@modoki/engine / index / OnZone3D
Variable: OnZone3D
constOnZone3D:Trait<{onEnter:string;onExit:string; }>
Declarative Zone3D trigger reaction — the no-code path on top of the Zone3DEvents manager. Put this on the SAME entity as a Zone3D: when a ZoneOccupant entity enters or leaves the zone volume, the zone-trigger system dispatches the named UIAction, passing the OTHER (occupant) entity as ctx.target and { self, other, phase } in ctx.params.
A zone is a PURE geometric containment test — NO physics colliders or RigidBody3D needed. It fires for any entity tagged ZoneOccupant whose world position is inside the Zone3D volume (position = centre; scale → volume by Zone3D.shape). The dispatch is pipeline-safe (dispatchGameAction — never throws on a missing handler, inert unless the sim is running), so an unwired action name is a warning, not a frame-aborting crash. Leave a field empty to react to only the other phase.
For richer reactions (arbitrary game state, filtering, cross-entity logic) skip this trait and subscribe to the zone3DEvents manager directly in code.