Acknowledgments Joep and I would like to acknowledge Steffen Roemer at Mental Images for keeping us on the straight and narrow technical path in regards to mental ray. Also, we'd like to thank Chris Simpson and his staff at Focal Press for all the help in turning the pages we generate into a real book. Wrangling one author through the process of producing a book is difficult, but having two authors makes it three times as hard. Mostly, we thank you, the reader, for having enough confidence in Joep and me to purchase the book. Dedication Ted Boardman would like to dedicate this book to Sally Turner for over 30 years of companionship.