Classify a flip-adjusted depth range[dMin, dMax] into a projection band.
VISIBLE band occupies [-below, 0) (below the cut, toward the floor).
OVERHEAD band occupies (0, +above] (above the cut, overhead).
An element overlapping both (e.g. a wall cut at mid-height) is 'spanning'
and drawn solid — its footprint is real near-floor geometry; the cut line
itself is emitted separately by the section cutter.
Classify a flip-adjusted depth range
[dMin, dMax]into a projection band.[-below, 0)(below the cut, toward the floor).(0, +above](above the cut, overhead).An element overlapping both (e.g. a wall cut at mid-height) is
'spanning'and drawn solid — its footprint is real near-floor geometry; the cut line itself is emitted separately by the section cutter.