Nav Mesh Registration & Generation

See also Navigation Data.

Note on IsNavigationRelevant

The virtual function UActorComponent::IsNavigationRelevant which is mostly known for its implementation in UPrimitiveComponent will by default return true if the primitive has the channels Pawn and Vehicle as blocked.

Registration process

When a primitive component is registered and bCanEverAffectNavigation is true as well as IsNavigationRelevant, FNavigationSystem::OnComponentRegistered is called. This will call UNavigationSystemV1::RegisterComponentToNavOctree, which checks that the component implements INavRelevantInterface and checks AActor::IsComponentRelevantForNavigation.

If the nav generation type is not static, the following happens: UNavigationSystemV1::RegisterNavRelevantObjectStatic is called which calls UNavigationObjectRepository::RegisterNavRelevantObject. This internal creates a new FNavigationElement instance (see UNavigationObjectRepository::RegisterNavRelevantObjectInternal and FNavigationElement::InitializeFromInterface).

FNavigationSystem::OnComponentUnregistered is called when the component unregistered (as well as some similar path that the register one).

Refreshing the nav data

In editor when you update a component collisions UActorComponent::DestroyPhysicsState will be eventually called. This will trigger a callback to UNavigationSystemV1::UpdateComponentInNavOctree which calls UNavigationObjectRepository::UpdateNavigationElementForUObject, this will find an existing FNavigationElement in UNavigationObjectRepository::RegisterNavRelevantObjectInterna and override it with a new “instance”.

Generation process

See also Static NavMesh Generation by Hussein Khalil.