Variable: OnCollision3D

const OnCollision3D: Trait<{ onEnter: string; onExit: string; }>

Declarative collision/sensor reaction — the no-code path (B) on top of the Physics3DEvents manager (C). Put this on the SAME entity as a Collider3D (e.g. a trigger volume): when that collider begins/ends overlap with another, the physics system dispatches the named UIAction, passing the OTHER entity as ctx.target and { self, other, phase } in ctx.params.

REQUIRES a RigidBody3D on the same entity (or a rigidbody ancestor). A lone Collider3D with no body creates no Rapier collider and fires no events — for a static trigger volume use a RigidBody3D({ bodyType: 'static' }). (The physics system warns once about such an orphan collider.)

Works for both sensors (Collider3D.isSensor) and solid contacts. The dispatch is pipeline-safe (dispatchGameAction — never throws on a missing handler, and is 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 only to the other phase.

For richer reactions (arbitrary game state, filtering, cross-entity logic) skip this trait and subscribe to the physics3DEvents manager directly in code.

Variable: OnCollision3D ​

Variable: OnCollision3D