depth buffer test / occlusion culling?

I just wonder how this method is different from doing the depth
buffer testing. As from my understanding, they are the same in the way that
they both will stop rendering polygons hidden by other objects from the point
of view. If so, why was occlusion culling development? Maybe I misunderstand
some mechanism behind. Could anyone explain this for me?

Hi !

Occlusion culling usually works on object resolution, if an object is hidden behind another object we don’t need to render it and can skip it.

Removing occlusion culling will not make any difference to the result, but it may render slower without occlusion culling.

The idea is to minimize the amount of data you send to the OpenGL pipeline, the less data you give to OpenGL the faster it will render.

The depth testing is still used because this works on a pixel by pixel resolution and will take care of objects the overlaps each other to some extent.