Unreal Engine 5 (shortened to UE5) introduced the World Partition feature to speed up working on large environments. In this article, we will explore why it makes sense to use World Partition. We will also compare the experience of working with World Partition in UE5 to working with level streaming in UE4.
World Partition is a tool for building open-world games, where we only want to load a fraction of the level to save memory. Besides that, it also has other benefits.
World Partition provides better tools to handle large environments efficiently. It allows developers to load only the necessary assets, ensuring a smooth experience in the editor. It is also easier to manage instancing of actors and assets in general than it was in UE4.
World Partition greatly improves team collaboration by eliminating the need to lock the entire map. Multiple team members can work on different areas of the map simultaneously.
This is important when using Source Control. With World Partition, game versions become smaller as only the changed assets and not the whole map file need to be uploaded.
In UE5, new levels are World Partition-enabled by default, but we have the option to disable it if desired. It’s not compatible with level streaming. However, it is highly recommended to utilize it even if you are not building an open-world game.
The runtime loading and unloading works great out of the box and replaces level streaming. World Partition also introduces Data Layers, giving us more control over loading and unloading actors. It’s an alternative to the previous layer system.
The World Partition editor provides greater control over what gets loaded by visualizing actors within the map.
UE5 also introduced one-file-per-actor which changes the way how data is stored in the project.
Instead of storing the entire content within the .umap file, UE5 stores actor data in small external .uasset files. For example, when moving a tree within a level, the modification is not stored in the .umap file itself. Instead, it is stored in the .uasset file that is placed in your project directory.
This accelerates development. With the one-file-per-actor approach, you no longer need to lock the entire map. Multiple team members can work on the same map concurrently.
Submissions to Source Control are lighter. Committing changes to source control only involves the small actor files, making repositories lighter and reducing storage requirements.
Actor files are hashed and a black box in Windows Explorer. They don’t show up in UE’s asset browser. Please don’t try to edit them.
Go to "Tools" and select "Convert" in UE5.
The conversion process creates a new .umap file along with external actor files.
Open the converted map and load the regions as needed.
If you created a new level in UE5, it will be set to World Partition via default. If you open up a converted level from UE4, you will be wondering why it is suddenly empty. That’s because you have to tell UE which part of the level it should load.
Open the World Partition editor and enable the "Show Actors" option to visualize actors within the map.
Zoom in to inspect actors in detail.
Select specific regions and load or unload assets as required.
Place new actors or move existing ones within the map.
Note that the asterisk (*) indicating unsaved changes appears on individual actors rather than the entire map.
Save the changes, which will result in multiple files being saved.
We will use Git with Anchorpoint here, but this works with any source control provider.
Open your source control application and take a look at your changed files (or change list).
Add a meaningful message describing the changes and push the commit.
Since only small actor files are uploaded, the commit process is pretty fast. It’s a few KBs instead of hundreds of MBs.
World Partition offers better tools for working on large environments, improves team collaboration by allowing parallel work on maps, reduces project sizes, and replaces level streaming with more control over loading and unloading assets. The one-file-per-actor approach keeps repositories lighter and avoids locking while level files. You can convert your existing maps to World Partition with an integrated utility. Submitting changes via source control is faster, and you have more control over editor performance and level streaming.
Data Layers are a replacement for Layers in UE4 and help you to manage when actors should be loaded or unloaded. They help you to manage complex levels with a lot of assets. You can control them via Blueprints and have options like visibility, etc.
Hierarchical Levels of Detail (HLOD) are used to manage static mesh actors that are visible from a long distance of the viewer. They combine these actors to a single proxy which helps to reduce draw calls and increases performance.
In UE5, every new level has World Partition enabled by default. When you want to convert an existing map to World Partition, use the conversion utility which can be found under “Tools/ Convert Level…”. This will create a copy of the map with World Partition enabled.
First of all, go to the World Settings (Window / World Settings) and disable the checkbox “Enable Streaming”, which can be found in the section “World Partition Setup”. After that, open the “Advanced” section and click on “Disable World Partition”. Keep in mind that this will clear your scene.
A better way to do this is creating a new level from the “Basic” template.
World Composition is a feature that was introduced in 2015 for optimizing huge levels for performance. Unfortunately, it’s a pretty tedious system and requires a lot of work to create proxy meshes. It is a pretty outdated system, which is not available in UE5 anymore. It has been replaced by World Partition.
