You are correct that you can render a small section of a very large data set by re-centering your origin of the data sent to GPU around a small subsection. So,

You are correct that you can render a small section of a very large data set by re-centering your origin of the data sent to GPU around a small subsection. So, now the question becomes "But, do you really want to?" > Overall, we are quite happy with how this solution turned out. We think it is the closest to "just works" that we can get. I think this is the crux of it. The performance penalty is very small and the convenience factor is very high. But, now I want to know what they do with the positions of lights in the scene... Likely transformed to view space regardless for deferred rendering, I'd guess.