Manipulating Bones

You can create an armature by pressing Shift + A in Object Mode and selecting Armature > Single Bone. If you want to create a skeleton from the default bone in the armature, you’ll have to do that in Edit Mode (Tab) using the techniques you’ll see in a moment. In Figure 11.1, you can see the elements of a bone.

Figure 11.1 The elements of a bone

When you have a series of bones connected in a line it’s called a chain. A bone’s direction goes from its head to its tail and that’s important because it defines the bone chain’s direction as well. A bone connected to the tail of another bone will follow the movements of the latter (it will be the latter bone’s child). You will learn more about this later on.

The list that follows describes shortcuts and controls that will help you work with bones in Edit Mode:

Select bones with RMB and move, rotate, and scale them the same way you do with any other element in Blender (G, R, and S). Bones are made of the bone itself and “spheres” at its top and bottom, which are the bone’s head and tail (these could be called joints in other software). You can transform the whole bone, or just the head or tail, to adapt it to the shape you need.

To create a chain of bones, you can select the tail of a bone and extrude it with E, or use Ctrl + LMB in the location where you want the new bone to end, just as if you were extruding vertices. When you extrude a bone from the tail of another, the new one will be a child of the existing bone. However, if you extrude from the head, Blender will just create a new bone, with no parenting applied to it.

In the Tools Region, you can activate the option X-Axis Mirror in the Armature Options panel. If you make changes to one part of the skeleton’s X-axis, those changes will be mirrored to the other side of the skeleton on that axis. To use this option properly, select the tail of a bone that is situated in the middle of the X-axis (the mirror plane) and press Shift + E to extrude toward the sides (this will create a first mirrored extrusion). After that first extrusion, you can keep extruding and transforming the bones from that bone chain and they will be mirrored to the other side of the axis.

You can duplicate bones by selecting them and pressing Shift + D.

You can create new bones at the 3D cursor position pressing Shift + A.

You can name bones in the Properties Region, in the Item panel. Keep in mind that for armatures you’ll have two fields: one for the armature’s name and another for the bone’s name inside that armature. Alternatively, if you look at the Properties Editor, you’ll notice that the tabs are now slightly different: you have the Object tab, the Constraints tab, the Armature tab, and the Bone tab. When naming the selected bone, make sure to go to the Bone tab; otherwise, you’ll be renaming the armature itself (the object that contains all the bones).

In Edit Mode, you can define the bones’ hierarchy. Select the bones you want to be the children (the bones that will follow the parent), and then select the bone you want to act as the parent. Press Ctrl + P and you’ll see two options: Connected will join the tail of the parent with the head of the children, while Keep Offset will parent all the selected bones and keep them disconnected. To remove a parenting, select the object you want to “set free,” press Alt + P, and you’ll have two options: Clear Parent will completely remove the relationship with the selected bone’s parent bone, while Disconnect will separate the head of one bone from the tail of the other, but the parent relationship will still be there.

If you select one or more bones, you can “roll” the selection with Ctrl + R to control its orientation. Ctrl + N displays a pop-up list with several predefined options for automatically orienting bones (such as aligning them to the orientation of the active bone or orienting them to look at the 3D cursor).

If you select two bone ends (heads or tails) and press F, a new bone will be created to fill the gap between the two tips, similar to the operation for creating an edge to connect two vertices in a mesh. Keep in mind that only the new bone’s head will be connected to its parent. The new bone’s tail will be free and you’ll have to parent it with the next bone in the chain if you need to connect them.

If you select one or more bones, if you press W, you’ll access the Specials menu. One of its options is Subdivide, which will divide longer bones into shorter ones. From the Operator panel in the Tools Region, you can set the number of divisions.

You can select two connected bones and merge them into a single one by pressing Alt + M.

If you want a chain of bones to parent in the opposite direction, you can switch the direction of a bone with Alt + F. This basically switches the head and tail of a bone, changing the direction of the hierarchy.

If you have bones in your skeleton you want to remove, delete them by pressing X.

As always, you can hide and unhide bones with H and Alt + H to display only the ones you’re working with, or to hide any bones that are in your way.