R-4 (round 17, 2026-07-28): which end is anchored FIRST.
"target" resolves arrival points before source departures,
so many-to-one flow spreads sources against the arrival
order rather than against the target's center. Default
"source" preserves existing scenes exactly.
R-4 (round 17, 2026-07-28): which end is anchored FIRST. "target" resolves arrival points before source departures, so many-to-one flow spreads sources against the arrival order rather than against the target's center. Default "source" preserves existing scenes exactly.