View Full Version : FKIK Switching Problems

03 March 2007, 01:54 AM
I'm trying to setup an FKIK switch using blendTwoAttr utility nodes, and three joint chain arm. That said I'm having a problem with the FKIK switch. I've wired up all the proper connections and nodes, and the switch works as expected.

However, every time I setup an IK handle on the arm, I get slight rotations all down the IK arm, on all the joints. It seems to happen regardless of the IK setting, and regardless of whether the Ik is setup before or after the switch is created.

Every time, I switch to IK mode the driven arm moves to the IK's position but is slightly misaligned. It follows the Fk arm just fine however. I'm still using Maya 7.0 so I'm no scertain if its a bug with the IK. Any help would be greatly appreciated. Thanks!

03 March 2007, 04:10 PM
More than likely the IK arm is not planar. Meaning that the arm is not in a straight line in one axis. You have to have the arm straight in 2 axis. The elbow can be bent in the direction of the actual bend but not in any other axis. If you take a look at the joint orients for the elbow, you should have only one axis with values. The other 2 should be zeroed out. A rotate planar IK has to be PLANAR in order for the iK to solve correctly. It took me sometime to figure this out as well. You should also notice that when you switch to FK that there are values in all three channels in the elbow. This is also a clue that the arm is not planar. In FK there should only be a value in one axis. Your elbow can only bend on one direction. So, if you've set it up so that Z is the rotate for the elbow, X and Y should have no values when you make the switch from IK to FK.

Also, if the polevector is not built correctly and placed in the correct spot, you will get a pop when you make the switch. Look into one of the zoo scripts that Hamish McKenzie wrote. He has in his rigging scripts a proc for placing a polevector in the mathamatically correct position.

Hope that helps!!

03 March 2007, 04:18 AM
Thanks, for the reply I'll look into the script.

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03 March 2007, 04:18 AM
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