Book excerpt: Game Engine Gems brings together in a single volume dozens of new articles from leading professionals in the game development industry. Each "gem" presents a previously unpublished technique related to game engines and real-time virtual simulations. Specific topics include rendering techniques, shaders, scene organization, visibility determination, collision detection, audio, user interface, input devices, memory management, artificial intelligence, resource organization, and cross-platform considerations. A CD-ROM containing all the source codes and demos accompanies the book.