[Jasper_]

That's known as "occlusion culling", and it's still a bit of an open problem [0]; a lot of games do indeed just send all draw calls inside the frustum. Turns out a good Z-prepass is pretty free and helps a lot with things occlusion culling would normally help with. And deferred rendering helps even more with things like quad overdraw from disparate objects, as long as your material mask is mostly the smae.

The Source Engine still uses has a pre-built BSP for surface visibility. Source 2 has replaced this with a world-aligned visibility octree [1].

[0] The common solution these days is a low-resolution depth buffer rasterized on the CPU with SIMD, because doing it on the GPU would have noticeable latency... you've probably played a game where you turn into a twisty hallway and the walls/object in there only show up after a few frames... that's GPU occlusion culling at work.

[1] https://developer.valvesoftware.com/wiki/Half-Life:_Alyx_Wor...