Setting up an IK chain with multiple bones and a constraint

gloggen

Hi,

Is it possible to create an IK constrained chain with more than 2 bones (excluding the restraint bone itself)?

When I select more than two bones and try to create a new Constraint, I get the following message:
"Select one or two bones to create an IK constraint".

Is there some other way of creating a chain like this, or will I have to divide the chain up into multiple 2-bone segments and hand-animate it?

The same chain works great when using the "Pose" tool, but I want something more permanent =)

Thanks,
Joel

Søren

Unfortunately not. 2 Bone IK is the max you can get. The short reason for this is because you will be able to manipulate IK at runtime and it's fast with 2 bones. I'm sure there are technical reasons for this as well, but I can't comment on that, maybe Nate will be able to shed a little more light on it.

Mitch

On the Unity3D front, there are plenty of solid 3rd party IK solutions for arbitrary chains. Using my soon-to-be unity extensions you can make use of those all you like at runtime.

gloggen

Cool, thanks for the update!

hydrip

Will this be fixed in a future update? Why Spine can't do this while other animation tools can?
Right now it's next to impossible to create fluid chain animations because IK can only handle 2 bones.

Søren

I can't say if the bone count will be increased in the future, but keep in mind that you can use the pose tool which allows you to use as many bones in your IK chain as you want. At runtime IK is heavier than FK and it also complicates the runtime a great deal. For many games IK will actually be plotted to FK due to the extra overhead. Personally I wouldn't even use IK for a chain animation, FK gives more control and using additive rotation gives a pretty smooth look. Maybe you can show an example of why you would want to use IK for it ?

hydrip

An example would be a robot with legs that have bendy "chain" legs made of tens of joins/bones.
Loading Image

Søren

It's a good example and it would be hard to do with pure FK. Multiple 2 bone IK chains could be used for it, I think 4-6 bones should be fine for that unless you want it to do some really crazy movement. The skinning just needs to be very smooth. For the vine example video I put up it looks like there are far more bones in there due to smoothing the skinning a lot. You can see it here http://youtu.be/RpVMiUC8Ewk?list=UU_ijs ... M1P30f8Gaw