KIPA Game Engine Seminars Day 9 Jonathan Blow Ajou University December 5, 2002

Dealing with Global Illumination The BRDF technique discussed yesterday involves only point light sources Most realtime techniques right now don’t involve self-occlusion Complex scenes involve secondary reflections, self-occlusion, and all that stuff Graphics are “good enough” now that it won’t help to make them better in terms of resolution, color depth, and triangle count, unless we start taking care of global illumination Show the teapot again

Chas Boyd’s slides Chas did a lecture at GDC 2002 about this His slides are pretty good, so I’ll use them to talk about the issues

The idea behind spherical harmonics Suppose we want to approximate a 1D function on a linear domain (like time) We can Fourier transform the function If we assume the function is mostly low-frequency, we can throw away most of the Fourier coefficients We can reconstruct a function approximation by adding together the low-frequency terms

Reflectance functions are defined on S2 (nonlinear domain) The spherical harmonics are orthogonal basis functions on S2