View Full Version : Ik Handle Problem

09 September 2003, 06:43 PM
I'm getting some wierd twitching going on with my IK handle when I move it around. It is very subtle, but is noticable, and will cause probelms in animation.
I'm using an FK/IK set-up, with a blend colors node, driving the switch. Any thoughts?

09 September 2003, 03:41 AM
I'm replying to my own post here, just in case someone else gets an issue like I was having.

The think the basic problem is the joint Orient values. I'm not sure if what I did is an absolute solution, but it's working for me in my situation. Basically, me and another guy made an automated rig based off of locators. I Position the locators and then you have a base set of joints. Then I call a few procedures, which duplicate some joints for FK/IK, and then build my rig based off of a models position. What I did to fix my problem was to position the locators in a straight axis in the front view (Maya), before I build my rig. Then I orient my joints, then through a procedure to put back the joints in the correct position of the model, I then created my rig. This made my IK a lot more stable. In the initial script my joints were oriented great, but I found that my joint Orient values were a little messy.
Anyways, this was just in case anyone gets into the same problem I was having. I hope it helps.

If what i said didn't make a whole lot of sense, let me know

09 September 2003, 08:18 AM
this is happening because Maya does not understand what your IK chains preferred angle is. Setting the preferred angles can assure smoother motion during IK posing and animation.

In a skeleton, each joint's preferred angle indicates the preferred initial rotation of the joint during IK posing. When you build a skeleton, you should create the joints so that they are somewhat rotated into the angles you would want them to move into when they are animated. For example, when creating a leg, you should not create the joints so that they are all in a straight line. Rather, there should be a slight bend at the knee joint. This bend will be the joint's preferred angle for IK posing.

When you're done, and are ready to add IK, set the preferred angles for the skeleton. Even after you've rotated some joints, you can see what the preferred angles are by telling the skeleton to assume its preferred angles.

Hope that helps....



09 September 2003, 09:17 PM
I thought that was what was going on also, but that didn't help at all. What I did was not orient the joints in a straight line, but in a straight line in just the front view (just on one axis). They were still bent. Anyways, what I did fixed what was going on. Thanks DC.

09 September 2003, 12:45 AM
Well, one problem with making an automated rig is you cannot guarantee joint orient will be right based simply off of positions in xyz space. There's no way around it really. Do you orient your joints first, then move them into place? If so...that's bad....You should move them first, then reorient them so their rotation axis zero out properly. Once the joints are oriented properly, they should not be moved before you make the rest of your rig.

10 October 2003, 08:22 AM
about joint orient, u can arrange the joints in a line. but just after doing that, rotate the knee joint (let's say) in the way that u want to rotate and RMB and "Set Preffered Angle" and rotate the joint back.
about yours problem i think that the orientation of ur's joints and puppets/locators is not the same. (i suppose thet u did the snap to point thing alredy)

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