Glass spheres in a ray tracer

In an earlier post I was wondering whether the image projected on the floor was a bug.    I got a dielectric sphere from Amazon and just set up a ugly ducking Cornell Box made out of foam-core.   Apparently, spheres are more effective lenses than I realized and it is probably not a bug.

The projected image of the ipad is more visible on the floor than I expected.

I'll be doing a more full spectral validation of my renderer this week.    It's fun in an artsy crafty first grade maker movement kind of way!