Persistent world with UE4 (not an MMO)

[Daniel_K]

@Kaiserludi;633287

Hi Daniel.

Yes, a persistent world is definitely possible with Photon.

However you will also definitely need to dig a bit into C++ and C# coding to achieve what you want (or let Exit Games do all the Photon related coding work for you if you are willing to use our consulting services).

Thanks for elaborate answer, but to be honest, this all sounds much more than just “dig a bit into coding”. At least for someone who doesn’t have any real experience with UE itself. Adding another such complex layer seems kinda over my head currently. I’ve also got the impression that Photon would not really help with actual serialization of the game world and I am also unclear if it would even help with transmitting only small portions of game world to player based on his location. All this is certainly the biggest part of the whole problem which I would need to develop anyway. Am I right?

@jwatte;633289

The reason most MMOs don’t allow the user to affect the world permanantly, is exactly that it’s really hard to provide all those modifications to a player when they log on!

Before Minecraft became a thing I couldn’t agree with you more, but since then it’s becoming more than a standard to have a chance of influencing the world around you in a permanent way. I could come up with handful of games with such ability I know of and I am sure there is much more I do not know. I’ve already said that we don’t want to use “MMO” sticker. I would say it’s more harmful than helpful to have that sticker these days as it got kinda bad reputation from all those static MMOs.

@jwatte;633289

One option would be to use the built-in savegame system. Mark the players themselves (and their inventory) as NOT SAVED, and save all the actors that are permanent in the world.
Now, saving is kind-of expensive and takes a while, so it will stop world processing for a short time when it happens, so you probably only want to do it once in a while (every 15 minutes?)
Once the file is saved, you might want to use some other script/feature to copy a backup of the save file to somewhere else, so you can restore if the server dies.

I do remember such system from development of Ultima Online server when I was young It was saving the world every 10 minutes and everyone had to stop doing stuff I don’t think it’s a good system.

Funny thing is that we actually want player characters to be persisted as a part of the world. Once the player logs off, the character is taken by AI and starts wandering and doing simple tasks to create impression of alive world. AI should even be able to fight with other player and so on

@jwatte;633289

The other option is to go the virtual world approach, and write a separate database record every time the player affects the world. The state of the world is then derived by re-running all of those records forward in time. There is no support built-in to any game engine I know (except the virtual-world engines/systems) for this, because it’s highly context dependent.
You will generally have to apply two kinds of optimizations to make this viable:

• Player will only get world modifications within some area around where they are – say, 500 meters or so? If you support burning down entire forests, and have sight lines from a mountaintop into that forest, your radius needs to be very big, so don’t support that!
• Changes will happen in some order (sequence) and have a sequence number. Players will cache data they received until sequence X, and server will only send changes that happened since sequence X when the player logs on. Server may even “bake” the end result of changes until some point Y, and provide as a patch file, when the user logs on (once a day? once a week?)

In general, though, persistent world changes are REALLY HARD and require heavy duty attention to the interaction between implementation, gameplay/design, networking, and persistence.
If you’ve only developed in JavaScript before, chances are you haven’t really learned all the tricks of low-level optimization that need to be applied to make these things tractable on typical user network/hardware. But it’s super fun to learn this stuff, so I envy your future

Thank you for this, very helpful and it almost does sound like it’s actually kinda easy to do In Javascript we currently do have append-like system for saving game state and it’s doing occasional housekeeping to apply these changes to the original game state thus yielding new updated game state. However it does not scale well because we need to have multiple processes (due to NodeJS being single threaded).

Regarding distance of sending updates it’s actually pretty easy in our case as it will be underground and in most places there will a pitch dark so generally player needs to get only data for a location around him.

Sadly this is all just a theory, I can imagine how I would do it in Javascript, but thinking about UE4 boundaries, it’s almost unthinkable how I would create the world map dynamically client side based on data received from the server.