Ik's are changing joint orientation

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  09 September 2008
Ik's are changing joint orientation

I'm having a problem applying IK handles to a joint chain. I figure I'm making a simple mistake but I can't figure out what it is. Whenever I apply an IK handle to a zeroed out joint chain, the joints effected by the IK handle will have slightly altered joint orientation. Does anyone know what is going on? Thanks


Evan
 
  09 September 2008
Did you use set preferred angles, and is was your joint chain slightly bent before IK application?
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  09 September 2008
Thanks for helping out with my question. The set up was a leg with a double knee. The character I'm rigging was modeled with his legs spread slightly so the joint chain is straight but slightly angled to the side. There are preferred angles set into the knee joints. I've noticed that when the knees don't have preferred angles the IK seems to be applied properly but for some reason when I add in the preferred angles the orientation in the joints gets altered by the IK. I still don't understand why though. I hope that helps

Evan
 
  09 September 2008
What you can do is remove the set preferred angles, and if it's possible rotate the knees in the direction you want them to bend just a bit, freeze transform, and re orient the joints.

I've found that set preferred angle only helps when you have a completely straight joint chain, and you want maya to specifically bend the mid joint in a certain direction. If you had a slight bend in your chain, though, maya forces the preferred angle, hence you might get rotation values on your joints upon IK creation. For elbows and knees, i just leave a slight bend in the proper axis so that the ik will bend from there (this is of course with zero rotation values).
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  09 September 2008
That's not a bad idea. I'm working on a cartoon rig and most people say to make the joints straight to give animators a greater degree of flexability when creating key poses. But maybe if I add a slight bend, say 0.001 it would still give me a relatively straight leg but it would take care of the other undeterminable random rotation values. Thanks for the help.
 
  09 September 2008
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