Bohemia Interactive ARMA 3

Install Steam
Install steam using "emerge games-util/steam-meta", or following the appropriate Gentoo Wiki for installing the Steam client.

GPU Driver Requirements
ARMA 3 requires OpenGL 4, and doesn't appear to be GPU bound due to the various driver implementations.

NVIDIA: "Mesa 11 + latest llvm (maybe even 3.7) should give you opengl 4.1, IIRC." (Since I have an NVIDIA GeForce GTX 670, I've yet to been able to unmask the =media-libs/mesa-11 dependency due to all of the other unmasked dependencies. As such, my work temporarily ceases at this point.  See below Troubleshooting for possible errors pointing to this Mesa dependency.)

AMD: Reported to supposedly just work?

Common Startup Parameters
"-noLogs -nosplash -world=empty -skipIntro" "-window" "-winxp"

Troubleshooting

 * Errors lacking Mesa 11 Version requisite providing OpenGL 4 support: "Game wants to disable DXGI reacting to ...", ...