LODs Explained: Level of Detail for Better Game Performance

A tree that fills the screen when the player stands next to it might need thousands of triangles to look good. The same tree on a distant hill covers a few dozen pixels; rendering all that detail there is wasted work. Level of detail (LOD) systems solve this by switching objects to simpler versions as they get further from the camera.

How LOD works

An artist or tool creates several versions of a model:

• LOD0: the full-detail model, used up close.
• LOD1, LOD2, LOD3...: progressively simpler versions with fewer triangles and sometimes simpler materials.

The engine chooses which version to draw based on the object's distance or, more commonly, how much of the screen it covers. Fewer triangles and simpler materials for distant objects reduce GPU workload, which helps frame rate, especially on mobile and in large scenes.

How many levels?

It depends on the object and the game. A common pattern is three or four LODs, with each level using roughly half the triangles of the previous one, or fewer. Large, frequently seen objects such as buildings, vehicles and vegetation benefit most. Small props that are never seen from far away may not need LODs at all.

Setting transition points

Transitions should happen when the change is not noticeable. Test in the actual game at the real camera angles and resolutions. Things to check:

• Silhouette: the outline of an object matters most at a distance. Preserve it when simplifying.
• Popping: a visible jump when switching LODs. Smoother transitions, such as dithered cross-fades available in many engines, help hide it.
• Shading and normals: large shading changes between levels are more noticeable than lost geometry.

Beyond meshes

• Material LODs: switch to cheaper shaders or remove expensive effects at distance.
• Texture mipmaps: engines automatically use smaller versions of textures at a distance; make sure mipmaps are enabled.
• Impostors and billboards: very distant objects, such as forests, can be replaced with flat images rendered from several angles.
• Culling: objects that are tiny or hidden can be skipped entirely with distance and occlusion culling.

Creating LODs

Most 3D packages and game engines include automatic mesh simplification that can generate LODs, which works well for many organic objects. Hard-surface models with important edges often benefit from manual cleanup. Keep UVs consistent between levels so textures still line up.

Some modern engines offer alternative approaches. Unreal Engine's Nanite virtualised geometry, for instance, handles detail for supported meshes automatically, although traditional LODs are still relevant for other cases and other engines. Check what your engine recommends.

Plan budgets early

Define triangle budgets per asset type and LOD level in your art guidelines, ideally in your game design document. Retrofitting LODs at the end of a project is far more work than planning them from the start.

Measure, do not guess

Use your engine's profiler to see whether geometry is actually the bottleneck. Sometimes the real cost is draw calls, overdraw or shaders. For draw calls, see our guide to texture atlases and draw calls.