From the post: "Ray tracing was invented by Turner Whitted around 1980."
I believe that Turner probably did some great things, but somehow I don't think I believe he invented ray tracing. Ray tracing has been around for so long in physics...
Whitted published the first paper applying recursive ray tracing to the problem of rendering an image. Quibbling over this is like saying no one invented compute graphics because Renaissance artists knew how projection worked.
"Ray Tracing in One Weekend/The Next Week/The Rest of Your Life" have recently switched to DRM-free, "Pay What You Want" pricing http://in1weekend.blogspot.com/2016/01/ray-tracing-in-one-we...