Simultaneous IKFK Chain

Rigging
, ,
1

Hello-

I am working on a project that has lots of tentacles, and I want to make a system that will make my animators’ lives as easy as possible,

The Goal: create a simultaneous IKFK chain, similar to human IK’s arms, but with more joints and IK controllers. Essentially IK translate drivers with FK rotation overrides.

For example: if the chain has 3 IK controls (1 being the start, 3 being the end), I want IK control 3 to translate IK control 2, and 2 translates 1. However, if I rotate 2, 3 rotates from 2’s axis. Pretty much, I am trying to make an arm with more than 1 elbow.

I have been trying to use matrix math to avoid cycle errors, but I’m struggling to get everything working at the same time without offsets blowing up.

My current theory I’m trying to execute is having a constant offset between each IK controller and its child, and each IK controller rotates from the axis of the parent.

Let me know if you want to collaborate.

Thomas

2

When tasked with similar tentacle problem I just built a basic IKFK rig driving a spline IK rig.

It used the IKFK rig to drive the transform spaces ( nulls/ groups / hierarchy buffers / dummys ) of the spline IK controls. Only the spline IK ctrls drove deformer joints. The spline IK ctrls did not propagate “backwards” to the IKFK system at all. I also had a space switch to “free” the spline IK ctrls from the IKFK system.

Basically the IKFK system was for coarse positioning and the spline IK ctrls were for fine positioning