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May 11, 2007

lsgl: rigging tentacles

by sven at 11:59 pm

Today's goal was to animate an Elder walking. Didn't happen.

Before the Elder can walk, it needs "rigging" -- that's the CG equivalent of a puppet's armature. So, I wound up spending the day experimenting with different rigging strategies.

"Welcome to Hot Dog on a Stick!"

There are 560 bones in an Elder. And each one of them needs several settings adjusted in order to function correctly. Gack!!

How I'm attempting to manage the problem: Each one-fifth of the Elder is a separate piece. If I can rig just one face (112 bones), then I can glue five copies together to make the complete critter.

[I'm also adding an object inside the Elder, which I'm nick-naming the "diaper", to help hide seams.]

I thought maybe I'd color-code the different sides of the Elder, so I can more easily keep track of which face I'm working on. At the very end of animating, I can switch the skin back to black.

single-bend legs

I'm hoping that I can use Inverse Kinematics (IK) on the legs. With IK, you can give a chain of bones a "goal". When you move the goal, the bones will follow it as if they're a rubbery spine... Basically they can move from being a straight line to being bowed, and back again.

Obviously the shape of a single bow (like the letter "D") doesn't simulate a tentacle very well. I'll add in more. I just wanted to start simple -- IK's kinda tricky at first.

multi-jointed leg

Here I'm just working with one-fifth of the Elder. There are three IK chains -- three letter D's. The concept looks fairly sound... But I need to work more on the placement of the "joints" between chains.

wrestling with joint position

I made another attempt at rigging with four chains in the leg -- approximating hip, knee, ankle, and toe. Unfornately, this version got all weird and kinky on me. I think the issue is that I need to make the four IK chains have different strengths.

* * * * *

...Perhaps you've noticed that this model is different from the one that I was working with yesterday. Seeing the Elder as line-art, I suddenly realized that I've been using the wrong model for the past few weeks!


The important difference is that the model I've been working with today has two fingers. Gotta have fingers if it's going to hold onto anything in this story. Chances are I won't go back and change the shots I've done. It's doable -- but the Elders are so cloaked in shadow, I'm hoping it's not necessary. We'll see.

posted by sven | May 11, 2007 11:59 PM | categories: let sleeping gods lie