2009

You can move and animate the spline vertices to change the curvature of the
spline. Usually, a helper is placed at each vertex to assist in animating the
spline. The spline curvature is then passed on to the entire linked structure.
The bones themselves do not change shape.
Normally the number of spline vertices and bones are the same, but you can
use fewer vertices for easier posing and animating a long multiple-bone
structure with just a few nodes, as opposed to animating each bone
individually.
Spline IK provides a more flexible animation system than other IK solvers.
You can position vertices/helpers anywhere in 3D space, so the linked structure
can assume any shape you want to give it.
A helper object is automatically placed at each vertex when Spline IK is
assigned. Each vertex is linked to its corresponding helper, so a vertex can be
moved by moving the helper.
Unlike the HI Solver, the Spline IK system does not use a goal. The positions
of helpers/vertices in 3D space is the only factor that determines the shape of
the linked structure.
3446 | Chapter 15 Animation