Games Design Fundamentals - Game Engines: Culling

Frustum culling is where whatever's within the distance of the virtual camera in the scene is rendered. Anything outside the camera's distance is culled and not acknowledged by the renderer.

Level of Detail culling is based on the distance between the game asset being rendered and the virtual camera in the scene. Assets a certain threshold away will render with either a lower, more optimized poly count, a lower quality material with removed detail maps or both. Some games change the 3D model for 2D sprites that rotate in accordance with the camera once they get so far away.

Backface culling is when the yonder side of a game asset that cannot be seen by the virtual camera isn't acknowledged in the render, allowing more processing power to be dedicated to higher quality game assets that dominate the foreground.

Portal culling is how the virtual camera established what's been obscured by game assets in the foreground (eg. windows, doorways, portals, etc) and culls the hidden assets behind.

Occlusion culling is very much similar to frustum culling where everything in range of the camera is rendered except everything out of view or obscured by game assets in the foreground isn't acknowledged by the renderer.