GPU Pro 6

2. Deferred Normalized Irradiance Probes 205

The irradiance computation is very similar to that of [Elias 00]: for every

single basis vector and for every cube-map texel, we project incoming radiance

to diffuse the lighting contribution. To do this efficiently, we have a multiplier

map that takes into account both Lambert’s cosine law term and the hemicube’s

shape compensation. This weight map is normalized (the sum of all texel weights

for a single basis is 1). Compensation is necessary because different cube-map

texels corresponding to different positions subtend a different solid angle on a

hemisphere. Once incoming radiance is multiplied by a bidirectiona ...