This chapter discusses the motor system of the artificial fish (see Fig. ). In particular, we describe the physics-based fish model and how it achieves locomotion. The biomechanical model we develop is simple, but it is nonetheless effective for realistically animating fish locomotion. We start by presenting the structure of the dynamic fish model, then introduce the dynamics of this model and the simulated aquatic environment. The numerical method employed for solving the differential equations of motion of the fish model is discussed next. Subsequently we describe the biomechanics-based modeling and control of the fish's locomotion, paying special attention to the construction of the motor controllers. This includes the abstraction of the muscle movements for useful locomotion and the functional modeling of the pectoral fins.

**Figure:** The motor system of an artificial fish.

Xiaoyuan Tu | January 1996 |