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View Full Version : IK Leg setup causes unwanted rotation

Udapud
12-08-2008, 01:45 PM
Hi there chaps/chapesses

I'm having a huge problem with my IK setup. I have a simple rigged and skinned character.

SEE ATTACHMENTS FOR PICTURE...Everytime i try to move the leg backwards or forwards, it will reach a certain distance and the IK will rotate the foot.

The setup i am using for each leg is Hip joint>Knee Joint>Ankle Joint>Toe Joint. The Iks go from Toe to Ankle and then Ankle to Hip. movement in the skeleton works fine and the heirarchy seems ok, and i've used this setup before with no problems. But i have had this problem before with a seperate rig.

I have read things about using a pole vector constraint but im not sure how to use it and when ive tried it messes up the leg compeltely, throwing out all rotation and making it look like its been microwaved!

Why is the Ankle to Toe IK rotating the Toe joint after the Leg controls move a certain distance forwards or backwards?

Cheers in advance.
Mike
mberglund
12-08-2008, 02:05 PM
check your joint's Local Rotation Axis, make sure they are correct.

if the joints are straight, try setting a preferred angle on the knee joint.

create a locator place in front of the knee. Select the locator and then the ikhandle. create a poleVector constraint. if you get weird rotations and results then the way you created the skeleton is messed up.
Udapud
12-08-2008, 03:10 PM
Thank you very much for that. I've been trying to figure out a way to sort this problem out for years! and whatsmore I understand how it works which is the main thing. So thanks for that.

I actually applied two locators for both IK's (from hip to ankle and ankle to toe) so simply moving the locator cancels out the twist completely.
Udapud
12-09-2008, 04:49 PM
OK new problem

It seems that the main leg control rotation wont work properly because of the pole vector constraints...

So when i try and rotated the leg (from the Hip>Ankle IK group) it no longer rotates as it used to, it does rotate but only at the bottom of the leg and that aint really useful...

any ideas?
mberglund
12-09-2008, 04:52 PM
I wrote a tutorial on no-flip knees and poleVectors maybe this will help answer your questions.
http://faithofthefallen.wordpress.com/no-flip-knee-setup/
Udapud
12-11-2008, 01:51 PM
Just for anyone else who expereinces this issue, the pole vectors control the direction of the knee! *slaps forehead* doh!

I didnt do your tutorial Mberglund but i did read it which is what filled in that little blank.

Cheers
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12-11-2008, 01:51 PM
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