Advances in the field of computer vision are leading to radical changes in the way we interact with computers. At the time of this book's publication in 1998, it would soon be possible to enable a computer linked to a video camera to detect the presence of users, track faces, arms and hands in real time, and analyse expressions and gestures. The implications for interface design are immense and are expected to have major repercussions for all areas where computers are used, from the work place to recreation. This book collects the ideas and algorithms from the world's leading scientists, offering a glimpse of the radical changes that are round the corner and which will change the way we will interact with computers in the near future.