View Full Version : IK help

11-02-2004, 05:59 AM
I decided to start learning to animate since I've been doing modelling for awhile now,
Im trying to learn how IK works, i have a little set up here but i can't figure out how to make the leg bend, i will attach the scene file so you can see, I've looked at alot of IK tutorials and still no idea, thanks for replies


11-02-2004, 09:51 AM
Things you must doo to get IK to work:

1/ For the end of the IK chain (for example the Foot) you must select an IK 'Goal Object', usually using the Motion Options Panel(press 'm' with the end object selected). Optional: Set Match Goal Orientation if you want the goal object to control the rotation of your end object. Optional: Set 'Full-time IK' to on if you want to control your chain with just IK, otherwise you will have to pose with IK, then select the chain objects and keyframe them.

2/Select each object in your IK chain that you want to be affected with IK (note: this doesn't have to include the end object or every object in the chain!) and go to the Controllers and Limits tab of the Motion Options panel. Change one or more of the channels Controller drop down to Inverse Kinematics (note: you don't have to have every channel controlled by IK, the point is to just apply IK to those objects which need it on just the channels which need it, like a knee joint would have it on the Pitch channel, and hip joint would have it on the Heading and Pitch)

3/ Pre-bend your chain. That is, when you make your bones or whatever, make sure there is a slight bend in the chain, like the knee for example. LW will then tend to bend the chain in that direction. If the chain is straight, LW may flip back and forth as it isn't sure which way to bend the chain.

4/ Ensure IK is enabled. You can toggle this on or off with shift-F8.

5/Optional: For the object above the chain (where you want the IK to stop) enable 'Unaffected by IK of descendants' in the motion panel. This speeds up calculations.

11-02-2004, 05:30 PM
thanks Dodgy

I done all of that, but the knee still doesnt bend, The dotted line going to the goal object is coming from the knee, shouldn't that be coming from the end of the leg?

11-02-2004, 10:42 PM
Yes. Did you select the foot object and set IT's goal to the Ik object? Cause this sounds like the the knee/calf is the end of the IK chain. Change it's goal to <none> and the goal of the child object to your ik object.

11-02-2004, 11:37 PM
hrmmm, i was just making a stick man with no feet, the leg is just two 2 point polys, and bottom 2 point poly (from knee down) is the one using the goal object, i can't do it like that?

11-02-2004, 11:57 PM
The items in your IK chain have to be separate objects or bones set up in a parent-child heirarchy ie. foot bone connected to the shin bone connected to the thigh bone etc etc.
You have to apply IK to the proper channels of each item. To create a leg that bends at the knee you need a minimum of 3 bones for example: A thigh bone, shin bone and an ankle bone . The anke bone would be the END EFFECTOR. Thats the bone that is attached to a GOAL OBJECT. The goal object is the handle that controls the leg. :)

11-03-2004, 12:07 AM
ahhh, u need a minimum of 3 bones, thanks splinegod
i think that would be the reason, ill try it out

11-03-2004, 06:50 AM
yep! that was the reason, only had 2 bones
thanks heaps SplineGod!