The byte-exact WORLD-ENTITY reconstruction (Projectile @4be1bc 0x340 / Missile @4bf5b4 0x368)
is infeasible on the 2007 engine: measured sizeof(engine Entity)=0x1BC vs the 1995 binary's
0x300, so the reconstruction's raw base-offset reads (velocity@0x1dc, roster@0x124, motion@0x250)
read GARBAGE on the engine (the Mech 0x638-vs-0x854 gap, but the entity integrator DEPENDS on
those offsets). So -- like the mech drive and the beam renderer -- flying projectiles are a PORT
reconstruction (BTPushProjectile/BTUpdateProjectiles in mech4.cpp, a static array + stack
messages, ZERO heap ops): seeded from the launcher's fire with the decomp's real muzzle
(GetMuzzlePoint) / launch speed (|launchVelocity|) / per-shot damage (damageData, split across
missileCount), they fly to the target (tracer via BTPushBeam) and deliver the weapon's damage on
impact through the SAME Entity::TakeDamage path as the beam (aim Mech::FirstVitalZone()).
THREE bring-up fixes were needed to make a projectile weapon fire at all (found by tracing):
1. TRIGGER: fireImpulse was only driven for the Emitter; ProjectileWeaponSimulation now sets
fireImpulse = gBTWeaponTrigger too (else CheckFireEdge never sees an edge).
2. AMMO BIN: OwnerSubsystemCount/OwnerSubsystem were stubbed ->0, so ammoBinLink never resolved
and ConsumeRound always failed; redirected to the real roster (owner->GetSubsystemCount()/
GetSubsystem(i) -- the AmmoBin 0xBCB constructs before the weapons 0xBCD/0xBD0).
3. JAM ROLL: UniformRandom() was stubbed `return 0.0f`, so CheckForJam's `0 < jamChance` ALWAYS
jammed (a projectile weapon could NEVER fire); replaced with a real LCG [0,1) (fires
~1-jamChance of the time -- authentic occasional jams).
Also: the mech's own target slot (owner+0x388) isn't populated in bring-up (the visible fire
targets the gEnemyMech global), so BTPushProjectile falls back to gEnemyMech.
Verified: Mad Cat PUSH=62 / IMPACT=31 (LRM missiles 3.33 dmg each split across the salvo + AFC100
autocannon 25 dmg), TARGET DESTROYED, 0 crashes, construction heapcheck-clean; BLH un-regressed
(also fires its ballistic weapon now). Diagnostics BT_PROJ_LOG ([projectile] PUSH/IMPACT).
REMAINING (deferred): the byte-exact world-entity Missile (Projectile : Mover, MP-replicable via
Registry::MakeEntity) -- the port projectile is master-local only (no MP replication); the real
per-weapon fire-rate/heat wiring off the subsystem sim (mech4 beam path is still the bring-up harness).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
