Welcome to CAT's IK. It's probably the worst IK system imaginable. You can try turning on the Up Vector, which might help stabilize the leg. Select the leg and go to the Modify Panel and look for a button labeled Use Up Node. This will create a helper at the knee position, which you can use to point he knee with. I've…
It's not so much the IK as ALL OF IT. :) It might be a nice animation system, but I don't know because I can't get it to not crash. I'm not joking when I say it crashed on me when making the allosaurus preset to look into this problem. We evaluate it as an option with each Max release, but we haven't gotten past the…
Thanks for sharing the file! I managed to get it pretty stable using a Up Node and tweaking the timing of your anim. One thing I noticed in your animation though was that you had the leg extended beyond the IK length, which is never good, so watch out for that. There were also a few frames that just seemed bad, like frame…
Yeah CAT IK is rather dodgey it seems. I'm using a custom rig which you can download here: https://docs.google.com/folder/d/0ByW_jeNayjiVUkFGb096YzVNRzQ/edit?usp=sharing Also e_x I tried what you said and it's still playing up unfortunately. If I can't get this working, what would you suggest I use instead? I'm using BIPED…