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View Full Version : Need help with a 3-joint IK leg setup


chazriker
06-01-2010, 06:24 AM
I've done searches on this topic and while many others have posted similar inquiries, I can't seem to draw any kind of conclusion from what is posted. I'm familiar with setting up IK for human models but now I'm stuck.

I have this very simplistic placeholder model here I'd like to animate. Each segment is a bone, and each part is 100% weighted.

http://www.ac.tanadrinestudios.com/Forumpicholder/d2.jpg

I went ahead and posed this thing using FK to get a better idea of how I want this thing to stand... again this is a placeholder and I intend to re-make this model in detail:

http://www.ac.tanadrinestudios.com/Forumpicholder/d1.jpg


Ideally, I'd use 1 controller for each leg and use FK for fine adjustments, but the problem I have is that IK only ever seems to work properly on a 2-bone setup. The problem is, of course, that one of either 2 things happens when I set up IK:

a) The leg works... but is very shaky and sometimes unpredictable and out of control

b) The leg is as rigid as a steel plank

How do I get it to work with 3 bones? Is there something I'm missing? Is using pitch as my IK setting not enough?

http://www.ac.tanadrinestudios.com/Forumpicholder/d5.jpg

To give you an example of how I typically setup my models, I'll provide a human rig I made. I have extra joints in place to prevent "IK pop". Basically I only set up the bones to work with pitch and I can control the legs pretty nicely, the extra bones at the top of the legs allow me to twist the legs with FK as needed.

http://www.ac.tanadrinestudios.com/Forumpicholder/d7.jpg

So... does anyone have any suggestions on how I can approach the 3-joint spider leg setup using only ONE goal? Anything that could get me pointed in the right direction would be greatly appreciated!

Dodgy
06-01-2010, 06:30 AM
Make sure you have a little bend in it when IK is off. This tells the IK which way the leg should bend.

kojean
06-01-2010, 08:41 AM
These videos may be helpful. h2oStudios explains how to rig an insect (using PLG_IK (http://homepage2.nifty.com/nif-hp/index2_english.htm)):

http://vimeo.com/11476451

Originally posted in this thread:

Need help In learning how to rig (http://www.newtek.com/forums/showthread.php?t=105436)

chazriker
06-01-2010, 09:07 AM
Your responses have saved me a ton of frustration. Thanks!

abdelkarim
07-08-2010, 10:29 AM
Your responses have saved me a ton of frustration. Thanks!

this is what im talking about. and Pelvis For move all Body ????