Slice 3 v1 (8898166) used SphereIntersectsCellBsp for the stickiness
check. User verification showed: ping-pong WAS closed (3 cell-transit
events vs 20+ pre-fix) but user still couldn't walk up out of cellar
because the stickiness was OVER-CORRECTED — the sphere still partially
overlapped the cellar cell at the top of stairs, so stickiness held the
player in the cellar even when the center had transitioned to the
cottage main floor cell.
Fix: switch the stickiness check from SphereIntersectsCellBsp (sphere
overlap) to PointInsideCellBsp (center-in). Matches FindCellList's
own semantics for "which cell are you in." Player stays in fallback
only while center is still inside fallback's BSP volume.
Trade-off:
- More permissive transitions (good — cellar-up works)
- Less aggressive stickiness, so some boundary ping-ponging may return
IF the sphere center oscillates across the boundary (rare; would
require sub-mm Z drift across the boundary line)
If the trade-off bites (ping-pong returns somewhere), the fix is a
small geometric margin around the point-in check — but verify before
adding.
Test suite: 1148 pass + 8 pre-existing fail (baseline maintained).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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