AI Perception Types

UAIPerceptionSystem

About

AI Subsystem managing AI Perception through registered AI Senses between Listeners and Stimuli Sources.

Created in UAISystem::PostInitProperties.

Inside UAIPerceptionSystem::Tick it calls UAISense::Tick for each Senses. This function calls UAISense::Update, which does something different depending on the sense behavior.

Senses management

This subsystem holds a list of Senses.

Sense registration

UAIPerceptionSystem::RegisterSenseClass is the function which updates the Senses array. This function is only called in UAIPerceptionComponent::RegisterSenseConfig and UAIPerceptionSystem::RegisterSourceForSenseClass (in case a UAIPerceptionStimuliSourceComponent registers with a sense class that wasn’t registered yet).

Stimuli source registration

UAIPerceptionStimuliSourceComponent registers themselves as source of stimuli via UAIPerceptionSystem::RegisterSourceForSenseClass which calls UAIPerceptionSystem::RegisterSource. This adds a unique FAISenseID with it’s SourceActor in a temporary array called SourcesToRegister (entry is of type FPerceptionSourceRegistration).

This array is iterated in UAIPerceptionSystem::Tick via UAIPerceptionSystem::PerformSourceRegistration. If the source actor is still valid and the sense class was already previously registered and added to the Senses array this will call UAISense::RegisterSource as well as create a new FPerceptionStimuliSource entry in the RegisteredStimuliSources array.

Listener Containers

ListenerContainer invalid entries are remove if necessary in UAIPerceptionSystem::Tick and UAIPerceptionSystem::UnregisterListener. Entries are added in UAIPerceptionSystem::UpdateListener if new. See usages of UAIPerceptionSystem::OnNewListener, UAIPerceptionSystem::OnListenerUpdate and UAIPerceptionSystem::OnListenerRemoved.

Components

UAIPerceptionComponent

About

Placed on AI Controller. AIPerceptionComponent is used to register as stimuli listener in AIPerceptionSystem and gathers registered stimuli. UpdatePerception is called when component gets new stimuli (batched).

StimuliToProcess is updated via UAIPerceptionComponent::RegisterStimulus

Available delegates

• OnPerceptionUpdated: Called in UAIPerceptionComponent::ProcessStimuli with an array of all the actors which were the source of the stimuli.
• OnTargetPerceptionForgotten: this is only called if bForgetStaleActors in Project Settings is true. The param is the actor we forgot.
• OnTargetPerceptionUpdated: Notifies all bound objects that perception info has been updated for a given target. The notification is broadcast for any received stimulus or on change of state according to the stimulus configuration. This delegate will not be called if source actor is no longer valid * by the time a stimulus gets processed.
• OnTargetPerceptionInfoUpdated: Notifies all bound objects that perception info has been updated for a given target. The notification is broadcast for any received stimulus or on change of state according to the stimulus configuration. This delegate will not be called if source actor is no longer valid * by the time a stimulus gets processed. This delegate will be called even if source actor is no longer valid * by the time a stimulus gets processed so it is better to use source id for bookkeeping.

Forgotten Actors

OnTargetPerceptionForgotten is called from either UAIPerceptionComponent::ForgetActor or UAIPerceptionComponent::ForgetAll.

ForgetAll is called in UAIPerceptionComponent::CleanUp. ForgetActor is called in UAIPerceptionComponent::ProcessStimuli using the local ActorsToForget array, which is filled while iterating StimuliToProcess if FAIStimulus::WasSuccessfullySensed is false, FAIStimulus::IsExpired is true and bForgetStaleActors is true.

UAIPerceptionStimuliSourceComponent

Gives owning actor a way to auto-register as perception system’s sense stimuli source. To register the owner actor with the given senses, you must have bAutoRegisterAsSource enabled or manually call RegisterWithPerceptionSystem.

RegisterWithPerceptionSystem will get the unique UAIPerceptionSystem for the world through UAISystem (see UAIPerceptionSystem::GetCurrent). Then for each senses in the array it will call UAIPerceptionSystem::RegisterSourceForSenseClass.

UPawnSensingComponent

Deprecated since 5.5.

Interfaces

IAIPerceptionListenerInterface

Senses

Senses - Base

See UAIPerceptionSystem for more information on how they are used.

FAISenseID

Typedef of FAINamedID<FAISenseCounter>.

UAISenseConfig

The config uses GetSenseImplementation to get the class of the AI Sense.

UAISense

Base class of all sense classes.

Available delegates:

• OnNewListenerDelegate: Called when a new FPerceptionListener registers with AIPerceptionSystem.
• OnListenerUpdateDelegate: Called when a registered FPerceptionListener changes.
• OnListenerRemovedDelegate: Called when a FPerceptionListener is removed from AIPerceptionSystem.

UAISenseEvent

Senses - Sight

UAISense_Sight

Inside UAISense_Sight::Update, UAISense_Sight::ComputeVisibility is called, which calls FAISystem::CheckIsTargetInSightCone.

IAISightTargetInterface

FAISightQuery

Senses - Blueprint

UAISense_Blueprint

Senses - Damage

UAISense_Damage

Senses - Hearing

UAISense_Hearing

Senses - Prediction

UAISense_Prediction

Senses - Team

UAISense_Team

Senses - Touch

UAISense_Touch

Stimuli

FStimulusToProcess

FAIStimulus

bSuccessfullySensed is true if the sight query was successful. This means it will be false if the target actor leaves the sight cone.

For example for UAISense_Sight different values are given to the FAIStimulus constructor. See UAISense_Sight::UpdateQueryVisibilityStatus and UAISense_Sight::UnregisterSource.

Miscs

FPerceptionSourceRegistration

FPerceptionStimuliSource

FPerceptionChannelAllowList

FPerceptionListener

Should contain only cached information common to all senses. Sense-specific data needs to be stored by senses themselves.

It holds a weak ref to an UAIPerceptionComponent.

FActorPerceptionInfo

FActorPerceptionUpdateInfo