Unreal Engine World Partition HLOD: Optimize Large Scenes Step by Step

What will you learn in this guide?

When preparing a large outdoor area, campus, or building complex in Unreal Engine, not every object needs to remain visible in full detail. For distant models that do not require interaction, HLOD (Hierarchical Level of Detail) lets you represent a group of Static Mesh Actors with a simpler proxy. Used with World Partition, this approach also helps represent the environment in cells that are not currently loaded.

This guide covers the relationship between World Partition and HLOD, how to set up an HLOD Layer, choose an appropriate layer type, assign Actors, and generate HLODs. It also explains why material, opening, and distance checks matter in architectural visualization. Epic Games documentation notes that HLOD can reduce draw calls; the result should therefore be treated as an optimization method to test in your scene, not as an automatic performance guarantee.

Requirements and preparation

This workflow requires a Level and the use of World Partition in Unreal Engine. The source documentation does not specify a particular engine version, account type, price, or minimum hardware requirements. The suitability of your project version and workstation should therefore be verified separately in your production environment.

World Partition can be used when creating a new Level by choosing the Open World type; existing Levels can also be converted. The documentation describes using the option in the Tools menu or the World Partition Convert Commandlet. When converting via the command line, the -ConversionSuffix option can add the _WP suffix to the converted map for testing. To understand how conversion affects project files, a cautious approach is to start with a test map.

As part of your preparation, identify the objects to include in HLOD. Distant environment buildings, trees, and terrain pieces may be suitable candidates; separately inspect the proxy result for facades, furniture, or details that need to remain legible in close-up views. Some material properties may not be preserved as expected during merging. The source documentation specifically notes that, for masked content or content using opacity, alpha channels are not transferred to the merged texture.

Creating and configuring an HLOD Layer

1. Create the Layer asset. Open the asset creation menu in the Content Drawer and select HLOD Layer under the Miscellaneous category. After creating the asset, open it in the Asset Editor to edit its properties. A project can use multiple HLOD Layers to meet the needs of different content groups.

2. Choose the layer type to suit the scene content. Instancing represents source Static Meshes with Instanced Static Mesh components; the documentation describes this type as suitable for imposter use cases such as trees and foliage. Merged Mesh combines multiple Static Meshes into a single proxy mesh. Simplified Mesh also simplifies the geometry in addition to merging it. When choosing a type for an architectural project, compare the scene’s distant appearance against the required level of detail.

3. Review loading behavior. Layer settings include Always Loaded, Cell Size, and Loading Range. Always Loaded keeps the relevant proxy loaded at all times; when this option is used, the Cell Size and Loading Range settings are unavailable. When Merged Mesh or Simplified Mesh is selected, you can also adjust merge or proxy settings specific to that type.

4. Choose merge settings as needed. For Merged Mesh, options are available to generate lightmap UVs, merge materials, and specify output UV channels. Settings are also provided for selecting the LOD level to use. The Simplified Mesh section includes controls such as screen size, mesh merge distance, normal calculation method, and lightmap resolution. Not every option needs to be enabled; decide based on its visible effect on the target image.

5. Assign Actors to the HLOD Layer. You can make the assignment through the Actor’s HLOD property in the Details panel. You can also use the default HLOD Layer setting in a Data Layer or under World Settings. To generate World Partition HLODs, Actors must be assigned to an HLOD Layer and have their Mobility set to Static.

6. Generate HLODs. Run Build > Build HLODs in the editor. Alternatively, you can use the WorldPartitionHLODsBuilder commandlet described in the documentation. When generation is complete, inspect distant camera angles and check whether the proxy meshes preserve the legibility of the environment.

7. Inspect the view and clusters. You can view HLODs using the LOD color visualization options in the View Mode menu in the viewport. The HLOD overview documentation also describes manually clustering Actors with an HLOD Volume and generating clusters through the HLOD Outliner. Evaluate how this approach fits your World Partition project; do not assume that the workflows in the two documents use the same settings.

Using HLOD in architectural and archviz workflows

HLOD is worth considering for teams looking to organize the representation of distant buildings and foliage in architectural scenes with expansive surroundings. For example, you can preserve a close-up view of the main building while representing more distant environment models with proxies. According to Epic Games, HLOD proxies can help reduce draw calls by using merged representations instead of separate Static Mesh Actors. Since the actual gains depend on the scene and settings, do not assume a performance improvement without measuring and comparing the results visually.

In interior scenes, HLOD is generally most relevant to areas such as the exterior environment visible through windows or distant buildings within a large complex. The loss of detail in a proxy may be unacceptable for close-up furniture and surfaces. Merge Distance in Simplified Mesh can merge geometry in a way that closes openings such as doors and windows in distant geometry. Check the alpha behavior of masked materials and materials using opacity, too. For this reason, evaluate the result not only in the editor viewport but also at the camera distances and angles used for delivery.

Common mistakes and next steps

Assuming that HLOD will keep every object looking the same as its nearby source model can lead to incorrect assessments. The proxy’s appearance varies according to the chosen layer and settings. Before generation, check Actor assignments and confirm that Mobility is set to Static. Also review how the mesh merge distance affects doors, windows, and other openings.

Another point to watch is the geometry sampling interval in Simplified Mesh settings. The source documentation warns that sampling large geometry too densely can significantly increase memory requirements. Test the settings on a representative group before applying them across the entire scene. If you use material merging, separately check the texture results for masked surfaces and those with opacity.

As a next step, compare the results of Instancing, Merged Mesh, and Simplified Mesh across different environment groups. For clusters that look problematic, review Actor assignments, layer settings, and the appearance at actual camera distances. If you need to convert the project to World Partition, first review the conversion options and test-map workflow. Since the sources do not provide specific hardware recommendations or version requirements, verify these separately with your Unreal Engine installation and workstation.

Sources and license

This guide has been adapted into Turkish based on Epic Games documentation about World Partition, World Partition HLOD, and the HLOD overview. The source records list the license status as serbest; since the sources do not specify a named license type, no specific license name is claimed here.