Backface Culling vs Occlusion Culling — What's the Difference?

Front-/Backface culling is done at the hardware level; the GPU determines the winding order of a triangle (clockwise vs. counter-clockwise relative to the camera). If it's back-facing, the triangle is discarded before the pixel shader runs.

There are cases where you'll need to disable it, for example two-sided materials like foliage cards, thin fabric, or leaves need both faces to be visible, and transparent geometry such as glass often requires interior faces to render correctly, so the volume reads right. Fast, cheap, and on by default for opaque geometry.

Occlusion culling happens at a higher level, before draw calls are even submitted. It determines whether an object is hidden behind something else; if it is, the engine won't queue the draw call at all. This works well for opaque assets.

Alpha-tested and alpha-blended materials are trickier: because they don't fully write to the depth buffer, they can't reliably act as occluders themselves. Some engines handle the occlusion pass automatically with tools like Umbra, or through built-in Software Occlusion Culling like UE. But you can also manually help the engine by creating custom occluder meshes, which is what tomorrow's post covers.

Key difference: backface culling happens at the triangle level and removes back-facing triangles. Occlusion culling happens at the object/draw call level and skips rendering hidden assets entirely.

© 2026 Stefan Groenewoud — All views are my own, not those of my employer.