Interaction system

The interaction system is implemented in the PulseAbility module and centered around:

• UPulseInteractAbility
• UPulseAbilityTask_QueryInteractables
• UPulseAbilityTask_ManageInteractables
• IPulseInteractableInterface
• UPulseInteractableComponent

Main runtime flow

At runtime, UPulseInteractAbility does the following:

1. Activates locally and starts query/manage tasks (BeginQueryInteractables).
2. Query task detects focused interactables (sphere/component overlap or trace).
3. Manage task keeps a list of focused interactables and selects one by priority.
4. Ability exposes focus/selection/interaction events.
5. StartInteraction() and EndInteraction() call interface events on the selected target.

Core methods in UPulseInteractAbility:

• ActivateAbility(...)
• BeginQueryInteractables()
• NewInteractableFocused(...)
• InteractableFocusLost(...)
• InteractableSelected(...)
• StartInteraction()
• EndInteraction()

Query modes

EPulseInteractQueryType supports three query strategies:

1. BySphere
2. ByComponent
3. ByTrace

BySphere

• Creates a transient USphereComponent on the interactor actor.
• Uses overlap begin/end events to add/remove interactables.
• Uses SphereQueryRadius and SphereQueryCollisionSettings.

ByComponent

• Uses existing primitive components on the interactor.
• Components are discovered by tag:
  • Pulse.Ability.Interact.InteractableComponent
• Components must generate overlaps.

ByTrace

• Performs periodic trace queries using FPulseTraceParams.
• Supports sync and async trace (bAsyncTrace).
• Start/end is provided by a trace location provider (UPulseTraceLocationProvider).

Supported provider classes include:

• UPulseTraceLocationProvider_Default
• UPulseTraceLocationProvider_Pawn
• UPulseTraceLocationProvider_Camera
• UPulseInteractTraceLocationProvider_BP

Focus, selection, and interaction semantics

Focused interactables

Query task stores currently focused actors/components and emits:

• OnInteractableFound / OnInteractableLost interface callbacks
• ability-side notifications (NewInteractableFocused, InteractableFocusLost)

Selected interactable

Manage task sorts focused interactables by prioritizer result and selects the highest one.

• Old selected receives OnInteractableUnselected
• New selected receives OnInteractableSelected

Interaction

StartInteraction():

• Checks selected target.
• Validates CanBeInteractedWith.
• Sets InteractingActor / InteractingComponent.
• Calls OnInteractionStarted.

EndInteraction():

• Calls OnInteractionEnded.
• Clears interacting references.

GetInteractionTime() returns elapsed seconds while actively interacting.

Interactable interface contract

IPulseInteractableInterface defines:

• availability checks:
  • CanBeFocused
  • CanBeInteractedWith
• lifecycle callbacks:
  • OnInteractableFound
  • OnInteractableLost
  • OnInteractableSelected
  • OnInteractableUnselected
  • OnInteractionStarted
  • OnInteractionEnded
• priority/replication hooks:
  • GetInteractablePriority
  • ShouldReplicateInteraction

Important behavior:

1. If actor implements the interface, actor-level interaction takes precedence.
2. If only components implement it, component selection logic is applied.

Component selection for multi-component actors

When an actor has multiple interactable components, the ability resolves one active component using:

• Blueprint override GetInteractableComponentToFocus_BP(...), or
• UPulseInteractComponentSelector instance, or
• fallback to first component

Built-in selectors:

• UPulseInteractComponentSelector_Priority
• UPulseInteractComponentSelector_Closest

Component changes while focused trigger:

• ability callback InteractableComponentChanged(...)
• old component OnInteractableLost
• new component OnInteractableFound

Prioritization

Selection priority is handled by UPulseInteractPrioritizer.

Built-in options:

1. UPulseInteractPrioritizer_Default (uses GetInteractablePriority)
2. UPulseInteractPrioritizer_Closest (distance-based with optional look-at bonus)
3. Blueprint extension via UPulseInteractPrioritizer_BP and UPulseInteractPrioritizer_Closest_BP

Gameplay tags and events

Declared in PulseInteractAbility.cpp / PulseInteractAbility.h:

• Focus:
  • Pulse.Gameplay.Event.Interact.Focus.Gained
  • Pulse.Gameplay.Event.Interact.Focus.Lost
• Selection:
  • Pulse.Gameplay.Event.Interact.Selected
• Interaction:
  • Pulse.Gameplay.Event.Interact.Started
  • Pulse.Gameplay.Event.Interact.Ended
• Component change:
  • Pulse.Gameplay.Event.Interact.Component.Changed
• Trigger tags:
  • Pulse.Gameplay.Event.Interact.Started.Trigger
  • Pulse.Gameplay.Event.Interact.Ended.Trigger

When bSendGameplayEventOnInteractionEvent is enabled, ability emits gameplay events for focus/selection/interaction transitions.

Replicated interaction variant

UPulseRepInteractAbility extends UPulseInteractAbility and enables ReplicationPolicy = ReplicateYes.

Key points:

1. Replication eligibility checks actor/component replication status.
2. Replication intent is delegated to ShouldReplicateInteraction(...) on the interactable object.
3. Start/end interaction has server RPC paths (ServerStartInteraction, ServerEndInteraction).

UI integration via MVVM

UMVVMPulseInteract (ModelViewViewModel) mirrors interaction state for UI:

• InteractAbility
• SelectedInteractable
• bIsInteracting
• FocusedInteractables (optional list mode)

It subscribes to native ability events:

• OnInteractableFocusedNative
• OnInteractableLostNative
• OnInteractableSelectedNative
• OnInteractionStartedNative
• OnInteractionEndedNative
• OnInteractableComponentChangedNative

This gives a clean binding surface for interaction prompts and status widgets without polling.