A video game engine is the backbone of which all of the content (characters, levels, artificial intelligence, etc.) is built around. Popular game engines are updated frequently and used in a number of games before they become outdated.
The Unreal engine was first introduced in 1998 with the release of the original Unreal Tournament. Since its inception, the Unreal engine has been praised for its ability to quickly render 3D environments at a consistently high frame rate. Epic, the developers of the Unreal engine, has always encouraged user-created content with the release of official text and video documentation. Popular games that have used the Unreal engine include Bioshock 1&2, America’s Army and Tom Clancy’s Splinter Cell.
The Quake engine was first introduced in 1996 with the release of the original Quake. Quake was one of the first games to truly use a fully pre-rendered 3D environment. By only rendering what the player can see, this allowed the engine to focus more detail into what was being displayed. As of 2010, the Quake engine is the only game engine to use OpenGL, instead of the more developer-friendly DirectX. Popular games that have used the Quake engine include Quake 3, Return the Castle Wolfenstein and Half Life.
The Source engine was first introduced in 2004 with the release of Counter Strike: Source. The Source engine would eventually become the primary engine for all of Valve Software games, including Half Life 2 and Left for Dead. Source incorporates advanced rendering techniques such as “high dynamic range rendering,” which can create more realistic lighting.