View Full Version : ik/fk match question

02 February 2008, 10:44 PM
So I am working my way through the IK/FK match idea and I get IK to FK pretty easily, the bottom line is put the IK bones where the FK are.

for FK to IK though, how do you figure out where to tell the pole vector to be?


03 March 2008, 02:55 AM
Hi Stankluv,

Im looking into the very same problem at the moment and came across this thread at the 11second club.

The last post has a link to a script which does exactly what you want.

On another note, but similar to the question, why would you not just use the following set up for a single chain IK/FK setup.

1. Create Shoulder, Elbow and Wrist Joints
2. Create a RP Solver from Shoulder to Wrist with default properties.
3. Move the IK handle for IK, then rotate the shoulder or elbow joints for FK.

No switching or fussing needed....apparently.

Im not suggesting this is revolutionary or anything, just wondering if anyone has gone down this route and hit a wall. What I'm trying to achieve is a single chain IK / FK setup similar to spine rigs where both FK and IK control is possible without the need for a switch. Anyone care to pitch in with ideas on why not to use such a system?

Sorry if this is a thread hijack, but hope the link helps.


03 March 2008, 09:21 AM
OK! I have just found a reason my system wouldnt work. As soon as you key the IK Handle you lose the ability to move the joints in FK.....Ha! :shrug:

Back to the three joint chain....for now!

03 March 2008, 07:30 AM
This may be of help.
I created this video to help explain one way of setting up an IK/fK arm with switching/matching.

There is a link to a sample file and comes with the code for setting up the fk/ik matching.
***Note that the sample file requries some zoo scripts installed so you'll need to watch the video to know how to install.

The setup is pretty straight foward and easy to follow.
**Video file size is large and may be slow loading. You can download the flash video if you wish manually by taking the link to the video and subing ".html" with ".swf".


03 March 2008, 03:41 AM
instead of running the script is there a way to set up n enum attribute and applying the xform process in the hyper shade?

Thanks for posting that as is, I just get nodes better.

03 March 2008, 09:11 AM
I'm not quite sure what you mean by having an enum attribute apply a process in the hypershade. To get an ik to fk or fk to ik there will HAVE to be some sort of script/expression of some sort. There is no node in maya that will automate this for you. What's wrong with a script? They don't bite...unless you program them to do so :).

03 March 2008, 09:27 AM
scripting is ok, I am warming up....I am a bad mutha' with the ^c and ^v...

but I can make nodes sing : )

I am thinking and am seeing a possibility that I will try and get on tomorrow that might work but throw out any blend possibility...we'll see.

03 March 2008, 09:21 PM
To go back to the first posted question. I would just create a locator that is parented to the fk_shoulder joint and when you need to switch, snap the poleVector_locator to the fk_locator for the correct positioning. So you would have two locators: 1) That controls the ik poleVector and a fake one that just follows the fk shoulder around.

Maybe this helps... I think sNolan did something like this in his video.

03 March 2008, 11:55 PM
Hi folks, i have been with the same question in my head for a while... and i joust found a video that makes exactly this thing, is a example rig that no jump from ik to fk changing the positions, what it does is keep the position in fk or ik. I think that has to do with the thre joints chain tha someone says before. The link is:

I dont know hoe to do that, i joust know the clasic way whit the switcher that makes to diferent positions for ik an another for fk, you know what i mean... does anybody know a tutorial that explain this system?... :shrug:

03 March 2008, 12:29 AM
Gonzalo, this setup is similar to what I explain in my video tutorial with a few different things. Mine does not incorporate the stretch part of what the youtube video shows and mine uses a RMB menu instead of a marking menu. Marking menu is fine too but there is still a script that is all doing this under the hood for both of our setups. My preference is the RMB click so I don't have to make a hotkey. Just my $0.02...

And yes, what mberglund had mentioned about the locator parented under the Fk shoulder, I explain this in my video.


03 March 2008, 07:54 AM
mber, the answer to the original question is when snapping from FK to IK place the pole vector twice as far (arbitrary, but apparently "far enough") down the elbow joint's -x LRA as the bone to the wrist is long.

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