This is pretty trippy: David OReilly found that a large grid rotating at a certain speed will appear to group itself into smaller grids, rotating independently.
It appears the persistence of vision effect overrides our knowledge that this is a single grid and divides it up optically. This only seems to work on a uniform grid (I also had interesting results with a brick formation), but the effect is lost when using a checkered texture.
Wow, that's a weird effect.
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