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the Armature and its Features

In this image, the selected verts will belong to the bone they surround

In Blender, skeletons are known as Armature Objects. Armatures are actually nothing like real-life skeletons. The best way to think of a bone in Computer Graphics (CG), is to imagine it as a center about which the vertices of a mesh can exist as children.

The Blender armature object is a container for sub-objects, called bones. We're going to tour through all the features of the armature object, and you can try them as we go along. You can add an armature the same way you add any other object in Blender, through the Space menu. Any time you add an object to a scene, you should consider clearing it's rotation with AltR while in object mode.

the Armature and its Work Modes

Armatures have an object mode and an edit mode, just like the Mesh Object(link), and you can toggle these with ⇆ Tab, just like a mesh object. The state that you see your armature in while in edit mode is known as the Rest Position. Armatures are meant to be animated, so to fullfill this purpose, they have yet another mode: Pose Mode. You can toggle pose mode by pressing Ctrl⇆ Tab. Pose mode is different from edit mode in that you can change the selection to other objects outside the armature without first leaving pose mode. If you do change selection, when you return to select the armature, you will still be in pose mode. Bone selection is preserved when changing between edit and pose mode. You are placed into edit mode when a new armature is added to a scene, just like mesh, curve, and surface objects.

Armature Edit Mode

Bones are manipulated as pairs of points while in edit mode

Edit mode is where you add, remove, and place bones. In edit mode, bones are placed by moving points. Each bone has two points, a root and a tip. A new armature object has one bone by default, but more can be added via the Space menu, or you can select the tip of any existing bone and extrude(link) a new one from it with the E key, or CtrlLMB Template-LMB.png click (not drag, that would do lasso select) in the 3D view. You can see the number of bones and bone points displayed in the top header. Extruding creates a bone that is a child of the bone from which it was extruded, and gives these two bones the special relationship of being connected. You can change this by toggling the Con button in the Armature Bones buttons panel while you have the bone in question selected.

Armature Object Mode

Bad things happen when an armature or it's mesh are transformed relative to each other

In object mode, an armature will behave just like any other singular 3D object (even though it may contain multiple bones, which are objects themselves). Armatures can be moved about, resized, and rotated. It is good practice not to perform transformations on armatures. For armatures to deform a mesh object properly, the location, orientation, and size of the mesh (relative to the armature) must stay constant. The only way to ensure this is to constrain the mesh object's location, rotation, and size to the armature object. To make the mesh deformed by the armature, either make it a child of the armature, or use a modifier. Modifiers have more helpful features, so their use is the preferred method.

Armature Pose Mode

Pose mode is the mode where posing and animating of the armature bones can be done. Bones are technically sub-objects of the armature. The total number of bones, and number of selected bones is displayed in the top header. Besides posing and animating, you can also create and manage constraints for bones in pose mode. In edit mode, you define your armature's rest position. In pose mode, when you clear all bones of transformations (AltR, AltS, AltG), the rest position is what you should have, assuming you don't have any constraints preventing your bones from returning to the rest position. You can also make objects outside the armature children of a bone, by selecting the object with CtrlLMB Template-LMB.png, and then parenting it to a bone with CtrlP.

Building an Armature/Rig: Construction Techniques

Knowing how to add and move bones isn't everything you need to know to build an armature rig. A lot of work with armatures is done with ⇧ ShiftS snapping, and cursor-as-pivot operations. You should understand the difference between using the Bounding Box Center as the pivot point (,), and using the 3D Cursor as the pivot point (.). Throughout the rig tutorials in this section you will be required to do a lot of different snapping and cursor-pivoting operations.

Placing a New Bone



Often a new bone needs to be added in the same location as an existing root or tip point. To do this, snap the cursor to the existing point and add a new bone with the Space menu.

You can also place a new bone exactly halfway between two other bones. To do this, select the root points of two existing bones and snap the cursor to them both. It will then be halfway between them, and you can then add the new bone.

Resizing a Bone

Snapage4.jpg Snapage5.jpg

There are two ways to resize a bone. The easy way is to select the root and tip points, snap the cursor to the selection, and then snap the tip point to the cursor. This makes the bone half as long as it was to begin with. In the tutorials, when you read, "resize the bone to 50%", this is what you want to do. If you see "resize to 25%", then just do this twice.

The other way is to snap the cursor to the root point, set the cursor as the pivot point, and then scale the tip toward or away from the cursor. This method allows you to make the bone any percentage of it's original size.

Pointing One Bone at Another Bone


A lot of the rig designs require one bone to track (point at) another bone. This means that the bone that does the tracking needs to be pointing exactly at the target bone. To do this, you snap the cursor to the root points of both bones, and then snap the tip of the tracking bone to the cursor.

Armatures and Buttons

Many features for armatures and bones are accessible through the buttons window. Pictured below, are two panels from the editing buttons (F9). The Armature Bones panel changes based on a number of factors which include:

  • The armature's current mode
  • The bone or bones that are selected
  • The status of the selected bone as part of an IK chain or not.
These affect all bones of the armature
These buttons affect the currently selected bones

The Armature Panel


Editing Options

  • X-Axis Mirror: Enables mirrored editing for all mirrored bones. Use ⇧ ShiftE to make mirrored extrusions, when X-Axis Mirror is active.
  • X-Ray: Causes the armature to be drawn in the scene last, making it visible through all other objects, except for other objects that are also X-Ray active (see Draw Panel(link)).
  • Auto IK: This is a new feature and is still fairly undeveloped at this point. Automatic IK allows you to pose an armature by clicking and draging on any bone. Auto IK generally doesn't work with rigs, and should mostly be used as a posing tool for FK armatures.
  • Ghost: Enables ghost drawing, which is visible if the bones are animated. The number here is the number of ghost copies Blender will draw. (In newer versions of Blender, this option seems to have been moved to a tab right next to "Armatures" called "Visualizations" (only visible in pose mode) where you will see the Ghost option.
  • Step: The number here is the number of frames between ghost copies.

