Trunc is a three-dimensional three-player Hex variant of which I first wrote up a description as an exchange gift for the eighth Gathering for Gardner, in the manuscript If two were three, what would Hex be?. I hope to synopsise the rules here at some point; until then, that manuscript specifies them.
There now exists an implementation of Trunc, written by Alex Fink (myself) and Janek Kozicki, at present in version 0.6.1. The compilation requires libqglviewer, as well as a single file from the boost C++ libraries, which is included. The included makefile is for Janek's Linux system; I modified it thus for my OS X one.
Watch this space: I hope soon to implement the win detection in terms of surfaces and to play around with the display modes more. Many thanks to Janek for the impetus for this project, and his enthusiasm.
Here is a video of a slightly older version of the implementation.