Foundations of Precomputed Radiance Transfer

Precomputed Radiance Transfer is a joint name for a class of methods in computer graphics. The aim of these methods is fast rendering of realistic images of virtual scenes under dynamically changing but constrained lighting conditions. The techniques differ from the usual methods of real-time computer graphics in that they also support indirect lighting and non-pointlike light sources. The basic idea behind these methods is to parameterize the distribution of emitted light by a low-dimensional linear space, and to precompute response functions on the scene for each degree-of-freedom in the emission space. Rendering an image of the scene under dynamically changing illumination then proceeds by taking properly weighed sums of the precomputed response functions. This yields interactive and even real-time performance. This thesis presents a mathematical framework for methods of precomputed radiance transfer. Much of the previously published work on the subject may be seen as a special case of the presented framework. Necessary background in both mathematics and realistic image synthesis is included. äitini muistolle Acknowledgments The author thanks Timo Aila for his guidance, discussions, criticism and proofreading; professor Lauri Savioja for support, criticism, and creating a good working spirit; Jan Kautz for discussions and collaboration that led to some of the work reviewed in this thesis; Jussi Räsänen and Janne Kontkanen for discussions and proofreading; Remedy Entertainment, Ltd., for offering an inspiring working environment where the author's interest to the subject was born. Brand and product names appearing in this thesis are trademarks or registered trademarks of their respective holders.