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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 (Transition, 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 GPU work each update.

Lifecycle & Materials

  • void RestartFogSystem(): Clears memory/registries, detaches delegates, and rebuilds all 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 path bins revealers into tiles and draws a smooth circle per source. Optional blur + memory/composition run afterward.

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++)
  • What it does: Samples the composed fog at N world positions and returns per-position fog values (0..1) via non-blocking GPU readback.

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 - BlockerRadius (Circle) - bAllFogInstances - 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: - Spawns visual variants (Fogged Mesh slices, Post Process, Volumetric Box, Light Function). - Adopts components/lights from itself and other actors. - Can push area updates into the subsystem. - Adds/removes profiles at runtime.

Properties (high level) - TArray<UFOWProfile*> Profiles – added/removed on BeginPlay/changes. - TArray<FFogVariant> Variants – each targets a Fog Instance, can union/overwrite area, build visuals.

API (high level) - void RebuildFogVisuals() - Adoption: - Components: AdoptComponent(UActorComponent*), UnadoptComponent(UActorComponent*), ClearAdoptedComponents() - Lights: AdoptLight(ULightComponent*), UnadoptLight(ULightComponent*), ClearAdoptedLights()

Variant types (examples) - Fogged Meshes: vertical slice stacks per mesh/instance; binds fog MID. - Post Process: PP blendable with weight/priority/unbounded. - Volumetric Box: proxy mesh + material; configurable half extents. - Light Function: applies fog light-function material to adopted lights.

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
}

Troubleshooting & Tips

  • Nothing shows up? Ensure at least one Fog Instance is enabled and your materials/post process bind the shared MID.
  • Stealth not reacting? Check ActorVisibilityThreshold vs ExploredValue, and the stealth update rate.
  • Expensive frames? Lower LOD, reduce Blur, increase UpdateRate, or disable occlusion if not needed.
  • Multiple instances: Keep them minimal; each has its own full pipeline and render target.