Unreal Engine World Partition and HLOD: A Setup Guide for Large Scenes

What will you learn in this guide?

In a large outdoor scene, you need to preserve detail near the camera while keeping distant mountains, trees, and structures visible. In Unreal Engine, World Partition divides the world into cells and loads or unloads content based on the locations of streaming sources. HLOD (Hierarchical Level of Detail) can represent content from cells that are not currently loaded using proxy meshes.

This guide covers the options for creating a World Partition-ready Level or converting an existing one, creating an HLOD Layer, and generating HLODs. The goal is to prepare a large architectural environment or visualization scene for more manageable streaming. The documentation does not specify a particular Unreal Engine version, so these steps are not tied to a specific version number.

Requirements and getting started

The source documentation does not list any mandatory software, account type, or hardware requirements beyond Unreal Engine. It describes three ways to use World Partition in a project: create a project from a template in the Games category, select an Open World Level, or convert an existing Level.

The most direct starting point is an Open World map. In Unreal Engine, go to File > New Level, select the Open World map type, and click Create. This template enables World Partition, One File Per Actor, Data Layers, and HLOD by default. The sample map also includes a 2 km x 2 km Landscape and an outdoor lighting setup.

If you are working with an existing Level, you can convert it using Tools > Convert Level. The official documentation also describes using the World Partition Convert Commandlet from the command line. If you need to preserve the original Level before conversion, the -ConversionSuffix option can append the _WP suffix to the converted map. -ReportOnly reports the potential conversion without carrying it out. Choose an appropriate conversion method before using these options on your project.

1. Understand how World Partition streams content

World Partition stores the world in a single persistent Level file and divides the area into cells. Cells are loaded or unloaded based on the locations of streaming sources, such as the Player Controller, and runtime grid settings. This means the entire scene does not need to be loaded at once; only the parts needed at a given time are processed.

Whether an Actor is spatially loaded is controlled by the Is Spatially Loaded setting in the World Partition section of the Details panel. When enabled, the Actor loads when it enters the range of a streaming source; when disabled, it loads unless it belongs to a disabled Data Layer. Runtime grid settings, including cell size and loading range, are found under World Partition Setup in the World Settings panel.

Although it is possible to use multiple runtime grids, the official documentation notes that multiple grids can negatively affect performance. A cautious approach is to start with the default 2D Runtime Hash grid and avoid adding more grids before there is a clear need. The sources do not give a single correct value for grid cell size or loading distance; evaluate these in relation to the scene scale and intended visibility.

2. Create an HLOD Layer and choose its type

HLOD settings are managed through an HLOD Layer asset. Open the Content Drawer, go to + Add > Miscellaneous > HLOD Layer, and create the asset. Double-click the new asset to open its settings. A project can use multiple HLOD Layers, allowing you to assign separate layers to different groups of Actors.

Choose the layer type based on the content:

• Instancing: Represents static meshes with Instanced Static Mesh components that use the lowest level of detail. The documentation gives imposters for trees and plants as examples of this type.

• Merged Mesh: Combines static meshes into a single proxy mesh.

• Simplified Mesh: Combines meshes and applies simplification.

The layer settings include Always Loaded, Cell Size, and Loading Range. Note that when Always Loaded is enabled, Cell Size and Loading Range cannot be used. Depending on whether you choose Merged Mesh or Simplified Mesh, additional merge or proxy settings are also available.

3. Assign Actors to a layer and generate HLODs

Before generating HLODs, assign the relevant Actors to an HLOD Layer. The documentation lists three ways to do this: use the HLOD property in an Actor’s Details panel, set Default HLOD Layer on a Data Layer, or use the default HLOD Layer in World Settings.

Set the Mobility of Actors assigned to the layer to Static. Then start generating HLODs through Build > Build HLODs. Alternatively, you can use the WorldPartitionHLODsBuilder commandlet, as specified in the official documentation. Once HLOD generation is complete, content in unloaded cells can be represented by HLOD proxies. The goals of the HLOD system include keeping distant content visible and reducing the number of draw calls per frame.

Common mistakes

A common mistake is assuming HLODs will be applied to the scene automatically. Actors must be assigned to an HLOD Layer, set to Static, and HLOD generation must be run separately. If any of these conditions is missing, the expected proxy output may not be created.

Another mistake is choosing layer types without considering how the content differs. Instancing is documented as an option for plant clusters, while Merged Mesh and Simplified Mesh offer different merging behavior. In particular, Merge Distance in Simplified Mesh settings can close gaps in distant geometry, such as doors or windows. Check the simplified output at different distances in the scene.

Finally, do not apply the same recipe to the entire scene without checking lightmap UVs, material merging, and mesh simplification settings. The documentation notes that some merging conditions can cause visual artifacts. Since the sources do not provide quality or performance values that apply to every project, it is safer to try different HLOD types on representative parts of the scene and inspect the results.

Next steps for architectural and archviz workflows

World Partition and HLOD can be considered for architectural scenes with extensive environmental context—for example, projects where distant terrain, vegetation, or groups of buildings share the same world. Organizing near-field architectural geometry and distant environments into different HLOD Layers can help you manage visual priorities separately. This workflow suggestion is based on the layer and representation methods described in the source documentation; it does not guarantee a specific performance improvement.

First, check the layer type, cell behavior, and HLOD output in a small section of the scene. Before applying the setup to the entire scene, inspect door and window openings, lightmaps, and material appearance. Because the documentation does not specify hardware requirements or licensing terms, the Unreal Engine installation and working environment used by the project team should also be verified before production.

Sources and licensing

This tutorial has been adapted into Turkish from Epic Games’ official World Partition and World Partition – Hierarchical Level of Detail (HLOD) documentation. Both sources are listed as license=free in the provided source list.