Monday, November 10, 2008
Stretch SplineIK for head rig Part 1
The joints chains for head
As the cartoony style of the animation, the head of the character may not be maintained in the anatomical structure. The range of the movement is not only based on the lower jaw and the neck. According to the animatic, the upper jaw of character is not stick rigidly on the head joint and lifts up from the lower jaw, the eyes and forehead has to been stretch independently. The rig of the head has to basically broken in order to achieve the requirements.
The head motion of character in the animatic
So, I broke the head rig into four sections, each can be moved and stretched independently to the others and has to been linked one by one:
1. Forehead, eyes and nose.
2. Upper jaw
3. Lower jaw
4. And neck
The head had been into 4 parts for the rigging
The rig is used in each part which has to allow for bend, stretch, twist and independent motion of both ends. There are a few different techniques to achieve those effects. The most typical way is the stretchy splineIK system which had been presented by Jason Schleifer of Dreamworks & WETA in the DVD “Intergrading A Creature Animation Rig Within A Production Pipeline”. The content of the DVD is actually AWGUA Maya Master Class August 2001, although the technique has been existing for almost 8 years already, it is still popular and using for spine setup as it is easy to setup. The ribbon spine is another new way of building an IK-like spine rig which presented by Aaron Holly, lead character technical director of Digital Domain, in his DVD “Rigging For Feature Animation”. This technique gives animators greater control and more flexibility over their spine animation, yet this technique has to be involved with Maya Hair follicles, follicles is only featured Maya Unlimited version and may be accessed by some users. The stretchy splineIK system is normally used for the spine rig, yet I intended to use the technique for the head rig in my project.