What is the purpose to set culldistance zero in ReplicationGraph?

Development Programming & Scripting Multiplayer & Networking
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1

In Some ReplicationGraphNodes, there is code to set net culldistance zero. and in some condition restore the cull distance back.

For Example:

void UReplicationGraphNode_ConnectionDormancyNode::ConditionalGatherDormantActorsForConnection(FActorRepListRefView& ConnectionList, const FConnectionGatherActorListParameters& Params, FActorRepListRefView* RemovedList)
{
	FPerConnectionActorInfoMap& ConnectionActorInfoMap = Params.ConnectionManager.ActorInfoMap;
	FGlobalActorReplicationInfoMap* GlobalActorReplicationInfoMap = GraphGlobals->GlobalActorReplicationInfoMap;

	// We can trickle if the TrickelStartCounter is 0. (Just trying to give it a few frames to settle)
	bool bShouldTrickle = TrickleStartCounter == 0;

	for (int32 idx = ConnectionList.Num()-1; idx >= 0; --idx)
	{
		FActorRepListType Actor = ConnectionList[idx];
		FConnectionReplicationActorInfo& ConnectionActorInfo = ConnectionActorInfoMap.FindOrAdd(Actor);
		if (ConnectionActorInfo.bDormantOnConnection)
		{
			// If we trickled this actor, restore CullDistance to the default
			if (ConnectionActorInfo.GetCullDistanceSquared() <= 0.f)
			{
				FGlobalActorReplicationInfo& GlobalInfo = GlobalActorReplicationInfoMap->Get(Actor);
				ConnectionActorInfo.SetCullDistanceSquared(GlobalInfo.Settings.GetCullDistanceSquared());
			}

			// He can be removed
			ConnectionList.RemoveAtSwap(idx);
			if (RemovedList)
			{
				RemovedList->PrepareForWrite();
				RemovedList->Add(Actor);
			}

			UE_CLOG(CVar_RepGraph_LogNetDormancyDetails > 0, LogReplicationGraph, Display, TEXT("GRAPH_DORMANCY: Actor %s is Dormant on %s. Removing from list. (%d elements left)"), *Actor->GetPathName(), *GetName(), ConnectionList.Num());
			bShouldTrickle = false; // Dont trickle this frame because we are still encountering dormant actors
		}
		else if (CVar_RepGraph_TrickleDistCullOnDormancyNodes > 0 && bShouldTrickle)
		{
			ConnectionActorInfo.SetCullDistanceSquared(0.f);
			bShouldTrickle = false; // trickle one actor per frame
		}
	}

what is the purpose to do this ?

3

It actually means an infinite number of NetCullDistance. In other words, it can be done without using NetCullDistance. An actor with NetCullDistance set to 0 can be seen as an object with AlwaysRelevant or OnlyRelevantToOwner enabled.

The BasicReplicationGraph.cpp should have something to do with it.