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Fog of War (UE5) - API Reference

This page documents the public API of the Fog of War plugin as exposed by the Subsystem, Actor Components, and the Manager. It’s written for Blueprint and C++ users.

Concepts & Data Types

  • Fog Instance: A named fog layer (render target + runtime settings). Multiple instances are supported and updated in order.
  • Revealers: Vision sources that write visibility (smooth circles) into the fog.
  • Blockers / Occluders: Circular blockers and/or depth-capture-driven occlusion; optional height-aware checks and distance field.
  • Stealth: Policy that hides, fades, or “freezes as ghost” when an actor is not visible in fog.

Key structs / enums (Blueprint-exposed):

  • FFOW_AreaSettings - Center (FVector), FullExtents (FVector2D), YawDeg (float).
  • FFOW_RuntimeSettings - Toggles (Enabled/Freeze/ShowFog/ShowMemory/FreezeMemory), Visual (ExploredValue, ActorVisibilityThreshold, SmoothFalloff, Blur settings), Blending (Transitiontype, FadeInRate, RelaxRate, ForgetRate), Occlusion (RayMode, DFScale, UseHeightOcclusion, Capture options), Performance (LOD, UpdateRate, TileSize/MaxPerTile, UpdateOnlyOnChanges).
  • FVisionData - WorldPos, RangeWS, EyeHeightOffsetWS.
  • EFOWActivationPolicy, EFOWVisibilityPolicy, EFOWHiddenMode, EFOWOcclRayMode, EFOW_TransitionBehaviour.

Subsystem (UFOWSubsystem)

Access via:

auto* FOW = GetWorld()->GetSubsystem<UFOWSubsystem>();

The subsystem (client-side) owns all Fog Instances and dispatches the GPU work.

Lifecycle & Materials

  • void ResetFogSystem(): Clears memory/registries, detaches delegates, and resets the state.
  • void ClearAllMemory(): Clears “last seen” memory for all instances.
  • bool ClearMemory(FName FogInstance = NAME_None): Per-instance memory clear (NAME_None = primary).
  • UMaterialInstanceDynamic* AcquireSharedMIDForFogInstance(FName FogInstance, UMaterialInterface* Base): Returns a shared, auto-updating MID with fog parameters & RT bound.

Fog Instance Management

  • FName GetPrimaryFogInstanceName() const
  • void GetFogInstancesNames(TArray<FName>& Out)
  • bool AddOrReplaceFogInstance(const FFOW_FogConfig& Config)
  • bool RemoveFogInstanceByName(FName Name)
  • void AddProfile(const UFOWProfile* Profile) / void RemoveProfile(const UFOWProfile* Profile)
  • bool GetFogInstanceRuntime(FName, FFOW_RuntimeSettings& Out) const
  • bool GetFogInstanceArea(FName, FFOW_AreaSettings& Out) const

Runtime Settings

All setters return bool and accept NAME_None to target the Primary instance.

Toggles

  • SetFogInstanceEnabled(FName, bool)
  • SetFogInstanceFreezeState(FName, bool)
  • SetFogInstanceShowFog(FName, bool)
  • SetFogInstanceShowMemory(FName, bool)
  • SetFogInstanceFreezeMemory(FName, bool)

Visuals

  • SetFogInstanceExploredValue(FName, float /*0..1*/)
  • SetFogInstanceActorVisibilityThreshold(FName, float /*0..1*/)
  • SetFogInstanceSmoothFalloff(FName, float /*0..1*/)
  • SetFogInstanceBlurIterations(FName, int32)
  • SetFogInstanceBlurRadius(FName, int32)
  • SetFogInstanceBlurSigma(FName, float)

Blending

  • SetFogInstanceTransitionMode(FName, EFOW_TransitionBehaviour)
  • SetFogInstanceFadeInRate(FName, float)
  • SetFogInstanceRelaxRate(FName, float)
  • SetFogInstanceForgetRate(FName, float)

