The Red Book is worth paying for. It will save you hundreds of hours of head-scratching over why your texture is black or why your triangle won't render. Spend the $30. Your future rendering engine will thank you.
For decades, one book has sat on the desks of graphics programmers, from novices at game development to engineers at aerospace simulation firms: The OpenGL Programming Guide . Affectionately known as the "Red Book" for its iconic cover, this series has been the definitive tutorial and reference for the industry-standard 2D and 3D graphics API.
While you cannot legally find a free PDF of the 9th edition, you have excellent alternatives: borrow it digitally via O'Reilly, buy a cheap used print copy, or invest in the 10th edition e-book. Avoid sketchy PDF websites—they are often outdated scans missing code listings or, worse, vectors for viruses.
