Hierarchical Level of Detail Overview

HLODs, in their simplest form, combine pre-existing Static Mesh Actors into a single Static Mesh Actor and material, with atlased textures, to reduce draw calls which in-turn helps with your performance of your game. There is a robust system that enables you to set what needs to be generated when you create these HLOD Actors.

Proxy Meshes

Once your proxy meshes have been generated, you can find them located under the HLOD folder generated in your project. This will include the LODActors referenced in the HLOD Outliner.

image alt text

These proxy meshes can be opened independently and settings adjusted.

image alt text

The proxy mesh above contains several different elements that originally all had their own textures that have now been combined into a single texture.

This can be problematic for anything using Mask or Opacity. These alpha channels are not passed to these assets for this merged texture. If opacity or masked items are needed you would want to consider unchecking the option for Merge Textures. When doing this the Proxy Mesh will assign the original material as a Material Element ID instead of combining.

image alt text

HLOD Volume

The HLOD Volume is used to manually define/create a HLOD cluster. This volume can be added from the Modes panel Place Mode and dragged into your level.

image alt text

Place this volume around Actors you want to be grouped into the same cluster. It can be helpful to make this slightly larger than the Actors and should not be tightly bounding them. Once you have placed the volume around the Actors you can use the option Generate Clusters from the HLOD Outliner to create a new cluster with these grouped Actors.


Below is an example of Generated Clusters before and after adding HLOD Volume.

image alt text

HLOD Level Desired Bound Radius: 500

image alt text

Drag in the Volume and scale accordingly to cover your Actors.

image alt text

Selecting the generated LODActor from the HLOD Outliner shows the cluster created and the Cluster bounds.

Right-click on the LODActor in the HLOD Outliner and click on Select Contained Actors to see the Actors used for this particular LODActor in your scene.

image alt text image alt text

Details Panel for LODActor

By selecting a LODActor in the level you have access to some settings in the Details panel to override some aspects of your generated HLOD along with details to which static meshes have been included with this cluster. This is not unlike any other Actors in your scene where you have the option to override or change some values to work within the confines of your design.

image alt text