Feature layer slot index in HexMap.featureData. Must be unique per map.
[tier 0=dense → tier 2=sparse][variant within tier]
OptionalallowedIf set, only cells whose terrain type index is in this list can host this scatter.
OptionaltiltRandom X/Z tilt applied to each instance matrix (radians). 0 = upright only.
OptionalplacementElevation band, shore, and river rules — see ScatterPlacementRules.
OptionalthresholdsOwn density curve; omit for the shared default. See ScatterThresholds.
Fully serializable description of a scatter layer. Embeds in a map save file. Does not hold Three.js objects — assets are referenced by stable string ID and resolved at load time via a registry.