2009

1. Bone01
2. Bone02
3. Bone03
4. Bone04
The Start and End Joints are Bone01 and Bone04, respectively. Suppose the
pose shown in the figure is the preferred pose and Bone01 contains a rotation.
If we parent Bone02 directly to the world, the hierarchy from Bone02 will
appear as in the right figure.
When we reassign Start Joint to Bone02, the Zero Plane Map sphere will be
based on the configuration on the right.
■ A: Parent Space is Start Joint. In this case, the sphere that is fixed to the
right configuration is to be parented to Bone01 together. This will be the
same as the one based on Bone01 to Bone04. Therefore, we get the same
normal and chain stays stationary.
■ B: Parent Space is IK Goal. In this case, the sphere stays in the world while
Bone02 is parented to Bone01. When Bone04 is moved to where it is shown
on the left due to the transformation of Bone01, the observer who is fixed
to the sphere that is fixed to the world will see that Bone04 moves away
from the neutral position defined by the preferred pose. The algorithm
then applies the Zero Plane Map to find the normal at the displaced
3406 | Chapter 15 Animation