Challenging (impossible?) IK setup

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  07 July 2008
Challenging (impossible?) IK setup

Hello everyone, I've got a bit of a challenge here...

I'm working on the legs of a mechanical character that has very specific requirements and limitations. It requires an IK setup but at the same time each leg joint must be limited to 1 axis of rotation, and on top of that - a maximum of 180 degrees of rotation in that specific axis. Before starting this problem I didn't realize that Maya's IK solvers don't support joint limits, so it has become quite a task for me. My attempts have been based around collections of constraints and utility nodes that always seem to fall just short of an acceptable solution.

If anyone has any suggestions as far as how to attack this thing I'd greatly appreciate it. I'm sure people have run into this problem in the past - I'd think there might be a simpler way.

Thanks in advance,
  07 July 2008
hi, sounds like a challenge... check out this series and particularly book2...

i dOnt sUffEr fROm inSanIty. I EnJoy eVeRY miNuTe oF iT.
  07 July 2008
Thanks Andrew - Actually that was nearly the first place I looked. Love that series, and when it comes to how I need to limit my joints to only 1 axis - volume 2 of those books has a nearly identical setup. The only thing they don't help with is how to limit the max and min degrees of possible rotation, which is where I'm completely stuck.

  08 August 2008
make another rig with custom attributes

and use it to animate your actual rig- define the limits in the animation rig.

the ability to do this is handy in all sorts of places in maya where you might want to idiot proof a production scene..
  08 August 2008
What i've done in the past to limit rotation of an IK setup, would be to have a series of joints setup with IK, then have another set of joints that the geometry is bound too. Take the rotations from the IK setup and feed just the axis you want to the bound setup. to limit put a clamp node between the ik rotations output and the bound inputs. This worked for an auto-clav setup i built.

hope that helps, if you want to upload your scene (.ma please) i can try to set something up so you can see what i mean.
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  08 August 2008
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