Wrote my first ray tracer at 15, wrote a demoscene realtime ray tracing tutorial at 17, am now 37 and have been writing ray tracers professionally for over 10 years. Have also had the pleasure of teaching ray tracing to sort of everyone who'll listen (some went on to do PhDs, one became a lead gfx programmer on GTA 5, the 3rd most recent was 12 years old, ...), it's like a nerdy Jehovah's Witness / Monte Carlo Methodist Church.

It's been pretty great; realtime rendering gets all the hype, but offline rendering is where realtime is headed and this is a super exciting time with all this parallel computation around.