Transmission rays generated

Bright ring around edge of sphere not in evidence, though total
internal reflection seems to be occurring on the lower edges.

May need to use different epsilon point in the case of total
internal reflection.
Shadow rays take transmissiveness into account

Lights which would attempt to illuminate a surface point from below
are culled before passing to the illumination model.

Specular highlights can be seen on the back of the sphere. I'm
not sure if that's desirable.
Retrieved non-extra dumb shadow image from earlier