I am one of the developers of Regina, a suite of mathematical software for
3-manifold topologists. It focuses on the study of 3-manifold triangulations
and normal surfaces. I also maintain the Gentoo packages for Regina.
For official downloads for other distributions, see http://regina.sourceforge.net
Gentoo packages for Regina are available in a layman overlay
Once layman has been installed, you can install the overlay by running
# layman -a regina-gentoo
You will then be able to install Regina with
# emerge regina
that version 9999 of Regina in the overlay will always update to the latest GIT
revision, which may or may not work at any given time.