Graphical representation of a v6 address space usage

Hi !

I'm trying to put together some statistical data about the allocation
status of a (rather large) IPv6 LIR range. I'm used to representing v4
address space using Hilbert curves, but it's not really optimal for
IPv6 as the allocated space is too sparse, and the unitary allocations
way too small to label them on the graphical representation.

So I'm looking for "graphical representation best practices", such as
an anamorphic scaling algorithm to draw a more readable map while
still pointing out the vast amount of free space remaining with a non
proportionnal surface.

Did anyone see such a tool ?

Thanks !