What is Level of detail (LOD)?
Level of detail (LOD) is a technique that swaps a model for progressively simpler versions as it gets farther from the camera, saving performance where the difference can't be seen.
A tree 200 metres away covers a few dozen pixels on screen. Drawing all 50,000 of its triangles there is wasted work. With LODs, the engine automatically switches to a 5,000-triangle version, then a 500-triangle one, and maybe a flat billboard in the far distance.
A typical LOD chain
- LOD0: full detail, used up close
- LOD1: about 50% of the triangles
- LOD2: about 25%
- LOD3: about 10%, or an impostor billboard
The percentages vary by project. The aim is that no one notices the switch.
Making LODs
Unity and Unreal can generate LODs automatically, and Blender's Decimate modifier produces them by hand. Generated models with dense, uneven meshes usually decimate well, since there's no careful topology to protect.
Related techniques
Unreal Engine's Nanite virtualised geometry handles much of this automatically for supported meshes. For the web, the main lever is still download size. See Draco compression and polygon count.
Written with AI assistance and reviewed by the Renderlyst team. Corrections welcome at alishbakhalid766@gmail.com.