Another player's pod is moved between updates by dead reckoning, which
advances it toward the projected position by a fraction of the remaining
gap each step:
percent = time_slice / ((nextUpdate - lastPerformance) + time_slice)
That fraction is decided by nextUpdate, so predicting when the next
packet lands is not cosmetic - it sets how far every step moves. The
prediction was labelled HACK in the original source and deserved it: the
next gap was assumed to equal the previous gap. On a LAN the gaps were
all alike and it held. Over Steam a single late packet doubles the
expected gap, percent collapses, the pod barely advances for one step and
then catches up on the next - a visible tick.
Measured on a live connection, in the replicant's own step grid: 7 spikes
in 5 seconds, about 1.4 a second, matching the reported symptom, with
percent bottoming out at 0.014 against a normal range of 0.27 to 0.95.
Predict from the median of the last eight gaps instead. A median has a
breakdown point of half its samples, so one straggler - or three - moves
it not at all, while a genuine change in the send rate still carries it
within a few updates. Gaps that are non-positive (duplicate or reordered)
or multi-second (a join or a stall) never enter the window, and the
window is reset outright when the stream is interrupted.
Against the measured jitter pattern the blend fraction holds 0.282..0.286
where it previously swung 0.095..0.294 - a spread fifty times smaller.
This changes how remote pods MOVE, not merely how they are drawn, so it
feeds collisions with them as well. RP412NETPREDICT=0 restores the old
prediction for comparison on the same build, and the environ.ini entry
says to keep the setting alike on every machine in a race.
The RP412CAMLOG trace now also reports the interval being predicted and
the worst one-step-ahead miss, scored per entity rather than through the
file-scope statics the percent readings use - those are written by
whichever mover ran last, which is exactly the crossed frame of reference
this whole investigation kept tripping over.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
CydandClaude Opus 5
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