Inverse Kinematics (IK) is a simple tool that allows creating animations quickly and accurately. The first step to using IK is to add IK constraints and bones to your character, then you can use your IK bones to create animations easier. If you are having difficulty creating a walking animation, you should try it using these simple steps, and you'll find that it's much easier.
Rigging the Foot There are a lot of ways of going about rigging feet, so here I will just go over my favorite method. It doesn't give you any advanced foot roll functionality, but it is exceedingly simple to set up and use.
- Create your Foot IK bone. Select the back of the heel and extrude out a bone in edit mode. Name this bone "FootIK.L"
- Create your Knee Pole bone. Select the knee and extrude out a bone in front of it. Name this bone "KneePole.L"
- Select both of your new IK bones and press ctrl-P and click Clear Parent.
- In edit mode, select the foot bone, then shift select the foot IK bone, press ctrl-P, then select Keep Offset. This will make it very easy to control the foot as well as the leg with just the foot IK bone!
- Drag the knee pole bone out to be a few meters in front. The Knee will always point at the knee pole.
- Go into pose mode with your Armature selected.
- Select the bottom leg bone.
- Click the Bone Modifier tab and add the Inverse Kinematic bone modifier to the bottom leg bone.
- Choose a chain length of 2 (one for the shin, one for the thigh).
- In the Target field, choose your Armature.
- In the Bone field, choose your FootIK.L bone.
- In the Pole Target field, choose your Armature.
- In the Bone field, choose your KneePole.L bone.
- Adjust the Pole Angle such that your knee points at the KneePole.L bone. It is usually an exact multiple of 90.
Now redo the steps but for the right leg, and using ".R" instead of ".L" for the bone names.
Now you can create keyframes on your FootIK.L bone and the leg and foot will react accordingly! I have found that this reduces the time it takes to animate characters significantly. I'm animating characters for a game named Plague right now and I spent about 8 hours trying to make a sneaking animation and I just couldn't quite get it to look how I wanted. But then I learned how to rig up these IK bones just like this and I did it in about 10 minutes on the first try!
I hope this helped, feel free to contact me if you have any questions.