IK Twisting! And it's driving me NUTS!

[george-tasick]

I'm building my first character with Maya and after I put in the standard bipedal bone setup, I put the IK on the arms and legs but then when I move them toward the torso they twist about 100 degrees inward at the hip and upward at the shoulder before the foot/hand even gets past the opposite knee or where the elbow was!

The problem seems rather random as sometimes it doesn't happen and the limb works properly but after 2 weeks of trying to figure it out I still have yet to get a character with 4 properly working limbs at the same time.

After second guessing myself thinking it was my own error I was assured by my instructor that I had everything setup properly and that he had rarely seen this problem with Maya's IK. I was told to setup a pole vector constraint but that still didn't solve the problem and after tinkering with some settings he was drawing a blank.

I have worked on this model at 2 different computers and with 2 different copies (same version, 4.0) of Maya and the problem remains consistent.

Has anyone ever seen this before and more importantly does anyone know how to fix it? This IK oddity is driving me nuts and I think I am going to punch through my screen and beat the crap out of my bone structure!

[badcookie]

its not all that uncommon

a lot of the problem is the positioning of your joints. if they are slightly twisted themselves (as in a bow legged person) then they are more likely to twist.
after building them at slight angles (the angle which you want it to bend) and freezing transforms, run the joint orient script to make all the local axis point down the bone. then right click on them and set perferred angle. then skin, then make a PV constraint. however if you need the bow leg, then instead of translating the knee joint over, and then the ankle joint back, ROTATE the hip joint, and the knee joint back, and in that case don't freeze those transforms, but follow each of the other steps.

hope this helps.

[palodich]

This sounds more like pole vector/twist disc situation. Use the manipulator tool to animate the pole vector/twist disc. Adding a null object in front of the knees or behind the elbow and making it a pole vector constraint can solve a lot of problems without animating.

[gnimmel]

Just a thought, did you limit any of the joints rotations? i.e. the elbow and knee can only bend on one axis so you need to lock the other 2. Did you also set the prefered position of the joints? This helps in some cases when IK messes up.

Richard