Resolved [Netcode] Creating a new default world

Hello,
I have a menu, from where I can go into a multiplayer game and back.
I'm using Unity Netcode with a custom ClientServerBootstrap, the same shown in the documentation to prevent the auto-startup of client & server worlds. The problem with this, the default world is lacking of some important systems to render some entities in the menu (or a singleplayer section).


So my idea was, adding a new world (MenuWorld) for the menu, so it should look like this:



But the problem I face now is that I don't know how to populate my MenuWorld like a "normal" DefaultWorld (without NetCode) with all the basic systems to render entities etc., without breaking the already existing DefaultWorld. If I try to do the following, the existing DefaultWorld will have no systems anymore, but they are needed to initialize client/server worlds:

Code (CSharp):

1. public class ExampleBootstrap : ClientServerBootstrap
2. {
3.     public override bool Initialize(string defaultWorldName) {
4.         var systems = DefaultWorldInitialization.GetAllSystems(WorldSystemFilterFlags.Default);
5.         GenerateSystemLists(systems);
6.  
7.         var world = new World(defaultWorldName);
8.         World.DefaultGameObjectInjectionWorld = world;
9.  
10.         DefaultWorldInitialization.AddSystemsToRootLevelSystemGroups(world, ExplicitDefaultWorldSystems);
11.         ScriptBehaviourUpdateOrder.UpdatePlayerLoop(world);
12.  
13.         CreateMenuWorld();
14.  
15.         return true;
16.     }
17.  
18.     public void CreateMenuWorld {
19.         World menuWorld = new World("MenuWorld");
20.         DefaultWorldInitialization.AddSystemsToRootLevelSystemGroups(
21.             menuWorld,
22.             DefaultWorldInitialization.GetAllSystems(WorldSystemFilterFlags.Default)
23.         );
24.         ScriptBehaviourUpdateOrder.UpdatePlayerLoop(menuWorld);
25.     }
26. }

I could not find any official documentation regarding this issue. But I was reading this from 5argon which was at least extremely helpful for understanding the basic ideas of worlds.

Another thing I don't get is, what happens if I have 2 worlds with each of them having a RenderSystem? Afaik we can have multiple worlds running at the same time, like client-& server world. Which entities from which world would I see? Both weirdly mixed in one screen?

 

The mistake I made was calling ScriptBehaviourUpdateOrder.UpdatePlayerLoop() twice (one time for each world).
Instead we have to reuse the playerLoop like this:

Code (CSharp):

1. var playerLoop = PlayerLoop.GetDefaultPlayerLoop();
2. ScriptBehaviourUpdateOrder.AddWorldToPlayerLoop(world, ref playerLoop);
3. ScriptBehaviourUpdateOrder.AddWorldToPlayerLoop(menuWorld, ref playerLoop);
4. PlayerLoop.SetPlayerLoop(playerLoop);
5.  

Another mistake was the menuWorld. It seems that we cannot have another non-client/server world in addition to defaultWorld. Because otherwise MultiplayerPlayModeControllerSystem::OnUpdate():229 will break (calling on null)

Code (CSharp):

1. if (simulationGroup != null && simulationGroup == PresentedClient)
2.                 world.GetExistingSystem<ClientPresentationSystemGroup>().Enabled = true;
3.  

Its kind of solvable with adding a ClientPresentationSystemGroup to our 2nd default world (menuWorld), since the menu should only be on "client", but it actual means much more, it would become literally a new client, which gets ghosts loaded etc. So nothing I want to achieve actual.

In the end, I just stick now to my 3 worlds: Default, Client & Server and use the DefaultWorld for all the other stuff, like menu etc.
To get something rendered in the menu, there is a way to load another system-list to the world via

DefaultWorldInitialization.AddSystemsToRootLevelSystemGroups(world, DefaultWorldSystems);

instead of "ExplicitDefaultWorldSystems".
Now entities are getting rendered in the menu too. Problem only is, that the menu entities from the menu scene, are also getting rendered in the client world. And since I cannot just shutdown & recreate the default world when I need to (or can I?), I need to find a better way for handling this issue.

 

@Samsle wondering what you eventually did here?

I'm thinking I'll just run menu stuff from the client world.. would that not work?

 

Hey @krooq,
I can't remember exactly the reasons for having my mainmenu outside of the client world. I guess some netcode systems of client world were interfering with entities of my menu. Also I do not have to clean up my gameplay stuff after going back to menu -just throwing the client world away and recreate a new one later on.

