Optimization Tips


Performance Optimization

Pool Objects For Instantiation

PUN has a built-in option to instantiate objects from a pool, rather than from a loaded resource (which is kept in-memory to speed up things). Read Using the PrefabPool in the Instantiation doc page.

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Cache RPC Targets

In some cases, you might use a lot of RPCs in your game. Any Component on the target GameObject may implement RPCs, so PUN will use reflection to find the fitting methods. Of course, this is expensive and even wasteful, if the components don't change.

By default, PUN caches a MethodInfo list per Type of script. It does not cache which MonoBehaviours are on the GameObject as potential target.

You can set PhotonNetwork.UseRpcMonoBehaviourCache = true, to cache the MonoBehaviours per PhotonView for RPCs. This speeds up finding the components to call. Should the scripts on a GameObject change, call photonView.RefreshRpcMonoBehaviourCache() to update as needed.

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Send Right Away

RPCs and events raised are not sent at the moment when you call photonView.RPC or PhotonNetwork.RaiseEvent. Instead, they are queued until a periodic routine is called by the PhotonHandler (frequency is set using PhotonNetwork.SendRate). This aggregates messages into fewer packages to avoid traffic overhead but introduces some variable lag. To avoid this lag and you want to send the RPC or event right away call PhotonNetwork.SendAllOutgoingCommands() in the next line.

This makes sense when your game relies on the timing of those messages, examples:

  • timed competitive trivia or quiz games, the quicker the better
  • the opponent is waiting for your turn

However, there are other uses cases for this, like sending a message:

  • before disconnecting
  • before leaving the room
  • before quitting the app (inside OnApplicationQuit)
  • before the app is moved to the background or loses focus (inside OnApplicationPause or inside OnApplicationFocus)

For these cases, you should know that:

  • OnApplicationQuit will not be called on all platforms, on Android for example, this will not be called when the application is terminated by the system. You could use OnApplicationPause instead.
  • Average package loss is typically 1.2%. Even if sent reliable there is no guarantee that what you sent will arrive to destination since the client will be unresponsive or disconnected or no longer joined to the room in case a retry attempt is needed.
  • A message sent in these cases should be relatively small to fit into one package as the client may not have enough time to send multiple fragments.

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Network Traffic Optimization

Compact Serialization

You can optimize traffic quite a bit by having a closer look at what you are sending and how. This can be done later in the development, without a lot of extra hassle. As usual with optimization, start with the most frequently sent messages first.

Often, values and objects are sent with more values than needed to share the state. If your character can't scale, don't sync scale! If your character is never leaning to a side, rotation could be a single float. Actually, a byte may be enough for the rotation without much precision loss. This is fine for non-physical objects.

In general, have a look at what you do in OnPhotonSerializeView and RPCs. You can send a variable amount of values per OnPhotonSerializeView. Sending compact byte arrays is often leaner than registering and sending a lot of Custom Types.

There are some tools that may make your life easier without much hassle. Have a look at the Network Transform Sync package, which provides advanced Transform synchronization with optimized traffic. The Transform Crusher - Free is an option if you just streamline what you send.

Another library that can help with serialization is NetStack. It comes with various other useful features, too.

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Network Culling And Interest Groups

Another technique to save quite some bandwidth is "Network Culling". The team of M2H described their approach here. See Interest Groups

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