The boresight's non-mech pick only sampled the VISUAL heightfield (BTGroundRayHit),
which on arena1 is a single flat 'sky'-named ground mesh (and class-42 BuildTables
likewise holds only 'sky') -- so shots passed THROUGH the garages/walls and only mechs
moved the HUD range axis (user-reported regression: "buildings used to move the range
axis; now only mechs do, and you can only fire at a peer").
Real fix: the boresight now ALSO ray-tests the ZONE'S STATIC COLLISION SOLID TREE --
the same geometry that already blocks the mech's walk. Authentic engine mechanism:
Mover::FindBoxedSolidHitBy already tests the static world via
zone->GetCollisionRoot()->FindBoundingBoxHitBy(line). Factored its "static world" tail
into Mover::FindStaticSolidHitBy(Line*) (static solids only, no movers), wrapped by
Mech::WorldStructurePick(start,dir,range,&hit) (builds the world-space Line, reads the
entry point back via line->FindEnd since HitByBounded clips line->length=enter).
Boresight pick order is now: closest MECH (PickRayHit, damage zones + lock) -> closest
STRUCTURE (WorldStructurePick; occludes a mech BEHIND it; designates the gBTTerrainEntity
sentinel + entry point, so the range caret reads the structure distance and NO lock ring
draws, mech4.cpp:4529) -> flat ground (BTGroundRayHit) -> sky (fire-at-nothing). Also
un-skips arena1's misnamed-'sky' flat ground so the ground tier works (btvisgnd
geometry-aware skip + [mapent]/[rendent] census).
Verified headless: a BT_WSWEEP horizontal ray-fan on arena1 tracks position (3/24 hits
near the boundary -> 17-21/24 inside the interior garage cluster -> 3/24 past it =
DISCRETE interior solids, not an enclosing box), no crash/assert/AV. Interactive aim
(BTGetAimRay) can't run headless (no window -> noRay), so the sweep is the headless proof;
interactive aim is user-verified.
Note: FindBoundingBoxUnder (the ground/containedByNode BoundingBoxTree) is DOWNWARD-only
(gravity/ground-snap: *height = FindDistanceBelowBounded), useless for a horizontal
boresight; the static SOLID tree's FindBoundingBoxHitBy is the only ray-vs-world query.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Answers 'how did the original handle this?' from the decomp (subagent hunt):
the 1995 binary's replicant reckoner (FUN_004ab1c8 -> FUN_00409f58, part_000.c:9359)
integrates heading EXACTLY: build a unit axis-angle rotation quaternion from
angularVelocity*dt ({axis*sin(t/2), cos(t/2)}) and Hamilton-multiply it onto the
heading (FUN_00409d9c) -- exact for any timestep, stays on the unit sphere. It
further carries the full orientation quaternion in the FREQUENT pose record
(FUN_0040a938, 7-float pose), so the dead-reckon gap stays tiny.
Our reconstruction diverged two ways, both fixed:
1. ReconQuatIntegrate (mechrecon.hpp) -- the reconstruction of FUN_00409f58 -- was
STUBBED as , a crude small-angle VECTOR add. Restored to
the real exact axis-angle composition. (A 'no stand-ins' violation: the comment
even wrongly claimed Quaternion::Add == FUN_00409f58.)
2. The engine Mover reckoner (MOVER.cpp AcceleratedDeadReckoner/LinearDeadReckoner)
also did the vector Add on projectedOrigin.angularPosition -> over a long peer
record gap it diverged to ~180deg then snapped (the reported spin HANG/hesitation).
Routed both through a new ExactAngularProject() helper (same exact math).
3. Orientation only rode the sparse type-4 resync; during a PURE spin the linear
dense-send never fires (not translating), so the gap ballooned (~1.6s) and the now-
exact projection sat far ahead -> the slerp jumped. Added an ANGULAR dense-send
(resync every frame while |yawRate|>0.1), mirroring the original's frequent-
orientation model -> gap stays tiny -> smooth.
Verified live-autonomous (BT_AUTODRIVE+BT_FORCE_TURN + BT_RENDHDG render-rate probe):
the ~180deg divergence + multi-radian snaps are GONE (rendered maxStep 0.05-0.10 rad,
no jumps). User confirms: no frame hang/hesitation. MOVER.cpp change is strictly
more correct (exact==crude for the small per-frame master case; only large-gap peer
extrapolation changes), so walking is unaffected.
KNOWN REMAINING (separate, smaller): the turn-STEP leg animation (trn clip, mech2.cpp
advance_normally) runs at a FIXED idleStrideScale cadence that does not scale with the
rotation rate, so the legs lag/skip vs the (now-correct) body rotation. Next.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Clean, self-contained extraction of the BattleTech-specific work from the
reverse-engineering workspace -- engine + game + content + build, with nothing
from Red Planet or the raw archive dumps. Builds green (Win32) and runs the
single-player drive->animate->target->fire->damage->destroy loop out of the box.
Layout:
engine/ MUNGA + MUNGA_L4 shared 2007 engine, carrying our BT render/loader
work (bgfload/L4D3D/L4VIDEO: BSL bit-slice decode, LOD/ground/shadow
models) + image codec; the minimal rp/ headers the audio HAL needs
game/ reconstructed BT logic + surviving-original BT source + fwd shims
+ WinMain launcher
content/ full runtime tree (BTL4.RES, VIDEO/, GAUGE/, AUDIO/, eggs, BTDPL.INI)
docs/ format specs + reconstruction ledgers
reference/ raw Ghidra pseudocode (recon source-of-truth) + decomp exporter
tools/ MP console emulator + map/resource scanners
One top-level CMake builds munga_engine lib + bt410_l4 game lib + btl4.exe.
All paths relativized (186 fwd shims + ~437 CMake abs paths -> repo-relative);
DXSDK is the one external, overridable via -DDXSDK. Verified: builds to a
byte-identical 2.27MB exe and runs combat (TARGET DESTROYED, 0 crashes) against
the bundled content.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
