Twist Distribution Method

I've been experimenting with twist distribution lately in my rigs to get nice deformation. This is crucial in CG because a rig without good deformation is like a bad drawing. And in CG a bad drawing doesn't even have a childlike charm. It just look like someone put a magnet too close to the computer.

There are a bunch of methods for twist distribution. You can do it with locators, expressions, constraints, or math nodes. One method on Creative Crash got my attention. It uses an IK Handle to prevent one joint from twisting, and then you can apply your twist distribution down the line. Then someone in the comments pointed out a better way to do it using math nodes instead of a locator & constraint. But going back and forth between the comment and tutorial itself can be annoying, and the guy in the comments doesn't include pictures, so I've created a condensed explanation. The original tutorial is here:
http://www.creativecrash.com/maya/tutorials/character/c/advanced-non-flipping-upper-arm-roll

First create a normal IK Chain arm or leg. Then attach the deform chain roll joints to the shoulder or, in the case of a quadruped, to the torso. Apply an RP IK to the first roll joint and zero out the pole vector so it won't twist.
Then create two Multiply/Divide nodes with the operation set to "Multiply" and the 2X value set to -1. Plug rotate x of the bind bone (the one that is part of the twist-distribution system) into the first Multiply/Divide node, on input 1X. Then plug the rotate X of the driver bone into Input 1X on the second Multiply/Divide node.

Then create a Plus/Minus/Average node, set the operation to "Subtract" and attach the bind bone Output X into input 1D[0] and the driver Output X into input 1D[1]. Now attach the output of the Plus/Minus/Average node into a new Multiply/Divide node, into both input 1X and 1Y. Then divide each of those numbers by whatever value you think will create good twist distribution. I chose 3 for Input 2X and 6 for Input 2Y. Then plug Output X into the first bone that will twist, and Output Y into the second bone that will twist. If you have more twist bones, create more Multiply/Divide nodes as needed.

The node network will look like this:

The bones in the viewport look like this:

If anybody reads this and has questions/suggestions, leave a comment. This is far from the only way to do twist distribution, but it's a method I've found to work.

Introduction

Hi! My name is Chris Scott and I animate things, rig stuff, and do all the other elements of CG with varying degrees of skill. I recently graduated from Sheridan College's Digital Character program, and figured I'd start an actual blog instead of just posting random bits on facebook.

So a little about me. I started learning CG a little over 2 years ago now. I graduated from Rutgers University in 2012, after doing a thesis project on T.S Elliot's "The Love Song of J. Alfred Prufrock". It was a two part project, involving a written thesis to appease the English department, and an animated, visual component to please myself (and by doing the film I got to write 30 less pages). It was done in Flash, and was my first attempt at film-making. It actually amassed a surprising number of views on youtube, probably because it concerns one of the most famous poems in the western world, and less because of the animation quality (there's hardly any real animation in the entire thing.)

After graduating I knew I didn't have the kind of skills people would pay me for, so I spent the summer learning Maya and made this film. It's rendered in an odd aspect ratio, I don't know what I was thinking at the time. Also, check out that herky-jerky character motion and demented camera movement. Fun stuff.

But hey, it got me into Sheridan's Digital Character program, so there ya go.  While I was waiting to go to Sheridan I made another film, this time with sound, about monkey-creatures summoning hammers from an alternate dimension and fighting with them. The storyline is unclear, the ending is ambiguous, and the computer's attempt at cell-shading is...eh. The only thing I still like about it is the lightning and smoke effects which I did frame-by-frame in Flash. Another good learning experience.

Then I went to the Sheridan program where I made this film. Mike and his Grizzly Bob accent is the funniest bit:

Survival Tips with Grizzly Bob! from Christopher Scott on Vimeo.

And then after graduating I applied to some jobs, didn't get them, took an iAnimate class, rigged some more things, and am now once again on the job hunt! This is my latest reel:

Chris Scott - Animation Demo Reel August 2014 from Christopher Scott on Vimeo.

So on this blog I'll post animation tidbits that interest me, as well as any new stuff I make. And then maybe one day, once I actually get good enough, someone will read this. And that'll be cool.