Ue4 struct replication

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Replication Graph

Am I right in assuming that both structs and arrays always get replicated as a whole and not per member-property or element? Many times a struct is the only sensible way to organize your data in. Think of a character stat and skill system for example. It can have dozens of values and "derived" values and would ideally also contain things like health that potentially change very frequently.

Replicating the whole struct every time a single value changes will force me to use bad style and put lots values "loosely" into an object, which makes re-usability impossible. Let's assume I have some kind of "game event" structure that has a date-time member, maybe a text, maybe some coordinates and references, which are needed to make changes in the world by the clients that can't be replicated directly because of non-replicated actors, basicallyonly reconstructed based on the event-info.

If I would send these as a parameter of some server function every time an event occurs, then anyone joining the game afterwards will never receive these events. This leaves me with two options, the way I see it. I can either use a seperate replicatable UObject for each event or have a replicated array of event-structs in the game-state or wherever.

Now, if the number of events will be in the thousands, then the limit of replicatable objects would be reached at some point using UObjects. Besides this kind of object spam just can't be right.

On the other hand, if I use structs inside an array, and new events are added almost every second, then my fear is that the whole array will be sent to clients every time, even though only the last element would have to be sent. So then these thousands of structs inside the array would be broadcast to every client every time a new event gets added and probably kill the network traffic sooner or later. Can anyone confirm this? Or maybe the engine internally knows what array-elements need to be sent after all??

ue4 struct replication

If not, I guess I would have to make it more complicated and "manually" have the number of received events tracked for each client and use a function to send only new structs individually or in small arrays as parameter to individual clients. But I wouldn't bother with that unless I have to. The question isn't so much whether the data-members get replicated or not, but if they get replicated "selectively" only the ones that actually changed or if every struct and array always replicates as a whole, producing lots of redundant network traffic.

That's an interesting idea. I'd rather have all variables replicate though, but not redundantly. Attachments: Up to 5 attachments including images can be used with a maximum of 5. Answers to this question.A quick way to define Portals is to see them as a way to walk from one space to one another. Some very popular games used that concept for visuals and even gameplay mechanics :. Prey, Portal is likely the most well known of the three, however in my case it is Prey which always fascinated me and that I always wanted to copy.

However with the current versions of Unreal Engine I was finally able to manage the right effect :. By this principle we can stick two spaces next to each other even if they are far away.

The window is like a mask that allows us to know where and when to display the other space instead of the original one. Since the original point of view is replicated to the other place it gives the illusion of being continuous.

In the graphic above, the Capture device a SceneCapture in UE4 is located in front of a space that match one visible from the player point of view. Everything visible after the line is replaced by what the capture can see. In case of a portal what we want is a near clipping plane which will mask out objects visible before the portal.

How does that translate into the Unreal Engine then? I build my system around two main classes which are managed by the PlayerController and the Character. Please note that the rest of the tutorial expect you to have a access from the code to a Character and PlayerController class.

The goal of the actor will be to provide information relative to the player to compute different positions and rotations. It will also handle detecting when the player is crossing or not the portal and teleport him. Here is the header :. As you can see, most of the behaviors I described in the first place are present here. The constructor here focus on the setup of root components. The PortalRootComponent here will be the basis of all the Portal related computation later. The function takes advantage of the FPlane struct from UE4 to perform the computation.

This function checks if a point crossed the portal plane. This is were we use the old position in order to know how the point is behaving. This function is generic so that it could work with any Actor, but in my use-case it is only for the player.This is a crash course on getting started, though is not a full tutorial on networking gameplay code.

A class must first be marked to replicate. Without doing this, a blueprint actor spawned on the server will not spawn on clients. This is done in the blueprint defaults, under replication:. The UE4 Editor provides a built in way for testing multiplayer games.

This will launch a separate editor window for each player, and automatically connect them into a multiplayer game. This is the easiest way to test and iterate on multiplayer gameplay. It will be important to only run certain parts of your blueprint logic on the server.

ue4 struct replication

For example, the server should be authoritative over the health value of each actor. Only the server should handle changing health.

ue4 struct replication

Clients should be free to run cosmetic logic, but should not run gameplay critical code on their own. Replicated variables are used to replicate state. Replicated variables are sent from server to client only. That is, the server's value of a replicated property is sent down to all clients. To make a property replicated, simply select the Replicated or RepNotify from the Replication drop down in the variable details panel. This is useful when you need to do additional work based on a replicated variable.

