Animating 3-Bone Limbs

Animating 3-bone limbs on FK or FreeK is very similar to animating 2-bone limbs. But in IK Mode a 3-bone limb has more options than a 2-bone limb.

When a 3-bone limb's Weight property is zero, the angles of the two joints will be equal to one another, and the other Weight properties have no effect at all. This 'Zero Weight' is the simplest way to animate with 3-bone limbs and the experience feels closest to animating 2-bone limbs.

All of the animations on this page use Zero Weight, Z shape limbs for their back legs.

All four legs have Zero Weight, so the two internal angles of each leg are always equal.

Weight properties

The Weight properties (Weight, Weighted Section, Weight Direction and Lockout) allow you to take more control over the shape of the limb, without leaving IK mode.

As you dial up Weight, the Weighted Section (Upper or Lower) changes angle, until it points towards the Weight Direction angle. When Weight is 100%, the Weighted Section has a fixed angle, permanently pointing in the Weight Direction.

When you're animating a character, you can use the Weight properties to set poses that you can't get with Zero Weight. Most likely, you'll need to keyframe Weight, Weight Direction or both. Here are two examples:

This dog's front legs have Weight set to a constant 70%, whilst the Weight Direction is keyframed, so the paw can bend backwards when it's in contact with the ground:

This fox, on the other hand, has fixed Weight Direction and keyframed Weight:

You can download all the animations on this page (and every other character rig we have the rights to give you) and check out the keyframes yourself, right here.

Lockout

Lockout is designed to make it easier to animate the front legs of horses, cows, deer, sheep and other ungulates - animals with hooves. These animals tend to have less flexible front legs that visibly 'lockout' when they are loaded with the weight of the animal's body.

The bull's leg locks straight when it's body weight is loaded onto it.

If you enable the Lockout checkbox, the Weight Direction angle is completely overridden, and instead, as you increase Weight, the Weighted Section becomes the same angle as the Middle section, forming a straight line.

By turning up lockout weight when the foot contacts the ground, it's easier to maintain a locked, straight leg, and avoid snapping and sudden kicks.

The front legs were animated using Lockout, to ensure the middle and lower sections can straighten without the upper section also having to.