A game engine is the key component in making a video game. The engine performs all core functions and it provides all technology, makes the development much easier and enables the game to run on multiple game platforms and operating systems. Many games companies use modified versions of older engines to make their games.
Notable Engines:
Unreal Engine 1: The original Unreal engine was debuted in 1998 and was the first game engine to integrate AI, rendering, collision detection, visibility, networking and file system into one game engine. Some functions had to be removed to maintain a high standard of performance.
Unreal Engine 2: The second Unreal engine began life with a rocky start after Unreal Tournament 2003 received mixed reviews. The engine saw the integration of the UnrealEd3 and also the core code and rendering engine were completely re-written. It also integrated the Karma physics SDK, which powered the Rag-doll physics in Unreal Tournament 2003 and Unreal Championship.
Unreal Engine 3:The third generation of the Unreal engine was developed specifically for use with DirectX 9 PCs, the Xbox 360 and the Playstation 3. Once again the render-er was re-written which supported many advanced techniques including HDRR, per-pixel lighting, and dynamic shadows, and builds upon the tools available in previous versions of the engine.

Picture taken from http://en.wikipedia.org/wiki/Unreal_engine
CryENGINE2: CryENGINE2 is a extended version of the first CryENGINE, the game engine behind FarCry. CryENGINE2 was made and developed by the German game producers Crytek and is currently being used by them to make their upcoming game Crysis. The engine was first licensed to a french architectural company called IMAGTP, they used the engine to create 3D plans of the buildings before they underwent construction. On the 17th of September 2007, Ringling College of Art & Design became the first education centre to use the engine for education purposes.
id Tech 4 Engine: The id Tech 4 engine was formerly known as the Doom 3 Engine, it was developed by the computer game company id Software and was used first in the PC game Doom 3. The engine was designed by John Carmack who created the engines used for Doom and Quake. The Doom 3 engine added several new graphical features that were not integrated in the the id Tech 3 Engine, these included bump mapping, normal mapping, and specular highlighting.

This image was taken from http://en.wikipedia.org/wiki/Id_tech_4
© Copyright 2007 David Grant WordPress Site