rigging


Stop Staring“, by Jason Osipa, is a book about modelling, rigging and animating the face.  It’s especially geared towards rigging, and offers several techniques to reduce (or automate) the number of morph shapes needed for facial animation.

I’ve been working through the book myself; though I don’t yet have a final rig, I have seen rigs completed by other people based off this book, and they seem really cool.

The book also introduces a more practical approach to lip-syncing, based on “visemes,” which is where speech is broken down to it’s visible mouth-movement components, rather then it’s phonetic structure.

You can read more about it in this more in-depth review.

Vector IK is a great technique for some situations where normal IK just doesn’t cut it.  The technique basically uses one control to rotate and “curl” an IK chain.  It’s also fairly simple to do.

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My first real introduction to rigging was Javier Salson’a reverse-footlock tutorial.  It’s an interesting technique that results in a fairly easy-to-use foot rig.  What was significant about this tutorial is it introduced me to the idea of using an ik pole vec constraint to control where knees and elbows point.  With this tutorial, I produced my first actually usable rig (a simple carrot, that I animated my first walk cycle on).

I’m not sure if reverse footlock is the best foot rig or not.  Certainly I’ve learned a lot since first being reading this tutorial.  But this is still where I really started to understand rigging for the first time.

A while back someone wrote a siggraph paper on using dual quaternions for a more advanced skinning.  Unlike linear skinning, dual quarternions don’t suffer from the “shrinkage” problems and require far less corrective shape keys as a consequence.

I’ve used this in my own rig, and it seems to work great.  It’s implemented in Blender, and the site has links to plugins for Maya and XNA.

So, here’s my first post: Shoulder Deformation.

contrast between without and with good deformation

This is actually a topic I’ve spent a great deal of time on.  My theory for the main problem with shoulder deformation is twofold: a) people don’t realize you can’t lift your arm above your shoulder, going higher requires rotating your shoulder itself, and b) they don’t build support for twisting into their upper arm rig.

You can test both aspects of this theory yourself.  Try lifting your arm above your head without moving your shoulder.  And try twisting your upper arm and see what happens.  The upper arm twists, it doesn’t rotate in a block.  Trying to blend between the upper arm and the shoulder with weights won’t help either, a true volume-preserving twisting rig is needed.

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