Occlusion

  • SetFogInstanceOcclusionRayMode(FName, EFOWOcclRayMode)
  • SetFogInstanceDFScale(FName, int32 /*>=1*/)
  • SetFogInstanceUseHeightOcclusion(FName, bool)
  • SetFogInstanceUseDepthCaptureOcclusion(FName, bool)
  • SetFogInstanceCaptureUsesShowOnly(FName, bool)
  • SetFogInstanceUpdateOnlyIfTransformChanged(FName, bool)

Performance

  • SetFogInstanceLOD(FName, int32 /*1..32*/)
  • SetFogInstanceUpdateOnlyAtCrucialChanges(FName, bool)
  • SetFogInstanceTileSize(FName, int32)
  • SetFogInstanceMaxPerTile(FName, int32)
  • SetFogInstanceUpdateRate(FName, float /*seconds, >= 0.01*/)
  • void SetStealthActorUpdateRateSeconds(float Seconds)

Bulk

  • bool SetFogInstanceRuntime(FName, const FFOW_RuntimeSettings&)

Area & Transform

  • bool SetFogInstanceArea(FName, const FVector& Center, const FVector2D& FullExtents, float YawDeg)
  • bool ExpandFogInstanceAreaToInclude(FName, const FVector& OtherCenter, const FVector2D& OtherFullExtents, float OtherYawDeg /*keeps A’s yaw*/ )

Vision Sources (Revealers)

Actor-based

  • void RegisterVisionSource(AActor* Source, float RangeWS, float EyeHeightOffsetWS = 0.f)
  • void UnRegisterVisionSource(AActor* Source)
  • void ClearAllVisionSources()

Static (handles)

  • int32 AddStaticRevealer(FVector WorldPos, float RangeWS)
  • void RemoveStaticRevealer(int32 Handle)
  • bool SetStaticRevealerRange(int32 Handle, float NewRangeWS)
  • void ClearAllStaticRevealers()

The GPU pipeline later bins revealer informration into tiles based on their location and draws a smooth circlearound them.

Blockers / Occlusion

Blockers can be actor-based (follow the actor) or static (fixed world position). Occlusion can come both from either circles around these blockers or from depth captures.

Actor-based

  • void RegisterBlocker(AActor* Actor, float RadiusWS, FVector LocalOffsetWS = FVector::ZeroVector, float HeightWS = 0.f, bool bUseHeightLayer = false)
  • void UnregisterBlocker(AActor* Actor)
  • void ClearAllBlockers()

Static (handles)

  • int32 AddStaticBlocker(const FVector& WorldPos, float RangeWS, float HeightWS = 0.f, bool bUseHeightLayer = false)
  • void RemoveStaticBlocker(int32 Handle)
  • void ClearAllStaticBlockers()
  • bool SetStaticBlockerRange(int32 Handle, float NewRangeWS)
  • bool SetStaticBlockerHeight(int32 Handle, float NewHeightWS)
  • bool SetStaticBlockerUseHeightLayer(int32 Handle, bool bUseHeightLayer)

Depth-capture (for capture-based occlusion)

  • int32 AddCaptureActorToAllFogInstances(AActor* Actor)
  • int32 RemoveCaptureActorFromAllFogInstances(AActor* Actor)
  • bool AddCaptureActorToFogInstance(FName FogInstanceNameOrNone, AActor* Actor)
  • bool RemoveCaptureActorFromFogInstance(FName FogInstanceNameOrNone, AActor* Actor)
  • bool ClearCaptureActorsForFogInstance(FName FogInstanceNameOrNone)

Use circle blockers for cheap, radius-based occlusion (walls, big rocks) and capture actors when you want height-aware, mesh-accurate occlusion.

