Occlusion Culling
Skip rendering hidden geometry
Also known as: Occlusion query · Visibility culling
Definition
Occlusion culling skips rendering meshes that are hidden behind other geometry from the camera's perspective. The engine maintains a visibility map at runtime (UE5 uses hierarchical Z-buffer occlusion); meshes determined to be fully behind opaque geometry are skipped entirely. Crucial for indoor/corridor games where most of a scene is technically loaded but not visible at any moment.
In production
UE5 occlusion culling is automatic and relies on a hierarchical Z-buffer test performed each frame against the camera's depth buffer, but its effectiveness depends entirely on having large occluder surfaces — walls, terrain, building facades — that actually block substantial geometry behind them. Tiny meshes don't occlude anything meaningful even though they technically sit in front of the camera; only big, contiguous opaque surfaces like floors and walls generate useful occlusion. Level designers building corridor-based or interior levels get the biggest wins because most of the map sits behind a handful of walls at any given moment, whereas open-world scenes see far less benefit and lean more on distance culling and LODs instead. A known pitfall is foliage or glass treated as occluders — since they're not fully opaque, UE5 correctly refuses to use them for occlusion, so a "solid-looking" hedge doesn't cull anything behind it.