In one dimension, there is only one way of packing, that is keeping the balls next to each other.
In two dimension, we can keep a line of spheres on top of another line directly or we can keep the second line in the cavities of the first line.
In my book, for three dimensional packing, only structure is shown when keeping the square packing layers on top of each other:
Would it be possible to get another form of 3D packing from square close packing in two dimensions by making the spheres go into cavities? (similar to the way we kept the line in a staggered way to get hexagonal close packing)
Similarly for packing 2D hexagonal packed spheres in 3D, could we keep the spheres on top of each layer on top of each other( in axis of 3-D packing)?