Three Bone IK

Hi. I was wondering if anyone has a good way of doing three bone IK? I am rigging up a leg for IK, I have the foot planting just fine but where I am blending out the IK as heel comes off the ground but the foot slides underground because the animation still has the toes on the ground. I figure a three bone chain would allow me to keep the toes planted.

Thanks
Russ

The problem with three bone is that it doesn’t have only one solution; it has an infinity of solutions (uniess you can also add more constraints.)

You might calculate backwards from the toes, “planting” the heel where you want it, and then run two-bone on thigh and shin bones to go from hip socket to desired heel location?

FABRIK will solve >2 bone chains decently.

Hey Thanks guys. I might go back and try fabrik. I’m actually on to something that’s gotten me 95% there based on what jwatte said about calculating backwards. In the anim graph I’m getting the socket location for the foot and the toe. I’m subtracting the toe location from the foot location. So as the heel raises in the animation I have a vector that goes up and forward. I’m adding that vector to my predicted IK point and BAAMM!! the toe is staying in place. Granted this is just in my testing area but it’s still working.

I had such an evil maniacal laugh when it started working I might have scared my office mates.