Hi, here is an ebuild for the demo of Descent 3, courtesy of Loki. The screen stays blank at the default 640x480 fullscreen with nvidia-kernel-1.0.8178-r3 in xorg-x11-7.0, but is OK when windowed.
Created attachment 78133 [details] descent3-demo-1.4.0a.ebuild
I had no such issues (same driver, modular X) with the game when I tested it. Thanks for the ebuild!