Spherical Harmonics lighting is a technique that achives
real-time soft global illumination by precomputing the
radiance transfer (in this case at each vertex) and saving
it as a series of spherical harmonics coefficients.
Despite producing really fantastic visuals, the technique has some serious drawbacks. The pre-processing is very intense, the scene in the video on the right took approximately 12 hours to precompute.
|Spherical Harmonics only captures low-frequency lighting, meaning no sharp shadows - this can be solved using wavelets instead. Also, the scene has to be static. No objects shadowed using Spherical Harmonics lighting can move in relation to each other, although the lightsource, which is considered to be infinitely far away, can be rotated. This makes the technique excellent for outdoor environments with dynamical weather and time of day.|