This book is about algorithms that create synthetic images fast enough that the viewer can interact with a virtual environment. We have focused on three-dimensional rendering and, to a limited extent, on the mechanics of user interaction. Modeling, animation, and many other areas are important to the process of making a real-time application, but these topics are beyond the scope of this book.We expect you to have some basic understanding of computer graphics before reading this book, as well as knowledge of computer science and programming. We also focus on algorithms, not APIs. Many texts are available on these other subjects. If some section does lose you, skim on through or look at the references. We believe that the most valuable service we can provide you is a realization of what you yet do not know about—a basic kernel of an idea, a sense of what others have discovered about it, and ways to learn more, if you wish.We make a point of referencing relevant material as possible, as well as providing a summary of further reading and resources at the end of most chapters. In prior editions we cited nearly everything we felt had relevant information. Here we are more a guidebook than an encyclopedia, as the field has far outgrown exhaustive (and exhausting) lists of all possible variations of a given technique. We believe you are better served by describing only a few representative schemes of many, by replacing original sources with newer, broader overviews, and by relying on you, the reader, to pursue more information from the references cited.