View Full Version : How to set keys on Ik/fk switchable arm?

11 November 2007, 11:48 AM
I rigged a character with a Ik/Fk switchable arm. I used an ik arm , a fk arm, and a bind arm which is pointConstrainted by the first two arms . The seamless switch was achieved ,BUT when setting keys problem arose. It seems not that easy to set keys properly . Any one can help me out? and what methods are used for this particular potion(ik/fk switch) in real productions?
Thank you !

11 November 2007, 09:44 PM
you don't need 3 chains. you just need one.

if you key the rotations of the joints and FK is on then it follows the FK keys, otherwise in IK mode it will ignore those keyed rotations and with this you can blend.

try it with one chain. you'll be surprised.

11 November 2007, 02:03 AM
thank you very much Geordie! That works perfect! Not to hard to setup ,and the result is awesome. You are really a kind man.Thank you!

11 November 2007, 04:11 PM
Hi Geordie.

I have no idea in stretching with single chain IK /FK switch, I don;t know how to matching the scale after switch, or should I use only translate for it? any suggestion on it?



11 November 2007, 05:57 PM
I just found out about this like the other day about the fk ik blending. I've always only known of the "three joint chain technique". And this isn't really anything new since this exists in maya 7.0 which I'm using. So what's the idea of using the 3 joint chains when It's already implemented in maya?

11 November 2007, 09:45 AM
I think the 3 joint chain system comes from ppl using curve controls to shift the ik handles about so it looks nice n user friendly. I used to faff on with this but now just animate the ik handle directly... theres a nice little IK blend slider there and the twist option all under one node. Ok the IKhandle might not look as pretty as a curve control or something but it does the same job if not better :)

-After creating it, I freeze the IK handle so its transform is 0,0,0
-I then create a pole vector constraint though this isn't really necessary as the pole vector is controllable with the ik. This is just personal preference for me.
-I then check to make sure the pole vector hasn't adjusted my arm rotation in any way - usually it has, so I'm always careful to make sure I do this step PRIOR to any rigging. That way the bind pose isn't shifted.
-I then do my skin binding.

not sure if that makes sense and there are prob a few ppl who will disagree but to me its important that any rigging & control setup DOESN'T MOVE. That way if you zero out all controls on the character you end up in the EXACT bind pose

11 November 2007, 12:22 AM
Thank you for the explanation!

11 November 2007, 02:23 AM
I think the 3 joint chain system comes from ppl using curve controls to shift the ik handles about so it looks nice n user friendly.
Before version 5, Maya did not have a built in IK/FK option. While the default IK/FK switcher will work for most rigs it can still be broken under certain conditions. Besides the ideas behind the 3 joint chain system are still useful to know :)

11 November 2007, 03:05 AM
just struck me. I'm not sure if it'll work but for you who are using the single joint chain and want some iconic represenatation, try typing this command in script editor:

parent -add -shape right_arm_ctrlShape right_arm_ikHandle;

11 November 2007, 03:17 AM
Alternatively you may select the 'controller' geometry, then the target object and use the following command: parent -r -s;

11 November 2007, 03:56 AM
thanks! that's even better!
Is there a way to undo this parenting with another command perhaps?

11 November 2007, 06:12 AM
I haven't find a better way to undo that, just delete the curv shape.:shrug:

11 November 2007, 10:13 AM
but when deleting the curveShape, isn't this goin to delete the joint or ikHandle itself?
What happens exactly, when assigning this curve to a joint or ikHandle.

11 November 2007, 02:06 PM
if you select the curv shape node in outerline or hypergraph properly ,it won't. if just select in cam view , you grab the curve it seems to go one step up selecting the joint/ikHandle.

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