View Full Version : IK with joint rotation limits?

08 August 2008, 10:52 PM
This is cross-posted from the general rigging forum, because I use maya and because this forum seems to have more activity.

I am fairly new to rigging so pardon me if this question sounds a bit obvious.

I am rigging a crab leg, and from my research into the mechanics of it, I have found that it contains 5 single-axis joints.

Now, I could quite simply cheat it and use a standard IK chain on my 5 joints and nobody would ever notice. The problem I am having is that when the leg is raised, it intersects quite noticeably into the body, because (from what I understand) in reality, the joint that permits the major up and down rotation of the leg is offset from the base a little bit. Hopefully the picture can explain it a little better.

Is it possible to setup an IK leg so that I could lock an axis on the base joint at least? Or does this require a much more complex solution?

Thanks :)

08 August 2008, 12:01 AM
Should be able to just lock the two axis you don't want it to rotate on if I'm thinking correctly. You can lock any joints in an IK chain and it should work as one would expect.

08 August 2008, 01:50 AM
To add, just be sure to have two iks for this leg. One SC for the first joint segment, and one RP for the rest. Then you can point constrain the SC to your foot controller and parent both IK to the controller after that.

08 August 2008, 01:59 AM
Thank you guys very much. I experimented with aim constraints as was suggested from the other thread in the General Rigging forum, but I found the behavior to be a little flakey. I've tried a single bone IK to control the root joint, with another IK controlling the last 4 joints of the leg. This seemed to work great!

However, isoparmB, I am going to try your suggestion as it sounds pretty much similar but a lot more elegant than what I found. :D Thanks guys!

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08 August 2008, 01:59 AM
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