process called skinning. In the most common case of a polygonal mesh character, the bone is associated with a group of vertices; for example, in a model of a human being, the bone for the thigh would be associated with the vertices making up the polygons in the model's thigh. Portions of the character's skin can normally be associated with multiple bones, each one having a scaling factors called vertex weights, or blend weights. The movement of skin near the joints of two bones, can therefore be influenced by both bones. In most state-of-the-art graphical engines, the skinning process is done on the GPU thanks to a shader program. For a polygonal mesh, each vertex can have a blend weight for each bone. To calculate the final position of the vertex, a transformation matrix is created for each bone which, when applied to the vertex, first puts the vertex in bone space then puts it back into mesh space. After applying a matrix to the vertex, it is scaled by its corresponding weight. This algorithm is called matrix-palette skinning or linear-blend skinning, because the set of bone transformations (stored as transform matrices) form a palette for the skin vertex to choose from. Benefits and drawbacks Strengths A bone represents a set of vertices (or some other object which represents something, such as a leg), The animator needs to control fewer characteristics of the model, The animator can focus on the large-scale motion, Bones are independently movable. An animation can be defined by simple movements of the bones, instead of vertex by vertex (in the case of a polygonal mesh). Weaknesses A bone does only represent a set of vertices (or some other precisely defined object), and is not more abstract or conceptual. Does not provide realistic muscle movement and skin motion. Possible solutions to this problem: Special muscle controllers attached to the bones. Consultation with physiology experts, to increase accuracy of musculoskeletal realism with more thorough virtual anatomy simulations. Applications Skeletal animation is the standard way to animate characters or mechanical objects for a prolonged period of time (usually over 100 frames). It is commonly used by video game artists and in the movie industry, and can also be applied to mechanical objects and any other object made up of rigid elements and joints. Performance capture (or motion capture) can speed up development time of skeletal animation, as well as