[ODE] visibility detemination?

[gl]

> I gave it a cursory look recently.  AFAICT from a quick terrified
> glance it's similar to an octree (didn't notice whether each
> subresolution is offset -- I don't think it is, which might be an
> opportunity for future optimization) but its sparse cells are hashed
> by location and resolution instead of being kept in a strict
> hierarchy, so there's little need to walk up and down recursively
> or know the realistic extents of the tree (neat).

Interesting, thanks.
--
gl