Pole Vector Throwing Off The Hand

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  03 March 2007
Pole Vector Throwing Off The Hand

I am doing a typical arm set up with an IK and pole vector constraint to an object. I found that after I put the pole vector constraint on it throws the wrist rotation way off, resulting in the bones being way out of the hand. Would it be best to go in and put the orientation back using the Pole Vector Constraint by changing the offset, or should I go in on the wrist bone and adjust the joint orientation manually? What would be the best fix for the long run?

I have made sure there is no rotation on the joints and that the pole vector object has no history, froze transforms, and centered the pivot.
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  03 March 2007
the pole vectore object is too close to the bones ,so move it away on the z axis (negative)
or you can :
1 move the pole vector object on the y axis to get the initial position of the hand (bones on the skin)
2 disconnecte the pole vector constraint connections.
3 reconnecte ( pole vector)
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Last edited by Mairifsamir : 03 March 2007 at 07:56 PM.
  03 March 2007

Thank you for the response. Actually the first time I did this the pole vector object was about 12 units back, it was there when I took the screen grab because I just applied it again to show the problem.

I will take a look at the other solution you gave that sounds like it could very well fix the problem.

Ill keep ya posted.

Thanks again!
  03 March 2007

Just to update you on the matter I did try the fix you had mentioned and it ended up doing the same thing to me as when I started. I am just going to leave it with rotating the joint orientation to get the bones back to the hand.

I appreciate the help!

  04 April 2007

Make sure you are using a Rotate Plane IK, cause the Pole Vector might not work with the Single Chain IK. Try to set the pole vector object almost completly aligned with the elbow joint, using the front view of you character!
  04 April 2007

Thanks for the reply. I actually did just what you said. I think that because the arm goes from the shoulder to the wrist on the front view thats causing the problem. Its all good now though I just had to rotate the wrist joint back into place.
  04 April 2007
To find the exact position that a shoulder pole vector constraint should go, it needs to be in a plane extended from the positions of the shoulder, wrist and elbow.

The following explains how to find this using constraints, although it would be possible to script it, too, using vector positions.

Create a locator and snap it to the elbow joint. Now aim constrain it to the shoulder and the wrist joint.

Delete the aim constraint, and translate the locator away from the elbow, using 'object' mode in the translation tool. Make sure you are going in the direction which is directly away from the wrist and shoulder (i.e. the opposite of the direction you used for your aim constraint).

By moving it along this axis, away from the elbow, it should be in the required plane to stop any spinning when it is used as a pole vector position.

Hope that works.

  04 April 2007
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