View Full Version : Bad Arm rotation Ik with Cat

02 February 2011, 11:29 AM
Hi all !

I've got a simple but very annoying problem. I try to rig an arm (on a robot) with CAT but my shoulder is lower than my elbow. So when i create an Ik the rotation on the elbow is bad...

The basic horizontal rotation should be straight but i can't do it like this because the shoulder rotation must be in the center.

like this

02 February 2011, 01:01 PM
Make sure the model (geometry) has a better T stance, the IK of the arms are calculated from the setup pose, if that's not straight the IK will not work for you. Another option is to try to add and IK handle (modifier panel add upnode), but I think it will not work out in the end. Remodel is the best advice and be sure to test this hypothetical solution first!


02 February 2011, 07:21 PM
Hello !

My mesh is in perfect T position. But I found a solution yesterday.
Because the character is a robot he doesn't have a right shoulder pivot. So the arm rotation is always bad between the arm and the forearm as I explained in my first post. To correct this i simply make my bones arm horizontal (as it should be) and create a tiny cat bone in the shoulder's center and linked it to the first arm bone.
So the ik act right (for the elbow rotation) and I link the shoulder mesh to the tiny bone so the rotations are correct too for mesh.

As you see in this picture.

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02 February 2011, 07:21 PM
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