>>10
If you want infinite graphical complexity you have to generate the data procedurally, and voxels store the most data(they're basically 3D bitmaps) compared to polygons(geometry defined with filled vectors) which require much more than raw vectors(used in old games like Elite).
i.e. using voxels is the worst choice for complexity, meshes and polygons also require a fair bit of memory,
but procedurally generated objects can be as complex as design of an algorithm creating them, and they can be discarded and regenerated as often as desired(typically they're cached for reuse).