This database provides models for bones, mechanical joints between them, ligaments, skin, and muscles. Muscles include attachments and actions lines. Attachments are the area where muscles are bound or connected to the bones. Together with the origin and insertion attachments classically considered by anatomy, we model also the areas on bones which constrain the mechanical action of some specific muscles. These are called the guides .
Action lines model the lines along which link spindles act.
Each action line is a polyline getting from an origin to an insertion attachment, possibly through any number of guides. Tendons in our case are considered as being part of the muscle. Figure 7 demonstrates the definition of action lines and the respective attachments. Joints are also modeled to specify the mechanical dependency or constraint between bones. Figure 8 shows how a joint is defined in terms of the transformations between the two bones.