Supplement for real-time soft shadows in dynamic scenes using spherical harmonic exponentiation

Given the blocker spheres at a vertex, we accumulate the blocker visibility log vectors f[i] to yield the total log visibility vector f, and then perform SH exponentiation to transform the log vector back to a product space visibility vector, g = exp*(f). The result is then used in the (H(N)*L)·g shading computation. To save an SH product, we precompute LH(N)=H(N)*L, stored as a cube map, and do a cube map lookup using the normal vector N as the index.