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aimed fire strikes the part under the crosshair: the per-segment pick (#73)

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The port's target pick was a whole-mech bounding-box slab test, and every hit
-- aimed or not -- dispatched zone -1 into the victim's cylinder lottery. The
recovered 1995 model (the division-card scene intersection) struck a SEGMENT
and credited that segment's own damage zone. This is the port's equivalent.

At render-tree build, each segment's draw object and its PrimaryDamageZone --
authored per segment in the skeleton stream, read by JMOVER.cpp:290 -- are
recorded in MechRenderTree::segPick. The pick (BTL4VideoRenderer::
MechSegmentPick) ray-tests the per-segment bounding spheres on the live posed
skeleton, using the draw-cached mLocalToWorld (at most one frame stale, fine
for aiming).

Selection is SPECIFICITY-FIRST: among the spheres the ray pierces, the
smallest radius wins, normalized-distance tie-break. Both obvious rules were
measured failing the same way before this one: the torso mesh's sphere
(r~4.1 on the MadCat, vs shoulders at r~1.0) envelops nearly the whole mech,
so its front face is nearest for any aim AND any near-body ray normalizes to
~0 against it. Limb spheres nest inside the envelope; smallest-pierced picks
the most specific part on the aim line, and the torso wins only when no limb
is threaded -- the per-part semantic the pod's mesh test produced.

mech4.cpp tries the segment pick per candidate; the box PickRayHit survives
only as the fallback (no tree yet, wrecked, spectator), still carrying zone
-1 into the lottery, and a structure occlusion clears the zone. The winner's
zone rides MECH_TARGET_SUBIDX + targetReticle.targetDamageZone into
SendDamageMessage, so aimed hits now dispatch a real zone; the victim's
handler applies it directly (bursts 2+ still re-lottery, authentic per the
recovered @0x4a0230 loop).

Bench, the same L/C/R sweep that exposed the bug: aiming left now lands
36/41 hits on zone 2 = jointlshoulder -- the left arm -- with a 0.30 thread
score, where the same aim was a 6-way lottery spray before. The MadCat's
authored segment->zone map is rich (shoulders 2/9, guns 6/17, hip 1, six leg
zones, torso 0). Known approximations, flagged for field verification:
sphere bounds rather than triangles, and a torso-envelope graze credits the
torso where the pod's exact mesh test would have missed into air.

The field protocol is the one the testers already ran on night 6: stationary
mechs, short range, fire only at one arm -- the paper doll should now damage
THAT arm.

Diag: BT_PICK_LOG ([segpick] map at build, [pickwin] per pick).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
This commit is contained in:
Joe DiPrima
2026-07-29 13:04:11 -05:00
co-authored by Claude Fable 5
parent e110b10ac8
commit 8a99972f22
5 changed files with 205 additions and 10 deletions
Download Patch File Download Diff File Expand all files Collapse all files
game/reconstructed/mech4.cpp
+32 -5
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@@ -4796,6 +4796,7 @@ void
// CODE -- written indirectly, never a manual player lock).
Entity *hotTarget = 0; // the enemy mech under the boresight
Point3D hotPoint; // picked world point on its hull
int hotZone = -1; // #73: the struck SEGMENT's zone (-1 = box fallback -> lottery)
Entity *pickTarget = 0; // what the boresight ray hit (mech/terrain)
Point3D pickPoint; // where it hit
// BT_RANGE_LOG (Gitea #4 VERDICT instrumentation -- uncommitted diag):
@@ -4973,13 +4974,33 @@ void
// pick the CLOSEST one the boresight ray strikes -- generalising
// the solo gEnemyMech.
float bestDist = 1e30f;
hotZone = -1; // #73: reset per frame (declared with hotTarget)
for (int ci = 0; ci < nc; ++ci)
{
Mech *m = (Mech *)cand[ci];
if (m == 0 || m->IsMechDestroyed())
continue;
// #73 -- PER-PART pick first. The 1995 pick was a dpl scene
// intersection against the DRAWN geometry (the division card
// cast from the view; results at DCS/segment granularity), so
// aimed fire struck a SEGMENT and credited that segment's own
// damage zone. The renderer-side equivalent ray-tests the
// per-segment bounding spheres on the live posed skeleton and
// returns the nearest segment's hit point + PrimaryDamageZone.
// The whole-mech box (PickRayHit) survives only as the
// fallback when no tree/segment resolves -- its zone stays -1,
// which routes through the unaimed cylinder lottery as before.
extern int BTMechSegmentPick(void *mech, const float s[3],
const float dir[3], float max_range,
float hit_out[3], int *zone_out);
Point3D hp;
if (!m->PickRayHit(rayStart, rayDir, 4000.0f, &hp))
int zone = -1;
float segHit[3];
if (BTMechSegmentPick(m, rs, rd, 4000.0f, segHit, &zone))
{
hp.x = segHit[0]; hp.y = segHit[1]; hp.z = segHit[2];
}
else if (!m->PickRayHit(rayStart, rayDir, 4000.0f, &hp))
continue;
float dx = hp.x - rs[0], dy = hp.y - rs[1], dz = hp.z - rs[2];
float d = dx*dx + dy*dy + dz*dz;
@@ -4988,6 +5009,7 @@ void
bestDist = d;
hotTarget = cand[ci];
hotPoint = hp;
hotZone = zone;
}
}
// WORLD-STRUCTURE pick (task #50): ray-test the STATIC collision
@@ -5054,6 +5076,7 @@ void
// HudSim part_013.c:5620).
pickTarget = (structOwner != 0) ? structOwner : gBTTerrainEntity;
pickPoint = structPoint;
hotZone = -1; // #73: a structure has no mech zone
rlPickClass = 2; // BT_RANGE_LOG (issue #4)
++gAimGround;
}
@@ -5078,12 +5101,16 @@ void
}
// The Reticle struct (the mech's TargetReticle attribute): position,
// pick result. targetDamageZone stays -1 -- the zone ROLL happens at
// damage delivery (the authentic percent-table roll, STEP 6).
// pick result. #73: targetDamageZone now carries the struck
// SEGMENT's zone from the per-part pick -- the authentic aimed-fire
// model ("For BattleTech, damage zones are only valid via reticle
// based weapons", ENTITY3.h:131). It stays -1 only on the box
// fallback, which routes through the unaimed cylinder lottery
// (STEP 6) exactly as before.
targetReticle.reticlePosition.x = gBTAimX;
targetReticle.reticlePosition.y = gBTAimY;
targetReticle.targetEntity = pickTarget;
targetReticle.targetDamageZone = -1;
targetReticle.targetDamageZone = (pickTarget != 0) ? hotZone : -1;
if (pickTarget != 0)
targetReticle.rayIntersection = pickPoint;
@@ -5091,7 +5118,7 @@ void
if (pickTarget != 0)
{
MECH_TARGET_ENTITY(this) = pickTarget;
MECH_TARGET_SUBIDX(this) = -1;
MECH_TARGET_SUBIDX(this) = hotZone; // #73: aimed zone (or -1)
MECH_TARGET_POS(this) = pickPoint; // beam endpoint = the pick
}
else if (gBTTerrainEntity != 0)