Practical Global Illumination with Irradiance Caching (Synthesis Lectures on Computer Graphics and Animation)

ABSTRACT
Irradiance caching is a ray tracing-based technique for computing global illumination on diffuse surfaces.
Specifically, it addresses the computation of indirect illumination bouncing off one diffuse object onto
another. The sole purpose of irradiance caching is to make this computation reasonably fast. The main
idea is to perform the indirect illumination sampling only at a selected set of locations in the scene, store
the results in a cache, and reuse the cached value at other points through fast interpolation.
This book is for anyone interested in making a production-ready implementation of irradiance
caching that reliably renders artifact-free images. Since its invention 20 years ago, the irradiance caching
algorithm has been successfully used to accelerate global illumination computation in theRadiance lighting
simulation system. Its widespread use had to wait until computers became fast enough to consider global
illumination in film production rendering. Since then, its use is ubiquitous. Virtually all commercial and
open-source rendering software base the global illumination computation upon irradiance caching.
Although elegant and powerful, the algorithm in its basic form often fails to produce artifact-free
images. Unfortunately, practical information on implementing the algorithm is scarce.The main objective
of this book is to expose the irradiance caching algorithm along with all the details and tricks upon which
the success of its practical implementation is dependent. In addition, we discuss some extensions of the
basic algorithm, such as a GPU implementation for interactive global illumination computation and
temporal caching that exploits temporal coherence to suppress flickering in animations.
Our goal is to expose the material without being overly theoretical. However, the reader should
have some basic understanding of rendering concepts, ray tracing in particular. Familiarity with global
illumination is useful but not necessary to read this book.