Ray Tracing in One Weekend, The Book Series, is now free.
Just update result to screen every 16ms, you can trace many pixels in that time.One weekend may be fast, but for realtime performance what we really nees is RT in under 16ms.
Basis texture compression became open source a while back, no idea how I missed to post about it here.
https://github.com/BinomialLLC/basis_universal