Line trace raycast for interaction system

Pattern: Input trigger → LineTraceSingle(CameraLocation, CameraLocation + ForwardVector * Distance, Visibility, false, MakeArray(Self), None) → Branch(ReturnValue) → True: BreakHitResult → HitActor → CastTo InteractableInterface → call Interact. End pin is world POSITION not direction. Use DrawDebugType ForOneFrame during dev.

Line trace from camera to detect what player is looking at

Pattern: GetPlayerController → GetPlayerViewPoint(outputs Location,Rotation) → GetForwardVector(Rotation) → Multiply_VectorFloat(A=Forward, B=TraceDistance) → Add_VectorVector(A=CameraLocation, B=Offset) → LineTraceByChannel(Start=CameraLocation, End=TraceEnd). GetPlayerViewPoint exec in='execute', exec out='then', outputs: 'Location' (Vector) and 'Rotation' (Rotator).

Niagara particle effect at impact point from line trace

Pattern: LineTraceByChannel → Branch(hit=true) → BreakHitResult → SpawnSystemAtLocation(SystemTemplate=NS_Impact, Location=ImpactPoint, Rotation=MakeRotFromX(ImpactNormal), Scale=(1,1,1), bAutoDestroy=true). Use MakeRotFromX with ImpactNormal to orient effect to surface normal. NS_ prefix is convention for Niagara Systems. SpawnSystemAtLocation is in UNiagaraFunctionLibrary. bAutoDestroy=true means the component cleans itself up after the effect completes.

Interactable interface system with line trace from camera

Pattern: BPI_Interactable interface with Interact(APawn* Caller) and GetInteractText(). Player Tick: GetPlayerCameraManager → GetCameraLocation/Rotation → LineTraceSingle(CamLoc, CamLoc + Forward*InteractDistance) → BreakHitResult → HitActor → DoesImplementInterface(BPI_Interactable) → True: show UI prompt, store as FocusedActor. Interact input → call Interact(Self) on FocusedActor.

Procedural mesh placement on terrain using line trace downward

Pattern for snapping object to ground: GetActorLocation → Add Vector(Z=+1000) → as TraceStart. GetActorLocation → Subtract Vector(Z=1000) → as TraceEnd. LineTraceByChannel(Start=TraceStart, End=TraceEnd, TraceChannel=Visibility) → Branch(ReturnValue=true) → BreakHitResult → SetActorLocation(NewLocation=ImpactPoint) → SetActorRotation(NewRotation=MakeRotFromZ(Normal)) [align to surface normal]. MakeRotFromZ takes a 'Z' input Vector and outputs Rotator aligned to that normal.

LineTraceByChannel — raycast along a line and return first hit

TraceChannel: ETraceTypeQuery::TraceTypeQuery1=Visibility, TraceTypeQuery2=Camera. DrawDebugType: None/ForOneFrame/ForDuration/Persistent.

LineTraceSingle — raycast single hit by channel

UKismetSystemLibrary::LineTraceSingle. WorldContextObject is hidden. End pin is world position, not direction.

DrawDebugLine — draw debug line in world

UKismetSystemLibrary::DrawDebugLine.

LineTraceMulti — raycast returning multiple hits

GetHitResultUnderCursorByChannel — trace under mouse cursor

APlayerController method. Great for click-to-interact games.