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

2. 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

3. 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

4. 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

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