Unreal Engine Mouse Position in Screen Space to World Location then Sweep / LineCast / RayCast

MousePosRaycast.cpp

void USelectionController::TryGetUnitAtMousePos()
{
	// This is the variable that will be populated by whatever we hit with our sweep
	FHitResult HitResult;
	
	if(SweepToMousePos(HitResult))
	{
		HitResult.GetActor()->Tags.Add("Selected");
		//Draw a sphere where we hit
		DrawDebugSphere(GetWorld(), HitResult.ImpactPoint, 100, 10,FColor::Green, false, 5);

		//If our hit result = the type of actor we want to hit
		if(Cast<ABaseUnit>(HitResult.GetActor()))
		{
			// Do something with it
			UnitSelectionManager->SelectSingleUnit(Cast<ABaseUnit>(HitResult.GetActor()));
		}
	}
}

bool USelectionController::SweepToMousePos(FHitResult& HitResult) const
{
	APlayerController* PlayerController = GetWorld()->GetFirstPlayerController();
	FVector WorldLocation;
	FVector WorldDirection;

	//This is where the mouse screen pos gets converted to world pos
	if(PlayerController->DeprojectMousePositionToWorld(WorldLocation, WorldDirection))
	{
		//Start and end points of our sweep/trace
		FVector Start = WorldLocation;
		FVector End =  Start + WorldDirection * 1000000;
	
		DrawDebugLine(GetWorld(),Start, End, FColor::Red);
		DrawDebugSphere(GetWorld(), End, 10, 10,FColor::Blue, false, 5);
		
		//Linecast / Raycast
		return GetWorld()->LineTraceSingleByChannel(HitResult,Start,
			End,ECC_GameTraceChannel1);

		//The shape we will use for our sweep
		FCollisionShape Sphere = FCollisionShape::MakeSphere(10.f);

		//Since we are using a sphere, we are effectively doing a "SausageCast"
		return GetWorld()->SweepSingleByChannel(HitResult,Start,
			End,FQuat::Identity, ECC_GameTraceChannel1, Sphere);
	}