[Main Branch] Ballistic-Driven Accuracy, Kinematic Leading & Native Full-Auto…

[Skyki15]

This PR modernizes NPC combat in xray-monolith: deterministic hit resolution,
center-mass aiming, velocity-based leading, decoupled movement accuracy, and
native full-auto fire. All changes are applied on the main branch and build
successfully (Release | x64, engine-vs2022.sln).

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OVERALL GAMEPLAY SUMMARY

Before this PR, AI combat suffered from several stacked engine-level handicaps:

• RNG "ghost bullets" could ignore physically valid hits on the player
• NPCs hard-aimed at the player's head (instant headshot clustering)
• Shots aimed at where the target was, not where they would be when hit
• Running NPCs got massive artificial dispersion multipliers
• Full-auto weapons fired in stuttering 4–10 round bursts with forced pauses

After this PR:

• If a bullet hits your mesh, it deals damage — no RNG override
• NPCs default to upper-torso aim (bip01_spine1), tunable per NPC via LTX/DLTX
• All NPCs use full intercept prediction against moving targets
• NPC accuracy while moving matches their standing posture/scope dispersion
• Full-auto weapons fire continuously at native weapon fire_modes rate

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1. ABOLISH GHOST BULLET RNG
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FILE
xray-monolith\src\xrGame\Level_bullet_manager_firetrace.cpp

PROBLEM
When a bullet intersected the player actor's bounding sphere, the engine rolled
RNG against Actual Hit Probability (AHP) before running a real mesh collision
test. AHP combined difficulty settings, weapon hit_probability, shooter
hit_probability_factor, and distance falloff (hit_probability_max_dist).

If the roll failed, the bullet played a whine sound and passed through without
damage — a "ghost bullet" — even though the ray already intersected the player.
Stalkers/NPCs were unaffected; only the player actor went through this gate.

IMPLEMENTATION
Removed the entire AHP block (hpf/ahp calculations and Random.randF gate).
Actor hits now always run cform->_RayQuery() for physical mesh collision:
- Mesh hit → damage applies
- Bounding-sphere graze but mesh miss → whine sound, no damage (unchanged)

Left inert (optional follow-up cleanup):
Actor/CWeapon/specific_character hit_probability members and LTX values

GAMEPLAY CHANGE
AI shots that physically connect always register damage on the player.
Difficulty hit_probability_* and weapon hit_probability LTX values no longer
suppress valid hits. Whine sounds still play on near-misses that fail mesh test.

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2. MODERNIZED AIMING — CENTER-MASS DEFAULT & DLTX SUPPORT

FILES
xray-monolith\src\xrGame\sight_manager_target.cpp
xray-monolith\src\xrGame\ai\stalker\ai_stalker.cpp

PROBLEM
CSightManager::aim_target() fell back to bip01_head for player and living
stalker targets. Combined with dispersion, this caused frequent instant
headshots. Per-stalker aim_bone_id existed but was script-only — never loaded
from config by default.

On main branch, aim logic uses g_actor for player target detection.
MT branch additionally handles HUD first-person view (camera position when
player is in HUDview) via cast_actor()/cast_stalker().

IMPLEMENTATION
sight_manager_target.cpp:
- Fallback aim bone changed from bip01_head → bip01_spine1
- Main: uses g_actor for player; ::aim_target("bip01_spine1", ...) fallback
- MT: uses cast_actor()/cast_stalker(); HUDview → camera position

ai_stalker.cpp (CAI_Stalker::reload):
aim_bone_id(READ_IF_EXISTS(pSettings, r_string, section,
"default_aim_bone", "bip01_spine1"));

ai_stalker.cpp — global aim_target() (main uses LL_GetTransform bone matrix):
Shared bone lookup used by sight_manager and CAI_Stalker::aim_target()
MT branch uses LL_GetBoneWorldPosition API instead

DLTX / LTX example:
![m_stalker_monolith_experienced]
default_aim_bone = bip01_spine1

Per-NPC override: bip01_head for snipers, bip01_spine2 for lower torso, etc.
Scripts can still override via aim_bone_id() at runtime.

NOT CHANGED: LookAtActor net_Spawn callback still uses bip01_head (visual only).

GAMEPLAY CHANGE
NPCs default to upper-torso aim instead of head snapping.
Significantly reduces unrealistic headshot clustering.
Per-NPC aim bone tuning without recompiling.

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3. VELOCITY-BASED AIM LEADING (FULL INTERCEPT)

FILE
xray-monolith\src\xrGame\sight_manager_target.cpp

PROBLEM
SetFirePointLookAngles() computed yaw/pitch toward the target's current bone
position. No prediction for target movement or bullet travel time — NPCs always
shot at where you were, not where you would be when the bullet arrived.

IMPLEMENTATION
Added helpers in anonymous namespace (SetFirePointLookAngles combat path only):

get_object_velocity()
Physics velocity from actor/stalker via character_physics_support;
position-history fallback for other objects.

compute_lead_time()
Solves ballistic intercept: |r + v*t| = bullet_speed * t
Fallback: distance / bullet_speed when no valid quadratic root.

apply_velocity_leading()
Reads bullet_speed from active weapon LTX (fallback 1000 m/s).
Offsets aim point: target_pos += target_velocity * lead_time

Rank scaling was initially added then removed — all NPCs use full intercept
(lead_time multiplier = 1.0, no Rank() factor).

