3-Bone Limbs

3-bone limbs (available from Limber v2.1) have two bends instead of one. They're primarily designed for rigging animal and insect legs, but you can also use them to rig humanoid legs with foot roll, arms with articulated shoulders, fingers, tails, torsos and pretty much anything that needs to bend back on itself in a Z shape, or curl up in a C shape.

Limber handles 3-bone limbs completely separately to 2-bone limbs - you can't turn one type into the other, or copy and paste between them. Otherwise, the workflow is the same and most of the differences between 2- and 3-bone limbs are obvious: 3-bone limbs have three sections (Upper, Middle and Lower) instead of two, two joints (Upper and Lower) instead of one, and so on.

The main difference between 2- and 3-bone limbs is how they work in IK Mode. As well as the familiar Clockwise, Stretch and Anti-pop controls, 3-bone limbs have five Weight properties unique to them.

When Shape is set to Z Shape, the lower joint doubles back on the upper, while in a C Shape limb, both joints bend in the same direction, eg. Clockwise.

Other differences to 2-bone Limbs

Adding Art

Hold Shift to Add Art to the Middle section of a 3-bone limb. Otherwise, it's the same process as for 2-bone limbs: it will be added to the limb's Lower section by default, or the Upper section if you hold Option / Alt.

FreeK Mode

When you add FreeK controllers to a 3-bone limb, you'll always have two of them - one for each joint. FreeK can only be dialled up and down for both FreeK controllers at once - so you can't use FreeK on one joint and not on the other.

Matching

When matching IK for a 3-bone limb, the default behaviour is to provide an approximate match instead the usual perfect match.