Giving An Object Control Structures
Rigging is the process of giving an object control structures to animate it. There are several
ways of doing that and depending on the needs and the object the most suitable has to be
chosen.
Armatures
Armatures are similar to bones in the human body. An armature can be added like an object.
Then it needs to be linked to the object it should deform through an armature modifier. The
deformation is based on moving the vertices, thus it is important to have vertices at the key
positions where the object needs to be bent. It is also possible to restrict the effect of a bone
to a vertex group. For an armature three different modes exist.
Object Mode
The first one is the object
mode, where the armature is placed in the right position and scaled to make it the easiest to
animate.
Edit Mode
Edit mode is where an armature can be extruded, which makes it possible to construct
an entire skeleton. Thus armatures are always used to animate body motions.
Pose Mode
The last mode is the pose mode, this is the mode where changes on the armature (rotating, scaling,
etc.) cause the object to deform.
Weight Paint
To make smooth motions possible one has to weight paint the deformed object.
A weight paint value of one (red) means that this part of the object completely follows the bone.
On the other hand a value of zero (blue) lets the bone not at all have an effect on the object.
Shape Keys
As its name indicates shape keys are savings of shapes. That means that the position of vertices
can be stored. By adding a shape key for the first time the current shape is saved as the
base-shape of the object. When further shape keys are added, the object at first does not
change, because every added shape key is initially a copy of the base. Then the object can be
manipulated.
Shape Key Driver
To animate shape keys it is necessary to add a driver. That is an object which changes in
scale, rotation or position, affecting the value of the shape key. A value of zero means there
is no effect and a value of one means the current key is fully applied. All the intermediate
steps are interpolated by Blender.
Lattice
Another method to deform an object is to
use a lattice. In principle it is a
surrounding low-vertex box, which deformation
causes the linked object to deform.
So it gets possible to easily modify an object
with even more than one thousand vertices
only by changing an object with eight vertices.
The deformation may also be restricted to certain vertex groups.