The coarse motion threshold (15 px vs the 3 px still floor) followed the
per-frame "did the camera move" test directly. During a slow drag on a
janky main thread — the 66-model web session at 20 fps, mouse events
coalesced — some frames see no camera change, so the cull alternated
between thresholds every few frames: 84% of the visible set vanishing
and reappearing (139k <-> 22k objects in the log), with a full
visible-set re-upload at each flip feeding the very jank that caused the
gaps. On screen it read as the model sporadically jumping and returning
while orbiting slowly, easing as streaming and caching settled — which
is exactly how it was reported.
The motion state now latches: any camera movement arms it, and it only
drops after 250 ms of stillness, with the render loop kept alive over
the hold so the fine-threshold re-cull actually runs in an on-demand
loop. A drag degrades once at its start and restores once shortly after
it ends. Measured with a deliberately gappy scripted drag: two
transitions for the whole drag where each 120 ms pause previously
flipped it.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Dion Moult
ad113e1283