What just happened? It's in Nvidia's best interests to get as many developers aboard the ray tracing bandwagon as possible, and as quickly as possible. Publishing a wide-ranging book on the topic - and giving it away for free - is certainly one way to help accomplish that goal.
Nvidia is going all in on ray tracing. The GPU maker recently announced plans to publish a book on the subject in the coming months that'll serve to educate developers at all levels on key concepts surrounding the technology.
Nvidia has commissioned more than 60 experts in the field of ray tracing to contribute to the project. The technology company says the book isn't meant as a survey of the field of ray tracing - there are already plenty of resources on that subject. Instead, it covers techniques that aren't often discussed in general texts but are important in reaching high-quality results. There are also tutorials on newer technologies and guides that highlight best practices for solving specific issues.
A hardback version of Ray Tracing Gems will be available mid-March at the Game Developers Conference (March 18 through March 22) and at Nvidia's own GPU Technology Conference (March 18 through March 21).
Optionally, you can download the book as a series of seven PDFs as they become available, free of charge. Part I is already online and can be accessed over on Nvidia's website. Note that you'll need to be a member of Nvidia's Developer Program to gain access.
A new section of the book is scheduled to be released every few days through the end of February.