Shin Twist with Biped

[thefatninja]

I am rigging my character to the biped created from the biped guide. I like all the rig except that my shin bone rotates causing the calf to twist in. Is there a way I can fix this?

[paulrus]

Have you gone in and adjusted all your weights? It looks like it's got some weights pointed towards the other leg.

[ThE_JacO]

If you look at the shin orientation it's actually changing between the two poses, so while mis-weighting might be adding some deformations, it does look like a transform problem on the rig rather than weight problem on the deformer.

You can sort it out by making sure the bone's roll is unaffected, and eventually the upvectoring of the chain, I'd look into those two things first.

[thefatninja]

I shin bone is rotating. How do I stop it from rotating? Sorry for the beginner question

[ThE_JacO]

As I said look into upvectoring first and foremost, and make sure you explore and learn both what bone and chain properties do.
CTRL+R for chain, and CTRL+K for the kine of the bone (enter for just the bone iteself) will get you all the panel love you need to look into.

Make sure there's nothing odd going on with the bone rolling and that there are no redundant or odd keys or ik/fk blends on it.

If you're going through a bit of a learning process that's what you want to start looking into, it won't hurt regardless of whether it will solve your problem or not :)

[3DMastermind]

Yes like Raf suggested it is up-vector related.
2D IK bones are "planar" so simply align the up-vector (move the little pyramids behind the legs).
When moving any effector you must also adjust this up-vector to adjust the roll on the ik chain ;)