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Reviewer: William Ward Armstrong

The software simulation system described in this book provides a synthetic, simulated human for use by designers, human factors engineers, animators, and others who need to study the kinematics or dynamics of human motion. At the lowest level of control, the human figure, called “Jack” like the system itself, can have its body and limbs placed in various positions in relation to an environment, say for studying the visibility of an instrument panel. At the highest level (not yet completed), the goal is to be able to instruct Jack to perform motions that involve bodily dynamics without giving detailed descriptions of how tasks are to be done. The book is both entertaining and informative. One can read it for a general overview, while noting the wealth of detail available for specific topics. The authors have made good decisions about the level of detail. For example, a simple motion like bending the torso while maintaining balance is neatly illustrated by a sequence of figures. Some detail of how this motion is executed is provided. Of course, the motion is artificial, since dynamically controlling the balance of a realistic human model is still far beyond the state of the art. When I had a question about inverse kinematics in the area of medical rehabilitation, the book turned out to have a useful discussion about nonlinear programming as a tool for inversion. In sum, the book provides a solid stepping stone to further progress. After motivating the need for human models, the authors turn to the forms of modeling of body parts, their articulation, and their motions. Next come ways of controlling the model, including inverse kinematics. Constraints that specify a pose are treated with nonlinear programming techniques. Behaviors are described that allow parts of a motion to be derived automatically. Simulation with “societies of behaviors” is introduced, including a section on dynamic control. The question of collision avoidance is raised, taking the book into the realm of posture planning. Finally, task-level specification is discussed. It is not necessary to have the Jack software to benefit from reading the book, but it is necessary if one wants to apply the book's techniques to real problems. The Jack software runs on Silicon Graphics workstations. According to Badler, the software is available for a license fee through the Center for Human Modeling and Simulation at the University of Pennsylvania.