Let me add that readers of Wilmott Magazine will recognize some of this slide material from my article
here, but also see that some of it is new. Specifically, the (legacy) Gaussian mixture model discussed in the Wilmott article and arXiv preprints has been supplemented by an -- essentially computer-instantaneous -- method using what I am calling "VIX tech" for short. These are the "two option chain methods" discussed in the slides.