UEFN HLODs, Data Layers, Draw Distance, and Static Level Optimizations | Unreal Fest Orlando 2025

Summary

In his Unreal Fest session, GameDev Micah explains how to reduce rendering and gameplay workload in UEFN by following the principle “less is best”: remove unnecessary data, components, and instructions so the server and clients have less work to do. The presentation focuses on optimizing static levels and uses Unreal Engine concepts to explain behavior that is less visible in the UEFN editor.

Core Concepts

Draw Calls and Instancing

A draw call is a request from the CPU for the GPU to render a component. Repeated objects can generate many calls, while Instanced Static Meshes (ISMs) batch copies of the same mesh and typically reduce draw calls. ISMs work best for objects whose instances do not need to be changed individually at runtime; using one for a mesh that appears only once may be inefficient.

HLODs and World Partition

HLODs replace distant actors with simplified representations, reducing the amount of scene detail that needs to be rendered. World Partition can generate HLODs using merged meshes or instancing. Cell size matters: larger cells can consolidate more objects, while smaller cells produce more separate components and data.

Spatial Loading and Data Layers

Spatial loading can reduce what is loaded on a client, but it does not by itself remove actors and devices from the server’s workload. Data Layers can unload actors on the server as well, making them useful for areas or events that do not need to remain active.

Draw Distance and Culling

Maximum draw distance can prevent distant objects from being considered for rendering, helping reduce GPU work. However, Micah warns that Live Edit may reset draw-distance settings.

Static and Movable Objects

Mark objects as static when they will not change during play. Movable objects may require additional checks, such as whether they have moved, and can incur more server, network, or physics work.

Disable features an object does not need, including damage, overlap events, collision, sound, shadows, and other processing options.

Nanite and Mesh Detail

Micah notes that Nanite is not a general solution for UEFN mobile targets, which do not support it in the scenario discussed. He also explains that multiple LODs can improve rendering at a distance but add stored mesh and material data.

HLOD Package-Size Trade-offs

HLODs can improve runtime rendering but increase project size because generated meshes and related data are included in the package. In the Tilted Towers example, the presenter reports a base folder size of about 46.7 MB, with default HLODs adding roughly 22 MB.

In a larger test, instanced representations added substantially less size than merged meshes. Voxel-simplified HLODs reduced data further, though visual quality could suffer.

Textures, Materials, and Other Tactics

Reuse materials and textures, reduce texture resolution where appropriate, and pack texture information into channels rather than storing several separate textures. Simpler material graphs and fewer triangles reduce the data and shader work that must be processed.

Other tactics include:

• Use larger props where they can replace many small pieces.
• Merge meshes used only in one place.
• Remove unused components and asset references.
• Use the Bulk Property Matrix to change settings across many similar actors.
• Use Verse pooling to reuse a smaller set of devices by moving them between locations instead of placing many equivalent devices across a map.

Performance Analysis and Practical Guidance

The talk uses an Unreal Insights example with 20,000 actors to illustrate how mobility and representation affect workload. The presenter reports that changing movable objects to static allows automatic dynamic instancing to reduce draw calls, while HLODs can further reduce the number of individual objects the engine must consider. A manually consolidated ISM can be even lighter when the objects are suitable for instancing. These demonstrations illustrate the principle; they do not guarantee the same results in every island.

Micah also distinguishes the workloads involved in a Fortnite experience: the server processes gameplay and sends network updates, while each client performs its own rendering. Reducing unnecessary actors and features can therefore help both gameplay processing and client rendering, but client-side spatial loading alone does not eliminate server-side work.

Guides and Resources

Micah says the slides are available through his link and points viewers to his GameDev Micah YouTube channel, where he has longer editor walkthroughs explaining individual settings.

He also recommends:

• James and Julian’s UEFN management material and a project-optimization video.
• How to Boss for a Data Layers tutorial.
• Clever Like for additional tutorials.

Main Speaker and Sources

• Main speaker: GameDev Micah, presenting the optimization guidance and Unreal Insights examples.
• Additional resources recommended: James and Julian, How to Boss, and Clever Like.