Spine Rig Design
For the purpose of discussing character rigging, we can consider any lengthy chain a spine. This could be the spine of a human, the neck of a giraffe, the tentacle of a giant squid, the trunk of an elephant, the tail of a T-Rex, the spine of a chinese dragon, or even the long serpentine tongue of a certain giant black alien symbiote!
We'll look at a number of different designs and I'll cover how to build them, their uses, and their individual pros and cons.
- The B-Bone Spine
- The Propagating Rotations Spine
- The Bend-O-Matic Spine
- The Bones-on-Curve Spine
- The Linear Curve Tracking Spine
- Making A Spine Twist
Spine Rigs vs Curve Deform
For some characters, it might be more practical to use a Curve Deform Modifier instead of a spine rig. There are advantages and disadvantages to both spines and curves, and you should understand these so you can make an informed decision over which one to use for your characters.
- The first issue with curve deform is that it shares the same Z-axis flipping issue as the Track To constraint. The difference is that it uses the curve's local Z-axis as the up/down direction. Curves have to do this because they have to have a way to determine orientation at any given point on the curve.
- Curves don't provide a way to easily parent objects on the curve and keep them at a constant distance from one end of the curve. This means adding appendages along the curve would be difficult to manage, at best.
- Using a curve will give nicer deformations, especially in sharp corners. The blended weight groups that armatures use compress the mesh around the joint. This is caused by the way that vertex locations are calculated when the influence of one or more bones are blended.
--Wavez 16:56, 28 June 2006 (CEST)