Were you ever able to work out how to form something like retna using HTMs? The location factor of the semantic folding process I could never recreate efficiently myself (“snip-its are distributed over a two dimensional grid in such a way that snip-its with similar meaning are placed close to one another”). Because of this, the word SDRs that I am able to create encode semantics properly, but lack topology.
(BTW, reading the papers now)