In godot engine we decide to do a continuous level of detail based a pixel error metric. (simplified explanation pixel-error -> based on fov -> based on floating point error of the meshopt_simplifyWithAttributes function)
That's a cool demo (even if it doesn't work on my phone, I get it from the video), but it's a long, long way from a nanite implementation. At best I'd call it dynamic LODs or something.
- https://github.com/AIFanatic/three-nanite
- https://news.ycombinator.com/item?id=42974461
three-nanite is based on https://github.com/zeux/meshoptimizer cutting each mesh into maybe 124 triangles per chunk.