Gautron P., Krivanek J. Practical Global Illumination with Irradiance Caching

Morgan and Claypool Publishers, 2009. — 148 p. — (Synthesis Lectures in Computer Graphics and Animation) — ISBN: 9781598296440Irradiance 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 the Radiance 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 mages. Unfortunately, practical information on implementing the algorithm is scarce. The main objective of this book is to show 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 show 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.Introduction to Ray Tracing and Global Illumination
Basic Radiometric Quantities
Rendering Goal: Find Radiance
Ray Tracing
Shading, Reflectance, and the BRDF
Direct and Indirect Illumination
Illumination Integral and Rendering Equation
Irradiance Caching Core
Indirect Irradiance Calculation
Irradiance Caching Algorithm
Data Structure
Irradiance Caching Summary
Practical Rendering with Irradiance Caching
Single-Pass vs. Two-Pass Image Rendering
Handling Complexity
Motion Blur
Ambient Occlusion Caching
Irradiance Caching in a Complete Global Illumination Solution
Path Grammar
Illumination Components
Recursion
Irradiance Caching on Graphics Hardware
Irradiance Splatting
Cache Miss Detection
GPU-Based Record Generation
Global Illumination Rendering
Results
Temporal Irradiance Caching
Overview of Temporal Irradiance Caching
Temporal Weighting Function
Temporal Gradients
Estimating Future Irradiance Et0+1
GPU Implementation
ResultsMathematical Foundations
(Hemi)Spheres: Care and Feeding
Continuous Random Variables in a Nutshell
Monte Carlo Integration in a Nutshell
Derivation of Gradient Formulas
Rotation Gradient Derivation
Translation Gradient Derivation
Split-Sphere Model
Annotated References
Primary Sources
Further Reading on Irradiance Caching
Background on Global Illumination