For example, you may replicate Health down as an integer. In Health's RepNotify event you may look at the health value and apply cosmetic damage effects swap mesh, apply damage decals, play sounds, etc. It is more efficient to apply the cosmetic damage in a RepNotify than to replicate each cosmetic effect down individually.

If you select RepNotify, a function will automatically be added to your blueprint. Just implement a body in this function and will be called automatically. Events can also be replicated as RPCs remote procedure call. An event can be called on one machine and replicate to another where it is executed. To use this feature, create a new custom event in your event graph. Click on the custom event and edit the Replication settings in the details view:.

Multicast events are called on the server and are executed on the server and all connected clients. These can be called on any replicating actor.

1.4 - Variable Replication [RepNotify]

Multicast events are best for replicating transient events e. A Server RPC is only executed on the server. When the client reaches the node to call the custom event, he will send a packet to the server telling it to execute the event on the actor.

The client himself will not execute the event locally. Server RPCs can only be called by a client who owns the actor executing the event graph.But when you have to send data, you should try to use some form of compression to reduce the bandwidth.

You can leverage some quantization functionalities exposed by the engine such has Vector quantization [ b ] [ c ] [ d ] [ e ] and Quaternion quantization [ f ] [ g ]. You can do custom compression before the data is sent to the network and decompression after the data is received.

If you define this method, the engine will use it while serializing and deserializing your struct for networking both during properties replication and RPC. With this technique, class code specialization is moved from runtime to compile time. The basic idea is to resolve at compile time what is known at compile time. You can find out more about the use of FArchive in this article by Rama.

In the first 3 lines the current values are quantized from float to byte values. Here is an example:. It contains also commented code examples on how to implement custom struct serialization; I strongly recommend reading it. Basically, if you want to replicate a TArray efficiently, or if you want events to be called on client for adds and removal, just wrap the array into a ustruct and use FTR.

Here is what the code documentation says about FTR:. MarkItemDirty a ; DeltaTest. MarkItemDirty DeltaTest. Home Projects Music Sheets Contact. If false, the property will be considered 'dirty' and will replicate again on the next update.

If an actor's Actorchannel is not fully mapped, properties referencing it must stay dirty. Generally, you will want to return false from your ::NetSerialize. This should be mutually exclusive with WithIdentical. This should be mutually exclusive with WithIdenticalViaEquality.Base struct for wrapping the array used in Fast TArray Replication.

Called after updating all existing elements with new data and after the elements themselves are notified. Helper function for FastArrayDeltaSerialize to consolidate the logic of whether to consider writing an item in a fast TArray during network serialization. We're working on lots of new features including a feedback system so you can tell us how we are doing.

It's not quite ready for use in the wild yet, so head over to the Documentation Feedback forum to tell us about this page or call out any issues you are encountering in the meantime. Inheritance Hierarchy. Select Skin. Welcome to the new Unreal Engine 4 Documentation site! We'll be sure to let you know when the new system is up and running. Post Feedback. List of items that need to be re-serialized when the referenced objects are mapped.

Performs "standard" delta serialization on the items in the FastArraySerializer. Called after adding all new elements and after the elements themselves are notified.

Called before removing elements and after the elements themselves are notified.Networking and Multiplayer. Component Replication. Actor Replication. Networked Play In Editor. In order to view both Server and Client perspectives, on the Play dropdown, set the Number of Clients field to 2.

Oftentimes, it is desired to execute some logic in response to the value of a replicated variable changing. Variables that are marked RepNotifyhave a special function called automatically any time the value is changed, on both Network Authority and Remote Machines. In this example, the Network Authority controls changing a scalar value indicating which color the streetlight should display using a RepNotify variable.

When the value is changed, the auto-generated OnRep function is called, which in this example then updates a material parameter. Setting a variable to RepNotify can be done through the Details panel of the variable under the Replication drop down menu. With this setup, both Client and Server see the same sequence executed for the streetlight when playing in game.

We're working on lots of new features including a feedback system so you can tell us how we are doing. It's not quite ready for use in the wild yet, so head over to the Documentation Feedback forum to tell us about this page or call out any issues you are encountering in the meantime. Unreal Engine 4. See Also. Blueprint Breakdown. Select Skin. Welcome to the new Unreal Engine 4 Documentation site!

We'll be sure to let you know when the new system is up and running. Post Feedback.Changes to the official Unreal Engine Wiki. Posts Latest Activity. Page of Filtered by:. Previous 1 2 3 4 11 17 template Next.

UE4 Tutorial: Multiplayer Replication (Part 1)

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Thanks so much to those that are coordinating the initiative and have reached out! Last edited by Amanda. Schade ;PM. Tags: None. This isn't very helpful, Amanda!