`; an undamaged weapon now holds full
+STABLE `weaponRange`. Verified: laser `effRange` 500 stable (was 0/59/340/424), impact explosions
+13/22s (was ~2). [T2] See [[reconstruction-gotchas]] (`@0xE0` shadow/heat class).
 **Port status: RECONSTRUCTED + runtime-verified (tasks #36/#39/#58) [T2].** The chain: the
 cockpit eye inherits the twist AUTHENTICALLY through the draw traversal (`Torso::PushTwist` →
 hinge `rotationAmount` → `HingeRenderable::Execute` multiplies the live hinge into the matrix

game/reconstructed/emitter.cpp

@@ -271,6 +271,15 @@ void
 	Scalar dist = (Scalar)Sqrt(delta.x*delta.x + delta.y*delta.y + delta.z*delta.z);	// FUN_004dd138
 	beamScale.z = dist / graphicLength;					// 0x434 (== beamScale[2]) = dist / 0x438
 
+	if (getenv("BT_FIRE_LOG"))
+	{
+		Entity *st = (owner != 0) ? *(Entity **)((char *)owner + 0x388) : 0;
+		DEBUG_STREAM << "[fireW] " << GetName() << " dist=" << (float)dist
+			<< " effRange=" << (float)effectiveRange
+			<< " inRange=" << (int)(dist <= effectiveRange)
+			<< " explID=" << (long)GetExplosionResourceID()
+			<< " tgt=" << (void *)st << "\n" << std::flush;
+	}
 	if (dist <= effectiveRange)							// this+0x328
 	{
 		// THE AUTHENTIC DAMAGE SUBMISSION (task #8; binary @004bace8:7758-7764):
@@ -349,6 +358,7 @@ void
 				<< " pct=" << (float)rechargeLevel
 				<< " tgt=" << (void *)((owner != 0)
 					? *(Entity **)((char *)owner + 0x388) : 0)
+				<< " explID=" << (long)GetExplosionResourceID()
 				<< std::endl;
 	}
 	targetWithinRange = UpdateTargeting();				// @004b9bdc -> this+0x34c

game/reconstructed/mech4.cpp

@@ -4502,6 +4502,43 @@ void
 			}
 		}
 
+		// DETERMINISTIC FIRE-AT-STRUCTURE TEST (BT_FIRE_AT_STRUCT, task #50 verify):
+		// the headless aim ray (BTGetAimRay) is flaky without a focused window, so
+		// this bypasses it -- designate the NEAREST world structure (360 sweep) as
+		// the target every frame so BT_AUTOFIRE can be tested against a real, stable,
+		// in-range building.  Diag only, off by default.
+		if (getenv("BT_FIRE_AT_STRUCT"))
+		{
+			extern Entity *gBTTerrainEntity;
+			Point3D eye = localOrigin.linearPosition; eye.y += 30.0f;
+			Point3D best; float bestR = 1e30f; bool got = false;
+			for (int a = 0; a < 24; ++a)
+			{
+				double th = (double)a * (6.2831853071795862 / 24.0);
+				Vector3D d((float)cos(th), 0.0f, (float)sin(th));
+				Point3D hp;
+				if (WorldStructurePick(eye, d, 2000.0f, &hp))
+				{
+					float dx = hp.x-eye.x, dz = hp.z-eye.z;
+					float r = (float)Sqrt(dx*dx + dz*dz);
+					if (r < bestR) { bestR = r; best = hp; got = true; }
+				}
+			}
+			if (got && gBTTerrainEntity != 0)
+			{
+				MECH_TARGET_ENTITY(this) = gBTTerrainEntity;
+				MECH_TARGET_SUBIDX(this) = -1;
+				MECH_TARGET_POS(this)    = best;
+				static float s_fas = 0.0f; s_fas += dt;
+				if (getenv("BT_FIRE_LOG") && s_fas >= 1.0f)
+				{
+					s_fas = 0.0f;
+					DEBUG_STREAM << "[fireat] nearest struct (" << best.x << ","
+						<< best.y << "," << best.z << ") r=" << bestR << "\n" << std::flush;
+				}
+			}
+		}
+
 		// HUD feeds: the range caret + the hotbox (world point + state) + the
 		// recovered-Execute instruments (compass, twist tape, group mask).
 		// The range caret tracks the PICK (authentic: :5639 computes it from

game/reconstructed/mechweap.cpp

@@ -500,8 +500,21 @@ Logical
 		rangeToTarget = (Scalar)Sqrt(				// FUN_004dd138
 			delta.x * delta.x + delta.y * delta.y + delta.z * delta.z);
 
-		// 1.0f == _DAT_004b9c98; heatLoad is the inherited HeatableSubsystem load.
+		// AUTHENTIC (decomp @004b9bdc:6983): effectiveRange = (1 - hostZoneDamage) *
-		effectiveRange = (1.0f - heatLoad) * weaponRange;	// *0x32c
+		// weaponRange, where hostZoneDamage is this weapon's OWN DamageZone.damageLevel
+		// (the QUALIFIED Subsystem::damageZone @0xE0 -> damageLevel +0x158), NOT
+		// heatLoad.  The old `heatLoad` read was the SAME @0xE0-vs-heat misattribution
+		// already corrected in HeatSink::UpdateCoolant (heat.cpp:803): for a charge/
+		// discharge weapon (ER laser) the weapon's OWN heatLoad swings 0..1 every cycle,
+		// so effectiveRange collapsed toward 0 and the weapon was perpetually "out of
+		// range" -- no damage submission, hence no impact explosion (user report:
+		// lackluster/absent laser hits on mechs AND buildings, esp. the ER medium).
+		// An UNDAMAGED weapon has damageLevel 0 -> full, STABLE weaponRange.  Use the
+		// QUALIFIED engine zone -- MechSubsystem::damageZone is a shim SHADOW (heat.cpp:812).
+		// 1.0f == _DAT_004b9c98.
+		::DamageZone *hostZone = this->Subsystem::damageZone;				// @0xE0
+		Scalar hostZoneDamage  = (hostZone != 0) ? hostZone->damageLevel : 0.0f;	// +0x158
+		effectiveRange = (1.0f - hostZoneDamage) * weaponRange;				// *0x32c
 
 		targetWithinRange = (effectiveRange > rangeToTarget) ? True : False;
 	}