Occlusion Culling (Occlusion Culling) is a technical term that is extremely important in the rendering and optimization of game graphics (technical art). A powerful optimization technique that automatically skips the rendering of 3D objects that are in view but hidden behind foreground walls or buildings and are not visible to the player.
Real world analogy: An order to completely skip makeup on the furniture on the other side of the "closed door" of the room
Occclusion culling is "an order to completely skip bringing in furniture or decorating a separate room behind a closed door (a huge wall)". In frustration culling (visual field culling), as long as you are facing the direction of the door, behind-the-scenes efforts are made to render invisible chests and beds behind the door as ``something''. Occlusion determines that ``If the door is closed, you can never see what's behind it, so there's no need to draw it at all'' and wipes out the rendering load of all the assets behind it with just the cost of drawing one door.
Illustration: Occlusion Culling (Infographic that clearly illustrates the basic processing flow and mechanism of occlusion culling) in Japanese.
Detailed mechanism and operating principle
Set the "Occlusion Static" mark on static objects on the scene, and Bake the occlusion data (portal cell structure) from the Culling window in advance and do the occlusion culling at runtime.