Advanced Methods in Computer Graphics

structure, not a graphics primitive. A bone essentially stores information about its position and orientation relative to its parent in the skeleton. Every bone is given a unique index as shown in Fig. 4.5b. Vertices belonging to a group are associated with a bone using the bone’s index. The part of a mesh represented by a bone is called its skin. In the example given in Fig. 4.5, the skin of bone “8” is the mesh segment that belongs to the set LUL. Two simple ways of associating groups of vertices with bones are shown in Fig. 4.6. In the first method, every entry in the vertex list is appended with a bone index. This method is suitable when vertices need to be associated with more than one bone (we will discuss this 4.4 Vertex Skinning 59 process later in Sect. 4.6). If several consecutive entries in the vertex list have the same bone index, then the second method is preferred where the minimum and maximum indices of a range of vertices are stored against a bone index.