But I think it's up to you, if it works for you within the client world, then just go for it

 

Hello,

@Samsle i am facing kind of the same issue.

The difference is my menu scene does not use any systems, it is fully in Monobehaviour.
But the issue i am facing, it is when i launch the Netcode scene the first time, it works perfectly and when i come back the second time, it does not work..

So i guess i am not disposing the client world properly or i am not loading the Client World correctly..
Can you please share me you code on that ? (if you explain it, it will be awesome.)

I have this assumption : when you load a scene, it starts and loads automatically with a fresh reset.
But i guess that when we open Netcode in a scene some systems/world keeps following us to other scenes.
There is anything to destroy everything when you leave a scene with Netcode/ECS inside? @CMarastoni

 

@CMarastoni Your advice sounds really good, it makes it easier to write "client" systems. For my case e.g., since I wrote my menu system for the default world -which is also running on server side, I had to make a lot of usage of

#if !UNITY_SERVER

to exclude it from running on the server.
But one special advantage of the default world was, that I could render my ghosts in the menu (e.g. for letting the player choose a certain Ghost, without creating a new prefab for that unit), which wasn't possible back then with the client world. But if I think about it now.. maybe it would be possible with just removing some ghost components

@Ali_Bakkal I can't exactly understand your scene flow. In my case I have just one Unity scene for everything and different subscenes for different levels and even my menu, since they are loading way faster then the usual Unity scenes.
But to add some amateur knowledge (maybe wrong), your ECS worlds & systems should be consistent over all Unity scenes afaik, since ECS is independent from the old Unity workflow.


For deleting my client world I do

Code (CSharp):

1. clientWorld.Dispose();

And for creating a new one

Code (CSharp):

1. World clientWorld = ClientServerBootstrap.CreateClientWorld(
2.      World.DefaultGameObjectInjectionWorld,
3.      "ClientWorld"
4. )

And for finding the right world you can use something like this

Code (CSharp):

1. foreach (World world in World.All) {
2.             if (world.GetExistingSystem<ClientSimulationSystemGroup>() != null) {
3.                 clientWorld = world;
4.             } else if (world.GetExistingSystem<ServerSimulationSystemGroup>() != null) {
5.                 serverWorld = world;
6.             }
7.         }

 

Thank you @Samsle

Your code helped me to fix my issue

My mistake was that I did not use the correct code for creating new client world.

 

@Samsle I'm wondering how you handle global manager type data in this setup with multiple worlds?
For example, I need to decide when to show/hide the cursor.
In the main menu world it should always be shown but in the client/gameplay world it should be hidden conditionally.
Where would one store this data and the logic to update it?

As much as I'd prefer a homogeneous programming style, I get the feeling that some of these more "application" level tasks should live in a non DOTS context, i.e. standard mono singleton type manager classes that live outside of any world.

The other alternative I see is to simply stick with the main worlds, default, client and server.

Code (CSharp):

1.  
2. #if !UNITY_SERVER
3. // create client world at startup (from bootstrap perhaps) and use it for menu-y & application level things.
4. #endif
5.  

If the application decides to host a game at runtime it can simply create the server world and start doing that job too.
@CMarastoni would love to get your input how how these worlds are intended to be used in NetCode? Especially the default world.

 

It would be really neat if you could create "SubWorlds" in DOTS. That would solve this issue really neatly.
Essentially Netcode could run in it's own SubWorld which could be disposed when connecting/disconnecting.

 

Yeah this is possible.
The challenge is that the Client world needs information from the Default world, for example, when a level is loaded or a menu is closed. Manually moving that data between worlds is not trivial to manage.
If we could have "SubWorlds" then shared data is easy since everything technically lives in one outer world and the subworld just contains a grouping of systems and data that can easily be managed collectively i.e. disposed. Perhaps subworld is the wrong terminology, what I'm talking about is really just a grouping of systems and data from a world that can easily be disposed.
I feel like DOTS is really missing this concept of modularity that the CustomBootstrap somewhat tries to solve with its system lists.

I'm basically trying to avoid this mess
https://github.com/Unity-Technologi...b6/Assets/Scripts/Game/Main/ClientGameLoop.cs
Shouldn't need a custom loop composed of many loops to integrate with vanilla C# with DOTS.