Even Minecraft started with random blocks ...
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Published on ● Video Link: https://www.youtube.com/watch?v=LKxekjZ3J1I
... except what you see as blocks are actually chunks! ;)
16x16x16 voxels/cubes per block/chunk
This demo uses 16 GB of memory when working with it in the Unity Editor! Of course this isn't optimized yet, can easily be cut in half and more.