Background reading (different mods, but intro to the same/similar concepts):

Garrys mod: How to create Bodygroups for Models by The Devils Own

Source Filmmaker (SFM): [MMD to SFM] How to create bodygroups (using Blender) by Dusk

Underhell mod for Half-Life 2: BODYGROUPS by Mxthe

Spike: fte refers to bodygroups as geomsets, and allows you to change them via . . . → Read More