Game Technology - Game Engines

What does a game engine do?

"A game engine is the core software component of a computer video game or other interactive application with real-time graphics. It provides the underlying technologies, simplifies development, and often enables the game to run on multiple platforms such as game consoles and desktop operating systems such as Linux, Mac OS X, and Microsoft Windows. The core functionality typically provided by a game engine includes a rendering engine (“renderer”) for 2D or 3D graphics, a physics engine or collision detection (and collision response), sound, scripting, animation, artificial intelligence, networking, streaming, memory management, threading, and a scene graph. The process of game development is frequently economized by in large part reusing the same game engine to create multiple different games."
I got the above definition of game engines from wikipedia, it describes exactly what a games engine is used for.

What are the key engine technologies?

RenderWare

RenderWare is a fairly new games engine but it is used throughout the gaming industry as a rendering games it can be used for a large number of Operating Systems that are used in the gaming world. It was used on the extremely successful series of the Grand Theft Auto games before it was sold off to Electronic Arts, which then prompted Rock Star to then go on and create their own game engine RAGE.

Unreal Engine

Unreal engine was first used in 1998 for the first-person shooter game Unreal. once it had been used for this game it then went on from strength to strength. As the gaming world improved the Unreal Engine began to develop their technology with the development of Unreal Engine 2 and Unreal Engine 3. Games such as Gears Of War and various different Splinter cell games were made using this Games engine.

What is meant by subtractive and additive?

The term subtractive can be described "In a subtractive process, a block of material is carved out to produce the desired shape. Conventional prototyping processes fall into this category"
So in the gaming world I assume that this is used in the designing phase of games design.

"Any substance added in small quantities to another substance, usually to improve properties" This is the description that is used to described additive. Which in the gaming world would be when you add entities into level to create that level and make it better.