Stealth Actors

  • void RegisterStealthActor(AActor* Actor, EFOWHiddenMode HideMode, EFOWVisibilityPolicy Policy)
  • void SetStealthVisibilityPolicy(AActor*, EFOWVisibilityPolicy)
  • void SetStealthHiddenMode(AActor*, EFOWHiddenMode)
  • void SetStealthActorHideThresholdOverride(AActor*, float ThresholdOrNegative /*<0 = system default*/ )

Position Queries (GPU)

  • Handle types: FFOWPositionQueryHandleBP (Blueprint) / FFOWPositionQueryHandle (C++ internal)
  • What it does: Samples the composed fog at N world positions and returns per-position fog values (0..1) via non-blocking GPU readback (plus visibility flags via a threshold).

Threshold behaviour

  • Threshold < 0 → use each Fog Instance’s own ActorVisibilityThreshold.
  • Threshold >= 0 → use this override for the whole query (0..1).

Blueprint latent helpers

  • void CheckPointVisibility(UObject* WorldContextObject, FLatentActionInfo LatentInfo, FVector WorldPosition, bool& bIsVisible, float& OutValue, float Threshold = -1.0f)
  • void CheckPointsVisibility(UObject* WorldContextObject, FLatentActionInfo LatentInfo, const TArray<FVector>& WorldPositions, TArray<bool>& OutVisible, TArray<float>& OutValues, float Threshold = -1.0f)

Use these when you just need a one-shot answer in Blueprint (they complete once the GPU readback is ready).

Low-level handle API

  • FFOWPositionQueryHandleBP StartPositionQuery_Auto(const TArray<FVector>& WorldPositions, float ThresholdOverwrite = -1.0f)
  • bool PollPositionQueryResults(FFOWPositionQueryHandleBP Handle, TArray<bool>& OutFlags, TArray<float>& OutValues)
  • FFOWPositionQueryHandleBP StartPositionQueryForActors_Auto(const TArray<AActor*>& Actors, float Threshold = -1.0f)

Typical pattern: start a query (positions or actors), store the handle, then call PollPositionQueryResults in a later frame until it returns true, at which point OutFlags / OutValues are valid.

Actor Components

UFOWVisionComponent

Attach to reveal fog around the actor.

Properties

  • Activation (Manual / AutoOnBeginPlay)
  • VisionRange (cm)
  • EyeHeightOffset (for height-aware occlusion)

Blueprint API

  • ActivateForFOW(), DeactivateForFOW()
  • SetVisionRange(float), GetVisionRange()
  • SetEyeHeightOffset(float)
  • IsRevealing()

On activation it registers with the subsystem; changing range/offset while active re-registers to apply changes.

UFOWBlockerComponent

Attach to provide occlusion either as simple circles or via depth capture writes into one or many fog instances.

Modes

  • Circle (radius)
  • CaptureWriter (SceneCapture-driven occlusion input)

Properties

  • Activation (Manual / AutoOnBeginPlay)
  • BlockerRadius (Circle, cm)
  • bAllFogInstances (CaptureWriter)
  • TargetFogInstances (CaptureWriter)

Blueprint API

  • ActivateForFOW(), DeactivateForFOW()
  • SetMode(EFOWBlockerMode)
  • SetBlockerRadius(float)
  • AddToAllFogInstancesCapture(), RemoveFromAllFogInstancesCapture()
  • AddToFogInstanceCapture(FName), RemoveFromFogInstanceCapture(FName)

UFOWStealthComponent

Attach to actors that should hide/fade/freeze when not visible in fog. Handles material fades and optional ghost sync.

Properties

  • Activation
  • HiddenMode (Hide, FreezeWithGhost)
  • VisibilityPolicy (FogDriven, AlwaysVisible, AlwaysHidden)
  • bUseStealthVisibilityThresholdOverride + StealthVisibilityThresholdOverride (0..1)
  • FadeSeconds, FadeParamName, bHideActorAfterFadeOut

Blueprint API

  • ActivateForFOW(), DeactivateForFOW()
  • SetHiddenMode(EFOWHiddenMode)
  • SetVisibilityPolicy(EFOWVisibilityPolicy)
  • SetStealthVisibilityThresholdOverride(bool bEnable, float Threshold01)
  • SetFadeSeconds(float)
  • SetFadeParam(FName)
  • Events: OnBecameVisible, OnBecameHidden

Manager (AFOWManager)

A convenience actor that wires profiles, premade *visual fog variants into the Fog of War subsystem.
It just helps to build and maintais the visuals + Fog Instance areas and can also be referenced as an example on how to setup custom visuals.

