So Nanite is just traditional LOD baking implemented in a wholistic and automatic way?
The major difference seems to be they've done the work end to end to handle all the occlusion corner cases as well as a sophisticated mesh and texture streaming implementation that targets modern SSDs.
It's not traditional LOD baking. There's no LOD baking. It's the new rasterization system doing the whole work.
And most of us doesn't use fast SSDs like in PS5 and it works really well. Also these engineers said, it even works just fine with slowers HDDs too. Because, they don't stream meshes for each camera movements. But it's a continuos setup.
I’m not an expert on this, but there seems to be a custom GPU renderer optimized for dense triangle meshes, with its own occlusion pass. The LOD is also calculated based on clusters, multiple per-mesh with way to fix seams between cluster at different levels. This works best with very dense meshes such as those from photogrammetry or zbrush sculpted.
The major difference seems to be they've done the work end to end to handle all the occlusion corner cases as well as a sophisticated mesh and texture streaming implementation that targets modern SSDs.