Display Options

  • Bone Layers:abc These work in the same manner as the world layer buttons. Each button represents a layer, and when active, that layer is visible. Bone layers are a setting that is local to each armature.
  • Display Modes:abc These buttons set the armature display mode.
  • Draw Axes: Enables axis drawing for all bones of the armature.
  • Draw Names: Enables drawing of bone names in the 3D view.

Deform Options:

  • Vertex Groups: Enables bones to deform a mesh via vertex groups.
  • Envelopes: Enables bones to deform a mesh via envelopes.
  • Rest Position: Forces the armature into rest position while in pose mode.
  • Delay Deform: Disables deformation of children mesh objects.

The Armature Bones Panel


Selected Bones

  • BO: The name of the bone shows here. You can also use the Transform Properties panel in the 3D view (N).
  • Dist: The envelope distance shows here. It is expressed in units from the surface of the bone (in envelope mode) to the outside of the envelope field.
  • Weight: The weight that is used to calculate vertex influence amounts when using envelopes.

  • Segm: The number of b-bone segments.
  • In: The blend-in value. Affects the shape of the b-bone bezier curve.
  • Out: The blend-out value. Affects the shape of the b-bone bezier curve.

  • Hinge: This option allows bones to defy the rules of the parent/child relationship. When enabled, this feature causes bones to keep the appropriate location according to the parent's coordinate system, but not size and rotation.
  • Deform: Enables bones to affect mesh vertices. Also includes bones for consideration during automatic vertex group creation.
  • Mult: Causes vertex group weights to be multiplied by envelope weight. When enabled, a weight of 0 assigned to some verts will cause them to be unaffected by the envelope.
  • OB: Specifies another object to be used as the visible bone geometry.

  • Bone Layers: abc Indicates which layers this bone belongs to.

These buttons only appear for bones that are part of an IK chain:

  • Lock Axis Rot: Allows you to prevent the bone from rotating on a specified axis.
  • Stiff: Values for resistance to rotation.
  • Limit Axis: Gives access to DoF (Degrees of Freedom). Allows minimum and maximum rotation values to be specified.

  • Stretch: Allows bones to scale bigger or smaller in response to IK effector movement.

The Armature Display Modes

These bones are actually identical, just using different representations Here you see three identical armatures, each with only three bones

Armatures have four different methods of graphically representing bones, called Display Modes. Each display mode is only a different method of representing an armature. No matter which mode you use, no changes are made to the bones or the armature.

However, some display modes do give you access to bone properties and special visualizations that the other display modes don't.

Octahedron This is the classic display mode for bones. Before the other draw types existed, this is how bones looked (and it's a very professional looking way to draw them).

B-Bones The B-Bones display mode shows the shape that bones take when segmented (while in pose mode).

Stick For animators, this mode is perfect, because the bone objects don't hog a bunch of screen space which is better used for drawing the character. After all, it's the character that is being animated.

Envelopes The Envelopes display mode shows the influence areas of the selected bones.

Moving the Mesh

Armatures are pretty useless if they don't move the parts of our mesh that makeup our characters. There are two ways to do this in Blender:

  • Vertex Groups: Vertices are assigned to groups with names. All verts in a group are affected by a bone with the same name as the vertex group (assuming the armature is assigned to affect the mesh, by way of parenting or modifier).
  • Bone Envelopes: All verts that reside within the limits of a bone's envelope field are affected by the bone (assuming the armature is assigned to affect the mesh, by way of parenting or modifier).

Armatures and Hotkeys

Here are some of the hotkeys for working with bones in edit and pose mode. Some keys may not be listed, such as ⇧ ShiftD, which duplicates a bone in edit mode. It can be assumed that ⇧ ShiftD duplicates bones since it duplicates other types of objects, and Blender typically uses the same key for the same functions, even if the objects or modes are different.

Edit Mode

  • CtrlN: Recalculates the bone roll angles.
  • CtrlP: Makes the selected bone the child of the selected active bone.
  • W: Opens a menu to either rename bones to the suffix of the opposite side, or to subdivide the currently selected bones (suffix mirroring works on duplicated bones, which will have a number suffix after the L/R suffix).
  • M: Opens a menu of options to mirror the selected bones.
  • L: Selects all bones connected to the bone currently under the mouse arrow.
  • AltS: In b-bone display mode, this scales the size of the display thickness. In envelope display mode, it changes the outer envelope size (the Dist value from the Armature Bones panel).

Pose Mode

  • CtrlAltC: Give a constraint to the active bone, targeting one other selected bone.
  • ⇧ ShiftI: Give an IK Solver constraint to the active selected bone, targeting the other selected bone.
  • CtrlC: Opens a menu to copy attributes of the selected active bone, to all other selected bones.
  • M: Opens a menu of options to mirror the selected bones.
  • L: Selects all bones connected to the bone currently under the mouse arrow.
  • AltS: In b-bone display mode, this scales the size of the display thickness. In envelope display mode, it changes the outer envelope size (the Dist value from the Armature Bones panel).

--Wavez 08:41, 27 July 2006 (CEST)