Skeletal animation or rigging is a technique in computer animation in which a character (or other articulated object) is represented in two parts: a surface representation used to draw the character (called the mesh or skin) and a hierarchical set of interconnected parts (called bones, and collectively forming the skeleton or rig), a virtual armature used to animate (pose and keyframe) the mesh. While this technique is often used to animate humans and other organic figures, it only serves to make the animation process more intuitive, and the same technique can be used to control the deformation of any object—such as a door, a spoon, a building, or a galaxy. When the animated object is more general than, for example, a humanoid character, the set of "bones" may not be hierarchical or interconnected, but simply represent a higher-level description of the motion of the part of mesh it is influencing. The technique was introduced in 1988 by Nadia Magnenat Thalmann, Richard Laperrière, and Daniel Thalmann. This technique is used in virtually all animation systems where simplified user interfaces allows animators to control often complex algorithms and a huge amount of geometry; most notably through inverse kinematics and other "goal-oriented" techniques. In principle, however, the intention of the technique is never to imitate real anatomy or physical processes, but only to control the deformation of the mesh data. Technique As described in an instructional article by Josh Petty: This technique constructs a series of bones (which need not correspond to any real-world anatomical feature), sometimes also referred to as rigging in the noun sense. Each bone has a three-dimensional transformation from the default bind pose (which includes its position, scale and orientation), and an optional parent bone. The bones therefore form a hierarchy. The full transform of a child node is the product of its parent transform and its own transform. So moving a thigh-bone will move the lower leg too. As the character is animated, the bones change their transformation over time, under the influence of some animation controller. A rig is generally composed of both forward kinematics and inverse kinematics parts that may interact with each other. Skeletal animation is referring to the forward kinematics part of the rig, where a complete set of bone configurations identifies a unique pose. Each bone in the skeleton is associated with some portion of the character's visual representation (the mesh) in a