why do Ik/fk switches exist

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Old 05 May 2013   #1
why do Ik/fk switches exist

Hi,
newbie to rigging here with a question
I've been wondering why do ik/fk switches even exist in rigs? Couldn't there just be ik and two rotate controllers that are operated like fk but actually control the ik controllers, like for an arm, the hand controller and the pole vector controller?
Odd
 
Old 05 May 2013   #2
Ok after a bit of digging in I found this must be because of cycles.

Now it would be nice of course nice to have the ik controllers parented under the fk controllers like described (fk mode) but then automatically switch to ik mode once an ik controller is moved (ik mode)
fk controllers could be parented under the joints then as long they're not active so once they are used again they're in the right position already. I guess this is becoming to software specific for here.
 
Old 05 May 2013   #3
Hello,

I think a lot of it has to do with what animators want, they want a system which is easy to work with and gives quick viewport feedback.

The advantage of using the traditional system is that it's very simple to work with and gives realtime feedback. If you had a IK and FK in one chain then potentially the complexity could cause the feedback to not be realtime.

That being said, Biped and CAT in 3ds Max both use the system you descirbe.

I asked a very similar question on The Area, you see the responses here:
http://area.autodesk.com/forum/auto...---best-option/

Hope this helps,
-Harry
 
Old 05 May 2013   #4
Originally Posted by oddforce: Ok after a bit of digging in I found this must be because of cycles.

Now it would be nice of course nice to have the ik controllers parented under the fk controllers like described (fk mode) but then automatically switch to ik mode once an ik controller is moved (ik mode)
fk controllers could be parented under the joints then as long they're not active so once they are used again they're in the right position already. I guess this is becoming to software specific for here.


Actually, this approach is what I've stated leaning more towards for ym Ik to FK blending setups. It definitely causes cycle errors when using more complex setups like forearm and auto clavicle stuff. However there are work arounds.

It took me awhile but I finally got my FK controller parented IK system to work with an auto clavicle though it did take some work arounds to fix the dependency loop.

To me personally. The FK parented Ik controller approach really shines for 3 main reasons:

1.) It allows you to set up a really complex IK system and then almost as an after thought jsut slap on some FK controller and parent constraint the IK controls to the elbow control and a empty world position group node. The setup time is cut in half for any limb control.

2.) It gives you the ability to have the Ik controls follow the arm for jumps and twists and you can use the FK controls to get your arcs while still in Ik mode. Make you initial arm swing, then without any switch just start moving your Ik control.

3.) The blending is just as smooth and clean as the 3 bone chain color blend method, and you are using less chains. In fact it's possible to set this up with only one bone chain and still get all the functionality out of a 3 bone chain rig.

The only real cons I have found are that more complex setups do give dependency loops, and the FK movement get's off pivot if you rotate in an axis it's not meant to go like for arm breaks.


https://www.youtube.com/watch?v=CEnx-qPhWRY
 
Old 05 May 2013   #5
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