Responsibilities

  • Registers / unregisters UFOWProfile assets with UFOWSubsystem.
  • Spawns visual variants (Layered Meshes, Post Process, Volumetric Box, Light Function) for chosen Fog Instances.
  • Optionally updates Fog Instance areas from its own bounds / adopted geometry.
  • Temporarily overrides light functions and restores them on cleanup.

Key properties

  • TArray<UFOWProfile*> Profiles
    Profiles to add/remove on BeginPlay/EndPlay (external Fog Instances).
  • TArray<FFogVariant> Variants
    Per-Fog-Instance visual setup (type, materials, box size, area sync, adopted actors).

Core API

  • Profiles / variants:
    • void ReapplyProfiles() - re-registers Profiles with the subsystem.
    • void RebuildFogVisuals() - clears and rebuilds all visuals from Variants.
  • Component adoption:
    • bool AdoptComponent(UActorComponent*)
    • bool UnadoptComponent(UActorComponent*)
    • void ClearAdoptedComponents()
  • Light adoption:
    • bool AdoptLight(ULightComponent*)
    • bool UnadoptLight(ULightComponent*)
    • void ClearAdoptedLights()

Variant types (summary)

  • Fog Layered Meshes - vertical slice stacks; bind a shared fog MID; can use the primitives of adopted components for the slices.
  • Post Process - local or global PP blendable that samples the fog texture; optional area update from a box.
  • Volumetric Box - proxy mesh volume with fog material; box size can come from BoxHalfExtent or adopted components.
  • Light Function - applies a fog-aware light function MID to adopted lights and/or lights listed in the variant.

Project Settings & Profiles

Project Settings → Plugins → Fog Of War (UFOWSettings)

  • DefaultFogInstances - initial fog instances (one internal allowed; others external).
  • GlobalFogDefaultUpdateRate - cadence fallback.
  • GlobalStealthActorUpdateRate - stealth polling rate.
  • Default materials for Manager variants (Fogged Mesh / Volumetric Box / Post Process / Light Function).

Profiles (UFOWProfile)

  • Data assets with external-only Fog Instances.
  • Add/remove via Subsystem or Manager at runtime.
  • Names are sanitized (unique, non-empty).

Examples

Blueprint quick starts

// Reveal an actor on BeginPlay
Add Component: FOWVisionComponent
  Activation = AutoOnBeginPlay
  VisionRange = 2500

// Hide an enemy when not visible
Add Component: FOWStealthComponent
  HiddenMode = Hide
  VisibilityPolicy = FogDriven
  FadeSeconds = 0.25
  FadeParamName = "FOW_Visibility"

// Use a blocker that writes into depth captures of all instances
Add Component: FOWBlockerComponent
  Mode = CaptureWriter
  bAllFogInstances = true

C++ snippets

// Toggle memory on the primary instance
if (auto* FOW = GetWorld()->GetSubsystem<UFOWSubsystem>())
{
    FOW->SetFogInstanceShowMemory(NAME_None, true);
}

// Bind a MID with fog params and RT to a mesh
if (auto* FOW = GetWorld()->GetSubsystem<UFOWSubsystem>())
{
    UMaterialInstanceDynamic* MID = FOW->AcquireSharedMIDForFogInstance(NAME_None, BaseMat);
    Mesh->SetMaterial(0, MID);
}

// Register a static revealer
if (auto* FOW = GetWorld()->GetSubsystem<UFOWSubsystem>())
{
    int32 Handle = FOW->AddStaticRevealer(GetActorLocation(), 1800.f);
    // Store handle to update or remove later
}