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MP: FIX keyboard-driving peer skip -- non-pose records no longer kick the dead-reckon clock (task #50)

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The discriminating user report: peer motion was smooth under the autonomous
harness but skipped when driven by KEYBOARD -- even pure walking / pure spinning.
The harness pins throttle/turn constant; the keyboard SWEEPS the throttle lever
every frame of a key-hold (mech4 sLever integrator), so mapper->speedDemand
changes every frame, and the speed-deadband gate (authentic exact !=) fires a
type-2 speed record EVERY FRAME for the whole accel/decel.  The base reader
Simulation::ReadUpdateRecord stamps lastUpdate=Now() on EVERY record (flagged
'HACK - should be based upon message->timeStamp' in the 1995 source) -- so each
type-2 SHRINKS the peer reckoner's projection span (nextUpdate-lastUpdate)
without refreshing updateOrigin: the position target jumps backward toward the
stale origin, the next pose record yanks it forward -> target oscillation every
frame during any input sweep.  Matches the session-long 'worst on accel/decel'.

FIX (mech.cpp Mech::ReadUpdateRecord): non-pose records (2,3,5,6,7,8) preserve
lastUpdate around the base call (keeping the real payload, simulationState).
Pose (0) and resync (4) keep their authentic clock behavior.  BT_T2_CLOCK
restores the old stamping for A/B.

REPRO HARNESS (mechmppr.cpp): BT_FORCE_SWEEP=<period> triangle-sweeps the forced
throttle 0.2..0.9 -- a type-2 record per frame, the keyboard-skip repro the
constant-throttle harness could never produce.

Verified A/B, autonomous circle+sweep (the keyboard regime):
  old clock:  worst frame spike 10.4x avg, path/net ratio 1.069 (backtracking)
  guarded:    worst 4.6x, ratio 1.0022 (no backtracking)

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
arcattack
2026-07-14 19:12:52 -05:00
co-authored by Claude Opus 4.8
parent d78e77bf84
commit 93456be051
2 changed files with 120 additions and 6 deletions
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game/reconstructed/mechmppr.cpp
+18
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@@ -649,6 +649,24 @@ void
key_throttle = 0.08f; // near-idle half-cycle
}
}
// BT_FORCE_SWEEP=<period>: triangle-sweep the forced throttle 0.2..0.9
// continuously -- mimics a keyboard key-hold sweeping the lever every
// frame (a type-2 speed record per frame), the keyboard-skip repro.
{
static float s_swpP = -1.0f, s_swpClock = 0.0f;
if (s_swpP < 0.0f)
{
const char *fw = getenv("BT_FORCE_SWEEP");
s_swpP = fw ? (float)atof(fw) : 0.0f;
}
if (s_swpP > 0.0f)
{
s_swpClock += time_slice;
float ph = fmodf(s_swpClock, 2.0f * s_swpP) / s_swpP; // 0..2
float tri = (ph < 1.0f) ? ph : (2.0f - ph); // 0..1..0
key_throttle = 0.2f + 0.7f * tri;
}
}
// BT_FORCE_FLIP=<t>: invert the forced throttle after t sim-seconds
// (the mid-stride direction-change repro).
static float s_hFlip = -1.0f;