Warning: This is an experimental feature. Stability is not guaranteed.
Using Spline IK allows you to create curves for controlling joint chains.
Long chains of joints are often used for things like tails. Such chains can be cumbersome to animate, as they include lots of controllers and rigid bodies. There is, however, a way to make things simpler:
1. During rigging, create a few (two or three) Rigid Bodies for the entire chain.
See Rigging Complex Skeletons to learn how this can be done.
2. Second, you’ll need to finalize the rig.
Spline IK does not work with prototype objects.
3. After the rig is complete, select the Point Controllers associated with the joint chain.
You only need the Main and Direction points; Additional points should be ignored.
4. Switch to the Joint Mode and add every joint in the chain to selection.
5. Open the Objects menu and select Rig additional → Create Spline IK:
This will create a curve that will control the joint chain.
You can bend this curve by moving the Point Controllers on its ends:
Applying Spline IK to joint chains produces much more smooth, natural-looking deformations.
The curve itself, however, cannot be visualized in the Viewport window at the moment.