Architecture

Modules

Module	Type	Loading phase	Content
NsInteraction	Runtime	Default	The interface, the option types, the interaction component, the view sensor, and the interactable actor

The .uplugin file lists no plugin dependencies.

Folders

• Source/NsInteraction/Public – NsInteraction.h, NsInteractionTypes.h, NsInteractable.h, NsInteractableActor.h, NsInteractionComponent.h, NsInteractionViewSensor.h.
• Source/NsInteraction/Private – the .cpp file of each header.

Main Classes

Type	Responsibility
INsInteractable	The interface of a usable actor. GetInteractionOption, ExecuteInteraction, OnInteractorEnter, OnInteractorExit. All are BlueprintNativeEvent. The defaults return false or do nothing.
ANsInteractableActor	An actor that implements INsInteractable with one Option from the Details panel. Fires ReceiveInteract (“On Interact”) and OnInteracted.
UNsInteractionComponent	Holds the targets, picks the best option, runs the press and the hold, and sends server requests.
UNsInteractionViewSensor	Traces along a view source, runs the aim assist, and gives one target to the interaction component.
FNsInteractionTarget	An Actor and an optional Part (UPrimitiveComponent). GetLocation() returns the bounds origin of the part, or the actor location.
FNsInteractionOption	The target, ActionId, TapActionId, Title, Prompt, bEnabled, Input, HoldSeconds, Authority, PromptLocation, and Priority. ShowsSame compares the fields that the prompt shows.
ENsInteractionInput	Press, Hold.
ENsInteractionAuthority	Local, Server.
FNsInteractionModule	The module class. It has no startup code.

Data Flow

Targets and options:

1. A sensor calls SetTargets, AddTarget, or RemoveTarget. AddTarget and RemoveTarget build a new list and call SetTargets.
2. SetTargets drops invalid targets, the owner, and repeats. It calls OnInteractorExit on each actor that lost its last target, and OnInteractorEnter on each new actor. Then it calls UpdateTickState and Refresh.
3. Refresh skips targets out of reach (MaxDistanceCm). It calls QueryOption for each other target, scores each option with ScoreOption, and keeps the best. A tie keeps the first target.
4. QueryOption sets OutOption.Target, calls GetInteractionOption, and restores the actor. It keeps the part of the target when the interactable names no part. It sets PromptLocation to the target location when it is zero.
5. When ShowsSame reports a change, Refresh cancels a hold on another target and fires OnOptionChanged.

Input:

1. BeginInteract calls Refresh. A Press option runs at once. A Hold option stores HoldOption and the world time, and turns on the tick.
2. The tick runs the hold action when GetHoldProgress() reaches 1.
3. EndInteract before that cancels the hold and runs TapActionId, when it is set.
4. RunAction does nothing for a disabled option. For a Server option on a machine without authority, it fires OnServerRequest, then calls ServerRequestAction when bSendServerRequests is true. Else it calls ExecuteInteraction.
5. ServerRequestAction (Server, Reliable) calls ExecuteOnServer. ExecuteOnServer checks the reach, builds the option again with QueryOption, and checks bEnabled and that the action is ActionId or TapActionId. Then it calls ExecuteInteraction.

View sensor, each tick where IsControlledHere() is true (a pawn that this machine controls, or an owner that is not a pawn):

1. RefreshFocus traces from ViewSource along its forward vector, TraceDistanceCm long, on TraceChannel. It ignores the owner.
2. The hit part takes the focus when QueryOption gives an option for it.
3. Else, when AssistAngleDeg is above 0, FindAssistTargets runs a sphere overlap of radius TraceDistanceCm. It keeps blocking parts of actors that implement INsInteractable.
4. MeasureViewAngle finds the point of the local bounds box nearest to the view line with a ternary search of 24 steps. A sight trace drops the part when another actor is more than 10 cm in front of the point.
5. The parts sort by angle. The part of the last focus gets AssistStickDeg off its angle. The first part with an option takes the focus.
6. The sensor calls SetTargets with the focus, or ClearTargets.

IsPartInView uses the same trace and the same angle rule, with AssistAngleDeg + AssistStickDeg + ExtraAngleDeg as the limit. It is for a server check of a client request.

Lifetime

• UNsInteractionComponent can tick, but starts with the tick off. UpdateTickState turns it on during a hold, or while RefreshInterval is above 0 and targets exist.
• UNsInteractionComponent::EndPlay clears the targets, so each actor gets OnInteractorExit.
• UNsInteractionViewSensor ticks every frame. BeginPlay finds the first UNsInteractionComponent and the first UCameraComponent on the owner, when none is set.
• ANsInteractableActor makes a USceneComponent named Root and does not tick. Its constructor sets Option.ActionId to Use, Option.Prompt to “Use”, and Option.Authority to Server.

Extension Points

• INsInteractable – Implement it on any actor in C++ or Blueprint:
  • bool GetInteractionOption(AActor* Interactor, UPrimitiveComponent* Part, FNsInteractionOption& OutOption)
  • bool ExecuteInteraction(AActor* Interactor, const FNsInteractionOption& Option)
  • void OnInteractorEnter(AActor* Interactor) and void OnInteractorExit(AActor* Interactor)
• ANsInteractableActor – Blueprintable. Override GetInteractionOption for options that change with game state. Implement ReceiveInteract(AActor* Interactor, FName ActionId) (BlueprintImplementableEvent, “On Interact”). Bind OnInteracted (FNsInteractedDelegate: AActor* Interactor, FName ActionId).
• UNsInteractionComponent::ScoreOption(const FNsInteractionOption& Candidate) const – BlueprintNativeEvent. The default returns Priority * 100000 - Distance.
• OnOptionChanged (bool bHasOption, const FNsInteractionOption& Option) and OnServerRequest (const FNsInteractionOption& Option) – BlueprintAssignable.
• static bool UNsInteractionComponent::QueryOption(AActor* Interactor, const FNsInteractionTarget& Target, FNsInteractionOption& OutOption) – For game checks and custom sensors.
• A custom sensor is any code that calls SetTargets.

Dependencies

Dependency	Kind	Why
Core, CoreUObject, Engine	Public module	Actors, components, collision queries, the camera component, and RPCs

The .uplugin file lists no plugins.

Performance

• Refresh calls GetInteractionOption one time for each target in reach.
• The view sensor ticks every frame on the controlling machine. It runs one line trace and one GetInteractionOption for the hit.
• With the aim assist on and no exact option, it adds one sphere overlap, then one sight trace and 48 box distance checks for each interactable part near the view. It calls GetInteractionOption for each part in the cone until one answers.
• The view sensor calls SetTargets each frame, which calls Refresh. A frame with a focus calls GetInteractionOption one more time.
• OnOptionChanged fires only when the shown prompt changes.

Networking

• UNsInteractionComponent calls SetIsReplicatedByDefault(true). It has no replicated properties. It has one RPC: ServerRequestAction(AActor* Actor, UPrimitiveComponent* Part, FName ActionId), Server, Reliable.
• The RPC needs an owning connection. The owner of the component must belong to the player controller of the client.
• ExecuteOnServer checks the reach, the option, bEnabled, and the action name. It does not check the aim. Call IsPartInView in your own RPC for an aim check. ExtraAngleDeg gives room for the lag of the replicated view.
• ANsInteractableActor sets bReplicates to true. Its Option does not replicate.
• The view sensor runs only on the machine that controls the pawn.

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