Add support for BlenRig

[joepal1976]

BlenRig is a rigging system used, for example, in some blender movies. It solves somewhat similar use cases as Rigify. It should be possible to add support for BlenRig in MPFB in a way which is similar to how Rigify is supported.

BlenRig's github repo is here: https://github.com/jpbouza/BlenRig

[Vidyut]

I'm not much of a coder (I'm a champion copy-paster), but I'd be happy to test anything needed.

[joepal1976]

Having looked into this a bit, there are good news and bad news.

The good news is that it should be possible to turn pretty much the entire first part of the guide (the 55 step reproportion) into a one-click autofit button for an MPFB character. It'd take some work to achieve this, but it's not rocket science. It can be built on technology already implemented for other rig types.

The bad news is that blenrig seem to have different ideas about the composition of a character. An MPFB character is composed of entire body + control surfaces as one single mesh, with eyes, eyebrows, eyelashes, tongue and teeth as separate child objects. BlenRig seem to presuppose that the both the head and the hands are separate meshes too. This might be a misunderstanding on my part since I'm unfamiliar with blenrig. However, if this is the case some extra magic would be needed in order to amputate the body mesh. Also, a new solution would need to be found in order to not break clothes and hair fitting. This is probably not impossible, but it makes things a lot harder.

[Vidyut]

I mentioned this to the guy who made BlenRig and he thinks it would be complicated too.