Interest Management

Overview

Interest Management is a set of data culling features, which restrict data replication of specific Network Objects from the Cloud to specific Player Clients. This culling is useful for reduction of network traffic.

Object Interest

Object Interest is a per Network Object setting that indicates how Player interest in that Object should be determined. Players without interest in this Network Object will not receive any updates (Networked Properties as well as RPCs) for this Object from the Server peer.

There are three NetworkObject.ObjectInterest options:

• Area Of Interest: Players with an AOI region which overlaps this Network Object's position in 2d/3d space will be interested in this object.
• Global: All Players receive updates for this Network Object.
• Explicit: Only Players explicitly flagged using SetPlayerAlwaysInterested() will be interested in this Network Object.

IInterestEnter / IInterestExit Callbacks

InterestEnter(PlayerRef player) and InterestExit(PlayerRef player) are called on registered components of a Network Object that implement the IInterestEnter and IInterestExit interfaces, whenever the Local Player gains or loses interest in that Object. Interest can be gained/lost by an Object entering/exiting one of a Player's Area Of Interest regions, or by the Server explicitly setting SetPlayerAlwaysInterested().

These callbacks are also triggered on the Server when in a Server/Client Mode (Dedicated Server/Host). This can be useful for selectively disabling aspects of a Network Object on the Server if it currently out of interest for all player (For example, an NPC may want to disable animations when no Player is interested).

This callback only triggers on clients for interest changes related to the Local Player. Non-Host Players are NOT aware of other Players interest in Objects.

IInterestEnter and IInterestExit implementations in a NetworkBehaviour will automatically be found by the Network Object, however any non NetworkBehaviour derived components with these interfaces need to be manually registered with the NetworkRunner.

IMPORTANT: IInterestEnter will NOT be called when the Object is Spawned on clients, as Player interest is implied by Spawned() happening. You may want to call your InterestEnter() specific handling in Spawned().

IMPORTANT: IInterestExit will NOT be called when the Object is Despawned on clients. You may want to call your InterestEnter() specific handling in Despawned().

Area Of Interest

When this Object Interest mode is selected on a NetworkObject, will use each Client Player’s defined Area Of Interest (AOI) regions to determine if the Network Object is of interest to that player. Player AOI regions are specified by calling the Runner.AddPlayerAreaOfInterest() method.

IMPORTANT: The Replication Features field in the Network Project Config (NPC) must be set to Scheduling and Interest Management for Area Of Interest handling to be enabled.

Clients may have multiple regions defined (for example if the player is operating a remote camera), except when using shared mode. If a Network Object is inside one or more of a Player’s AOI regions, that Player will be interested and will receive server updates for that NetworkObject from the server.

IMPORTANT: In shared mode, adding a new Area of Interest for a player with AddPlayerAreaOfInterest() will delete the previously active one. Shared mode supports only a single Area of Interest per player.

NetworkTransform Requirement

These Fusion's components derive from NetworkTRSP and are AOI compatible:
The Area Of Interest system uses the position value of the NetworkTransform class to determine an Object's position. For any Network Object to participate in the AOI handling, it must have a NetworkTransform component on the same GameObject as the NetworkObject component.

More info on NetworkTransform here.

AddPlayerAreaOfInterest Usage

C#

public class SetAreaOfInterest : NetworkBehaviour
{
  public float Extents = 32f;

  public override void FixedUpdateNetwork()
  {
    if (Runner.IsServer)
    {
      var controller = Object.InputAuthority;
      // Set the controlling players area of interest region around this object
      if (!controller.IsNone)
      {
        Runner.AddPlayerAreaOfInterest(controller, transform.position, Extents);
      }
    }
  }
}

NOTE: Object.SetPlayerAlwaysInterested() can be used in addition to AOI to force player interest in objects, even if they are outside of their AOI range.

Global

This NetworkObject is always of interest to all pPayers. This effectively disables Object culling for this Network Object, and all Players will receive Server updates for this NetworkObject.

Explicit

This Network Object is not of interest to any Player, UNLESS Player interest is specifically added with Runner.SetPlayerAlwaysInterested(). Only Players with explicit interest will receive Server updates for this Network Object.

C#

public class MakeAlwaysInterested : NetworkBehaviour, IPlayerJoined
{
  void IPlayerJoined.PlayerJoined(PlayerRef player)
  {
    if (Runner.IsServer)
    {
      Object.SetPlayerAlwaysInterested(player, true);
      // or
      // Runner.SetPlayerAlwaysInterested(player, Object, true);
    }
  }
}

RPCs and Object Interest

Object Interest will also affect delivery of any non-static RPCs, as these are bound to an instance of a NetworkObject. The RpcInvokeInfo return value may be used on the server to detect and handle failures to send due to a Player not having interest in the NetworkObject instance the RPC is associated with.

C#

[Rpc]
public RpcInvokeInfo RpcFoo()
{
  return default;
}

public override void FixedUpdateNetwork()
{
  if (Object.HasStateAuthority)
  {
    var info = RpcFoo();
    int culledCount = info.SendResult.CulledReceivers.Length;
    if (culledCount > 0)
    {
      //Handling for a target peer being culled from send
      Debug.LogWarning($"{culledCount} receivers culled, possibly due to no Object Interest.");
    }
  }
}