Animate Ik to Fk switch

fns

Hi everyone!
I was hoping if anybody could help me with animating a smooth switch from ik to fk.
The character that i am animating si making a jump.So while his feet are sticked to the ground (reverse foot rig) he is doing a jump, so as he is moving up in the air i keyed the "Pelvis" and "Feet" controls, and also the ik/fk "Mix" slider of the feet constraints.
The problem is i dont know how to make this transition seamless, without the bones to snap in the keyed moment where they switch to fk.

To understand this more clearly here is a link with the problem situation

https://www.dropbox.com/s/atkxpo0fq38oj0l/ik-fk-switch%20snapping%20bone.mp4?dl=0

Thank you so much in advance!

Nate

How are you keying the mix? You can key the mix to adjust between 0 to 100% and 100 to 0% over time. This will give you a smooth transition to/from FK/IK.

fns

Hi Nate and thank you so much for your answer!I pretty much did that, but i was curious if there was any solution to do a completely switch from 100 to 0, so then i could have complete control on the of motion.But i guess what you say is the best option to have smooth transitions.

Nate

If adjusting the mix over time, it's not necessary to be super exact, but if you want to, it is possible. You can use a stepped curve on your keys to instantly transition between 0/100%. When doing that, to avoid snapping:

Going from IK to FK, you'll need the FK bones in the exact same position as the IK bones. One way to do this is to select the IK bones, ctrl+C to copy the transforms, then click the visibility dot next to the IK constraint in the tree. This allows you to modify the FK pose (which can also be done by setting the mix to 0%, but pasting a bone transform doesn't seem to apply unless the constraint is hidden

we'll look into that). Select the IK bones, ctrl+V to paste the transforms. Now you can show the IK constraint and when you adjust the mix, the bones won't move.

Going from FK to IK, you need to place the IK target at the exact tip of the child IK bone. One way to do this is to create a bone parented to the child IK bone, then set its local translation to x,0 where x is the length of the child IK bone. Now that the bone is at the exact tip of the child IK bone, select it, ctrl+C to copy the transform, then you can delete the bone. Next select the IK target bone, ensure World axes are selected, then ctrl+V to paste the transform, placing it at the exact tip of the child IK bone. This is a bit of faffing around to get the IK target in the right place, it would be nice if there was an easier way.

fns

Nate, thank you so much for your answer!This is just what i was talking about.I will try to put this in practice and as soon as possible will come back with an answer about how it worked.

So ive tested the ik to fk and its all working good.Thank you again for everything!

kaix

Hi!
I would like to call back this thread since the switch IK FK solution doesn't seem to work on the actual version of Spine. Is there any new solution to copy bones transform from IK to FK easily?

Nate

Hmm what was I saying 2.5 years ago? 😃

Note Spine no longer ha a visibility dot next to the IK constraint in the tree to temporarily disable the constraint. Instead you can set the mix to 0 to have the constraint no longer applied.

I tried ctrl+C on bones that have an IK constraint applied, set the IK mix to 0, then ctrl+V the bones. You're right, it doesn't work any more because it copies the FK pose. We'll fix this in 4.0.50.

Even then you still need to be careful, you should have the local axes selected when you paste. If you have world axes selected, it won't give you what you want.
Tools - Spine User Guide: Axes

If that doesn't help, please describe what you are trying to do and what you tried.

kaix

If it's a bug, then this was the answer I need. Thanks !