The Ray Tracing in One Weekend series of books are now available to the public for free online. They are now released under the CC0 license. This means that they are as close to public domain as we can get. (While that also frees you from the requirement of providing attribution, it would help the overall project if you could point back to this web site as a service to other users.) These books are formatted for printing directly from your browser, where you can also (on most browsers) save...