Blocks are rendered in the same way as
in a non-fractal block game:
Blocks are rendered by merging adjacent
1x1 squares together to form quads
using the Quad Algorithm
(see here).
This is done in the games Infinifrag 2 and Block Arena.
We differentiate between 1x1 squares that are
external (pointing outside of a chunk)
versus internal
(see here).
We calculate the internal squares and basically
create vertex buffer objects for them
while the chunk is being procedurally generated
(in a worker thread).
On the other hand, the main thread must handle
the external squares.