View Full Version : IK in arm goes crazy

01 January 2004, 05:00 PM
hey guyz, thanks for your help in the past!

so i have an arm with IK and it goes crazy when i try to move it. it didn't do this without the hand, but the moment i added the hand it went insane! the arm is parented, no binding since it's a robot.

have i built the hand wrong? is the hand the problem? maybe it's the way the bones are oriented?


Matt Leishman
01 January 2004, 07:41 PM
I'm having a hard time deciphering what exactly may have happened given the details you've mentioned about how the ik was set up.

Please give a thorough step by step of what you did to set up the arm joints and the creation of the ik in relation to them, and I'll do my best to try and point you in the right direction.


01 January 2004, 10:53 PM
i figured out that my locator is messing it up. but there's too many attributes i added to it, ie-finger curls and stuff.

i parented the whole arm, that means the shoulder is parented to the shoulder joint and so on.

what do you think? i don't know if there's a solution except doing it all over again.

btw, how do i add a photo here? instead of it bein a link?

02 February 2004, 03:59 AM
This is something i was writing for somebody else.. but it might serv you as well.

*I think you have a problem with the way your creating your Arms and IKs.

What i recomend you do:

First you should delete the old IK, then you should rotate your arm as the way its supposed to rotate by default, then right click on that joint and use "set prefferd angle", then rotate your arm back to its original position. (doing this your telling the arm that thats the way it should rotate... it doesnt matter how much you rotate it, it simply takes the rotation axis.)

then create your IKs with the option RP.
Now create two locators.. one for the wrist and one in the elbow... move the one on the elbow back by a nice distance.

Then select the new locator on the wrist then shift select the IK of the arm and use (constrain/point), now when you move your wrist locator your arm should move.

Now, to avoid loosing your set driven keys and atributes you can select the old locator then the new locator and (constrain/point) now your old locator moves the new locator that has the new IK setup and you didnt loose your atributes.

Then select your elbow locator then shift select your IK again and use (constrain/pole vector)

Now when you move up or down your elbow IK your arm should rotate.*

Hopefully all goes well and your arms move nice again.

BTW... parent your hand to the arm joint.. never to the IK

You can also create a new locator and parent it to your arm joint, then make a point constrain from the hand to the locator.

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