SetPointLookAngles() unchanged (non-combat look, no leading).

GAMEPLAY CHANGE
All NPCs lead moving targets at full strength regardless of rank.
Stationary targets unchanged (zero velocity → leading skipped).
Per-weapon bullet_speed from LTX drives lead calculation.
Moving players face significantly smarter AI gunfire.

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4. DECOUPLED WEAPON ACCURACY (MOVEMENT DISPERSION CLEANUP)

FILE
xray-monolith\src\xrGame\ai\stalker\ai_stalker_fire.cpp

PROBLEM
GetWeaponAccuracy() applied separate walk/run LTX multipliers when the NPC
was moving (path not completed). Example: disp_run_stand = 6.3 in m_stalker.ltx
could push dispersion 3–45× higher while running — causing visible intentional
misses at point-blank even when aim was on target.

IMPLEMENTATION
Removed the entire !path_completed() movement branch.

GetWeaponAccuracy() now always uses body-state dispersion:
stand + scope → m_disp_stand_stand_zoom
stand → m_disp_stand_stand
crouch + scope → m_disp_stand_crouch_zoom
crouch → m_disp_stand_crouch
fallback → m_disp_stand_stand

Unchanged: m_fRankDisperison, Lua _g.CAI_Stalker__GetWeaponAccuracy hook,
g_dispersion_base / g_dispersion_factor.

Inert LTX (no longer read for movement): disp_walk_stand, disp_walk_crouch,
disp_run_stand, disp_run_crouch.

GAMEPLAY CHANGE
NPCs no longer spray wildly just because they are walking or running.
Point-blank shots while moving are much more accurate.
Accuracy driven by rank dispersion, weapon, posture, and scope — not path state.

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5. NATIVE FULL-AUTO FIRE (WEAPON QUEUE MANAGEMENT)

FILE
xray-monolith\src\xrGame\WeaponMagazined.cpp

PROBLEM
NPC firing was artificially burst-limited:
1. CObjectHandlerPlanner::set_queue_params() set random queue sizes
(auto_min/max_queue_size_close = 4–10) with QueueWait pauses between bursts
2. Planner overrode weapon queue size after OnH_A_Chield attach
3. switch2_Fire() always set m_bFireSingleShot = true

Full-auto weapons fired in stuttering bursts instead of continuous fire.

IMPLEMENTATION
SetQueueSize(int size) — refactored:
fire_modes weapon, mode < 0 → WEAPON_ININITE_QUEUE (-1), full-auto
fire_modes weapon, mode > 0 → m_iQueueSize = mode (single/burst count)
No fire_modes, NPC parent → WEAPON_ININITE_QUEUE
No fire_modes, player → passed size unchanged (legacy)
Ignores planner/script burst overrides when fire mode applies

OnH_A_Chield():
Fire-mode weapons → SetQueueSize(GetCurrentFireMode()) for all parents
Non-fire-mode NPC weapons → WEAPON_ININITE_QUEUE

switch2_Fire():
m_bFireSingleShot = (m_iQueueSize >= 0)

Fire mode mapping (fire_modes LTX):
-1 → infinite queue, continuous auto
1 → single shot
2 → 2-round burst, etc.

GAMEPLAY CHANGE
NPCs with full-auto weapons fire continuously while engaging.
Burst/single modes still respected via weapon fire_modes LTX.
Eliminates engine-level stutter between artificial burst gaps.
Player weapon behavior unchanged.

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MT BRANCH BUILD FIXES (MT ONLY — NOT NEEDED ON MAIN)

During MT branch integration, sight_manager_target.cpp had a bad merge that caused
compile errors (missing braces, duplicate logic). Fixed on MT:

• Clean aim_target() block: MT cast_actor/HUDview/camera + bip01_spine1 fallback
• Restored global aim_target() in ai_stalker.cpp (LNK2001 unresolved external)
• Uses MT LL_GetBoneWorldPosition API

Main branch uses g_actor and existing LL_GetTransform aim_target(); no MT merge
fixes required.

Build verified: engine-vs2022.sln Rebuild Release|x64 — success (both branches).

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FILES MODIFIED (SUMMARY)

Level_bullet_manager_firetrace.cpp Ghost bullet RNG removed
sight_manager_target.cpp Center-mass aim, velocity leading, MT aim
ai_stalker.cpp default_aim_bone LTX, global aim_target()
ai_stalker_fire.cpp Movement dispersion removed
WeaponMagazined.cpp Native full-auto queue management

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OPTIONAL FOLLOW-UP CLEANUP (NOT IN SCOPE)

• Remove inert hit_probability infrastructure (Actor, Weapon, specific_character)
• Remove inert disp_walk_* / disp_run_* load from ai_stalker.cpp reload()
• Remove inert auto_queue_size effect documentation from stalker LTX guides