I think the key here is that e.g. surface information only grows at O(N²) rate whereas number of grid points scales as O(N³). The hash function approach means y

I think the key here is that e.g. surface information only grows at O(N²) rate whereas number of grid points scales as O(N³). The hash function approach means your arrays will be filled with detailed information densely, whereas sampling coarsely would still leave most of the array with "nothing here" information. Your comment made me realize that I forgot to mention the multi-resolution aspect of their hash encoding (there are several data arrays corresponding to different resolutions - coarse ones are 1:1 indexed but finer ones have hash collisions for the network to deal with). It's in the title, but I should still include it.