Lessons Learned from Building a Very Large Open World Game in UE5 | Unreal Fest Chicago 2026

This recording of a session presented by Unknown Worlds at Unreal Fest Chicago 2026 covers some of the many lessons learned during the development of ‘Subnautica 2’: a large, open world, multiplayer game in UE5.

Offering insights from the experience of making a multiplayer game with over 100,000 actors and a map many miles by many miles, the team makes a quick stop at each issue, explaining the problem they faced, the solutions they tried—and often, the solution they didn’t try but should have.

The talk covers the performance of a large world—especially in multiplayer—including both at runtime and in editor, using all the latest UE5 tools and techniques such as World Partition, One File Per Actor, Level Instances, Foliage, PCG, and Nanite.

There is also a discussion on how to know when you should roll your own tools and when you should use the inbuilt tools in Unreal Engine, with examples of situations where the team got it right and some situations where they got it wrong.

Most importantly, the session covers the things Unknown Worlds would do differently if they were to make the game again now, so you can bring their learning into your projects. The session has a heavy focus on tools, worldbuilding, and tools for world building, but should be useful for all teams working at scale in Unreal Engine.

Find out more about using Unreal Engine to develop games here: unrealengine.com/uses/games

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