My goal is to make an arm rig which can easily switch between FK and IK without using scripts (I’d be willing to use pre-made and tested scripts if there is a consensus that it’s the best way to go.)
My first attempt at this has produced cyclic dependencies. Here’s how I’m trying to do it. I have two identical bone chains, one for FK and one for IK, a FK / IK switch slider, and an IK target (let’s call it _target). The FK chain bones copy rotation from the IK bones only if my IK slider is in IK mode. This seems pretty conventional.
Now the part I’m having problems with. I want _target to stay with the end of the FK chain in FK mode. This way when I want to switch back to IK mode I can just key _target where it is, and move the slider. To do this, I add a copy location constraint to _target so that it copies the location of my FK chain. This is all well and good, because it only has influence in FK mode (because in IK mode this would be a cyclic dependency.)
The problem is that blender complains about a cyclic dependency even though the copy location constraint has 0 influence. Is this expected behavior? Is there a way for an IPO driver or such to completely enable/disable a constraint to prevent cyclic dependecies?
So there’s the problem, and I realize this might not be the best way to approach the solution at all, so other suggestions are very welcome.