World Partition
Splits an open game world into a grid that streams in and out automatically around the camera, replacing hand-authored level cells.
Epic introduced the system in Unreal Engine 5 (2021) to replace the older World Composition and manual level streaming. The world is stored as one large document but divided internally into cells; the engine loads only the cells within a radius of the player and discards the rest. A Data Layer lets the same ground show different content — day/night, before/after an event.
Distant cells render as merged proxy meshes via HLOD until they stream in sharp. Multiple editors can work in the same world at once thanks to One File Per Actor, which stores each actor in its own file and sidesteps lock conflicts.