The user caught the inversion (blocked viewports, see-through frames); the
answer came from the rasterizer board itself: an i860 disassembly of the
VREND.MNG firmware decoded the damageize handler (@0xf040f6f8) -- cmd 0x20
(vr_damage_action) writes the dpl_Punchize token triple onto the punch
geogroup's first three geometry chunks IN FILE ORDER:
chunk1 = the detailed window-aperture shapes -> an invisible per-pixel MASK
chunk2 = the coarse hull -> the ONLY colour-drawn geometry (where not masked)
chunk3 = byte-identical hull twin -> the damage-reset record, never visible
Visible canopy = hull-minus-apertures. Both earlier readings were wrong ways
around the same three chunks: dropping all punch left floating fragments (no
hull); hiding the duplicate pair hid the HULL and drew the MASK -- the exact
inversion observed.
Port: bgfload tags per punch patch {non-paired pmesh = mask (role 1),
first twin = hull (role 2), second twin = skip}; L4D3D DrawMesh runs
mask->stencil-1 (no colour/z-write, z-tested), hull->stencil-NOTEQUAL,
mask->stencil-0; device D24X8 -> D24S8 + stencil clear. The cut never
touches z, so later-drawn entities show through the apertures.
BT_COP_PLATES=1 disables (diag).
In-game, all 8 mechs on pure defaults: connected dark frames with clear
viewports -- thor (the footage mech) shows the central viewport + surrounding
frame exactly as filmed. Combat regression clean (kill + no NaN).
Arena textured punch uses the same firmware kit; the black-texel alpha path
there is a working approximation, flagged in the KB.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
User report: the ground shadow painted OVER the mech's feet. Root cause: the
flat quad + big depth-bias (-0.004 ~= 2-4 world units) workaround for slope
burial -- a bias big enough to beat the TERRAIN also beat the FEET in the
depth test, and the shadow drew in the late alpha-blend pass (after the mech),
so z-arbitration was the only layering control.
Fix, four co-dependent parts (user-verified live: feet on top, opaque,
survives inclines/declines):
- TILT (mech.cpp UpdateShadowJoint): apply the SKL's own contract for
jointshadow ("apply terrain angle to pitch and roll") -- quad up aligned to
the surface normal via an orthonormal basis fed to the ENGINE's own
LinearMatrix->EulerAngles conversion. Hand-derived Euler signs are exactly
how the prior tilt attempts "dug into the hillside"; the engine conversion
is convention-proof. ~35 deg cliff-guard cap.
- SAMPLER (mech4.cpp): surface gradient from the collision probes PLUS
BTVisualGroundLift per probe -- the quad hugs the VISIBLE terrain, whose
lift varies across a slope; world->local rotation by the TRUE yaw from
localToWorld, not the drift-prone gDriveHeading mirror (the task-#48 bug
class). BT_SHADOW_LOG traces the normals.
- DRAW ORDER (new PASS_SHADOW, l4d3d.h/L4VIDRND/L4VIDEO): shadows draw
between the STATIC terrain and the DYNAMIC opaque bodies -- the classic
decal order. The mech, drawn after, z-passes over the shadow: the bias
can never paint the shadow over the feet, structurally.
- BIAS pairing (L4D3D.cpp): tilt on (default) -> decal epsilon -0.0008;
BT_SHADOW_TILT=0 flat fallback -> the old -0.004. BT_SHADOW_BIAS overrides.
KB (locomotion.md): the four-part arrangement recorded as co-dependent, with
the gait-desync-symptom diagnostic hint retained.
Co-Authored-By: Claude Fable 5 <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>
