CGTalk - IKRP confusion

faultymoose

09-06-2006, 06:25 AM

I have come across a problem that is totally confusing me, but which has the appearance of an easy solution. I'm not really able to post screenshots from here, but I will when I get home if required. I'll try to explain as simply as possible:

I have a simple, three joint IK 'leg'. This is all that is in the scene.

I add an IK handle between the 'hip' and the 'ankle' joint. Works like a dream.

I add a pole vector constraint, and it works as intended up to a point - but when the 'ankle' is raised above the knee's original position, the knee begins to deviate from aiming at the pole vector, until it seems that the pole vector is no longer having any affect at all.

I hope someone else has come across this problem and can help me out.

Cheers

isoparmB

09-06-2006, 07:28 AM

Did your leg setup not respond to your pole vector, or did it flip when it hit a point? Just want to clarify. Usually RP ik's flip when they go beyond the rotate plane for the pole vector, hence their name. The trick is to animate the pv so that the leg never hits the rotate plane, though I don't know if this is your problem.

faultymoose

09-06-2006, 07:36 AM

When the ankle was raised above the knee's original position, there was no immediate or sudden flipping, but the knee began to bend off to the side instead of pointing at the PV. The higher the ankle is raised, the more dramatic this becomes, until the leg stops bending altogether at a knee-angle of about 15 degrees, and starts flopping all over the place.

The PV locator remains a few feet 'in front' of the leg at all times.

I'm really sorry I can't describe this any better, I'll post images tonight.

isoparmB

09-06-2006, 08:18 AM

That's to be expected. Try moving the pole vector up as well and se if that fixes it. Generally the pole vector works best when in front of the joint chain where it bends, as pole vector constraints do not change the lengths of your joints.

On a final leg setup, I usually parent the pole vector to the leg controller. This leg controller usally has the leg IKparented to it as well. Although there will still be times when you'll need to animate the PV.

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