Face Gen is not available for Mac but there are plenty of alternatives that runs on macOS with similar functionality. The best Mac alternative is Blender, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 25 alternatives to Face Gen and 14 are available for Mac so hopefully you can find a suitable replacement. Other interesting Mac alternatives to Face Gen are MakeHuman (Free, Open Source), ZBrush (Paid), VRoid Studio (Free) and MODO (Paid).
MakeHuman is an interactive modelling tool for creating realistic 3D human characters. These models can be exported to several computer graphics and animation platforms including Blender, Unity 3D, Unreal Engine, OpenSim and Second Life.
pixiv has released "VRoid Studio", a character maker that allows users to create, in easy steps, 3D model characters which can be used in various VR\AR platforms as well as the production 3DCG animation and games.
Dead Deer is a 3D modeler, 3D game maker, and a 3D demo maker designed to create games. The scripting language allows you to code interactions in pseudo-C with the animation and synthesizes your rendering with your shaders.