usually it's the same as number of materials for that mesh
there is also functions to getattributetable, that can tell you exactly what amounts of subsets mesh has and for what vertices each subset is set
Crazy dude smoking D3D11, AngelScript, PhysX, 3D Sound, Network, DB, FBX, and some other weird things, doing that on Visual Studio 2010 + Visual Assist X on Overclocked CPU
