The neighbour of level currentIdx worth making resident ahead of a switch,
or -1: the level across whichever of currentIdx's two boundaries lies
within a band of metric. Boundary b is the activation threshold of
level b (thresholds[b], between levels b − 1 and b); its band
half-width is fraction · min(gap below, gap above) — the gap above the
finest boundary is taken equal to the gap below — so the band is the same
share of a step at every level of a geometrically spaced ladder and, for
fraction ≤ 0.5, no two bands overlap. When the metric is inside the bands
of both boundaries (possible only for fraction > 0.5), the nearer wins.
This is the band the retired coverage cross-fade DREW both levels in; the
registry now only LOADS the neighbour there (LODGroupRegistry.preloadNeighbour).
Returns -1 for fraction <= 0, an out-of-range currentIdx or a
degenerate (zero-width) band. Allocation-free: it runs per group per frame.
The neighbour of level
currentIdxworth making resident ahead of a switch, or-1: the level across whichever ofcurrentIdx's two boundaries lies within a band ofmetric. Boundarybis the activation threshold of levelb(thresholds[b], between levelsb − 1andb); its band half-width isfraction · min(gap below, gap above)— the gap above the finest boundary is taken equal to the gap below — so the band is the same share of a step at every level of a geometrically spaced ladder and, forfraction ≤ 0.5, no two bands overlap. When the metric is inside the bands of both boundaries (possible only forfraction > 0.5), the nearer wins.This is the band the retired coverage cross-fade DREW both levels in; the registry now only LOADS the neighbour there (
LODGroupRegistry.preloadNeighbour). Returns-1forfraction <= 0, an out-of-rangecurrentIdxor a degenerate (zero-width) band. Allocation-free: it runs per group per frame.