View Full Version : Multiple IK

03-11-2005, 10:12 AM
Hope I make sense. I've done my homework but am still stuck.

Setup IK for my arm from shoulder bone to wrist bone. Then setup IK for my finger, from Index 1 to Index 4. When I move my null for the arm IK my null for the finger wants to stay at its world coordinates since it is not parented to anything, therefore distorting my finger. I understand WHY this is happening, but I do not know how to fix it.

I went through Tim Albee's book but he does not get into rigging the Hand. The Zombie video tutorial does not either. I am quite sure it is something simple but still seems to allude me.

super advanced thanks for any help.

03-11-2005, 10:48 AM
Most people wouldn't use IK for the finger, but if you still want to, you could parent the finger goal to the hand goal, so as the hand moves, the finger goal will too...

03-12-2005, 09:15 AM
I thought about that one, but when I do that the finger IK wiggs out a little every time I move the arm IK goal. See attached. First image is without trasformation, the other two show just a little movement of the arm goal. Maybe this is why people dont use IK for the hands? Would it just be easier to use key frames? What is the best method for the hands?


Thanks again.

03-12-2005, 09:33 AM
Hmm It shouldn't really wig out like that.. Would it be possible to see your scene?

03-12-2005, 10:56 AM
You can't have two IK's going on in the same limb. Lightwave way of handling IK is fairly braindead. It doesn't know where things are after an IK event. Expressions, IK and Targeting don't "see" the results of an IK solve (Motion Option Expressions do because they can be calculated after IK), and a second IK would not either. Other software lets you create a stack of commands where you can specify which command happens at which time.. Then expressions or IK can be used on bones effected by IK.

Maybe some day Lightwave will get this feature. It really needs it.

03-12-2005, 11:21 AM
You can use multigoal IK chains but its not pretty.
Ive never used IK EVER for fingers. Doesnt mean that there might not be a time where you might use it that way but for me it would be rare. About the only time I would is if the fingers have to stick to something for some reason. FK is what I use 99.9% of the time.
IF I were to do something like that I would just use IKBooster. You have IK and FK available at the same time. You could animate the fingers using FK or IK by grabbing the tip of the finger or any other controller. Since each joint is a controller that means you could animate the finger from any joint. You would just need to define where the IK starts and stops. :)

03-12-2005, 03:50 PM
Okay, it does wig out in my test scene..... But I have a solution. Parent the finger goal to the hand BONE.... Then you can use 'Match Goal Orientation' or whatever to control it (the hand), and it works fine.

Could have sworn it was fine, but maybe I'd just never tried it with MGO on before in a multi Ik system. It works (but not in the way of MGO, more like a spline Ik system)

03-12-2005, 04:50 PM
I thank you all very much. It was all very helpful. Once I get this arm/hand setup I will post my results in the WIP section.

03-14-2005, 09:20 AM
wow, that IKBoost is super cool. Slick as snot.