from what I remember from when ive made selection sods is that there actually quite basic depending on what program your using to make sods (milkshape or 3dmax) all you really need is a mesh that goes around the selected object, a texture and the basic joint/node hierarchy.
i also believe shields are done in a similar way (if using 3dmax you can add texture animation but not sure if it works in milkshape)
