Rendering is the process of producing an image from the description of a 3D scene. Obviously, this is a broad task, and there are many ways to approach it. Physically based techniques attempt to simulate reality; that is, they use principles of physics to model the interaction of light and matter. While a physically based approach may seem to be the most obvious way to approach rendering, it has only been widely adopted in practice over the past 15 or so years.
This book describes pbrt, a physically based rendering system based on the ray-tracing algorithm. It is capable of rendering realistic images of complex scenes such as the one shown in Figure 1.1. (Other than a few exceptions in this chapter that are noted with their appearance, all the images in this book are rendered with pbrt.)
Most computer graphics books present algorithms and theory, sometimes combined with snippets of code. In contrast, this book couples the theory with a complete implementation of a fully functional rendering system. Furthermore, the full source code of the system is available under an open-source license, and the full text of this book is freely available online at pbr-book.org/4ed, as of November 1, 2023. Further information, including example scenes and additional information about pbrt, can be found on the website, pbrt.org.