How to create a Large MMO map?

I want to ask How can I make a MMO map? I read some articles about level streaming but this is a multiplayer game so will it work? And if yes, how should I do it?

Level Streaming is the way to go for sure. Look into “World Composition” and at Tiled Terrains, This allows you to split up your world into little chunks so that you don’t need to render it all and you can have high detail like a normal game would with minimal lag. You then load in the new chunks when you enter a zone for example and then unload the ones further away. The way World of Warcraft does this is to have distance fog to hide the zones unloading which is the big grey misty looking wall you see in the distance. The multiplayer bit is the bit you’re going to run into issues because of stuff like creatures and other AI. I would if I were you work out some solution for putting these on the persistent level (Base level).

As for getting the actual MMO running in Unreal is it’s own challenge and it’s a stupidly big task. The stock UE4 server isn’t really cut out for running something as big as an MMO unless you do some sneaky strategies like having clusters and then loading the player into different servers. For this if I were you I would look into Raknet and 3rd party solutions or editing the source code for the default UE4 server.

I did not find any solutions for level streaming in multiplayer… All are just for the single player.

Well you may not actually need to, What I would do is have the terrain and map tiles only load for the client when they walk near them. Then just have all of the NPC’s and all multiplayer elements on the persistent level. This might not be the best way to go but that’s deffo the way I would go about it. The map itself would potentially be completely client side meaning that there’s less resources needed by the MMO server.

As for actually implementing the level streaming itself I would do this using trigger boxes that are the size of zones. Then use these trigger boxes to load/unload the levels you need.