Here's an implementation of the algorithm in Scala: <a href="https://github.com/locationtech/geomesa/blob/master/geomesa-z3/src/main/scala/org/locationtech/geomesa/curve/XZ2SFC.scala" rel="nofollow">https://github.com/locationtech/geomesa/blob/master/geomesa-...</a>
This is from 1999 - which doesn't make it any less interesting, but I'm curious if any new insights have been found in the twenty years since.