Game engine

A game engine is a piece of software used to power and control a game. An engine is tasked with various different game-related mechanics such as graphics rendering, physics, sounds, scripting, animations, AI and resource management.

Usage in The Sims series
The Sims series utilizes a new, in-house, game engine for each base game, with expansion packs and stuff packs being built on the same engine for that specific game. For example, The Sims 2 introduced a 3D engine with visual and technical advances over its predecessor while it's sequel, The Sims 3 brought in a newer version of the engine that incorporated further visual enhancements with a fully fledged texture streaming solution to accommodate the open world.

Spin-off titles utilize a modified version of the newest available engine. An example of this is how The Sims Stories uses a modified version of the engine from The Sims 2 by decreasing the system requirements in order to make the game "laptop friendly". The Sims Medieval utilizes a modified version of the game engine from The Sims 3 with rendering enhancements.

Console titles used different engines, until The Sims 3 for console due to hardware differences. The Sims for console used a 3D rendering engine unlike its PC counterpart but limited gameplay to one floor per lot and implemented the object limiter. The Sims: Bustin' Out used an engine which featured visual enhancements on the original console engine as well as rendered load screens. The Urbz: Sims in the City up to The Sims 2: Castaway utilized a 3D engine which was incrementally updated with each game, The Sims 2 for console adding a "direct control" system allowing for third-person control over Sims as opposed to the traditional "point and click" system. The Sims 3 for console uses a "watered-down" version of the PC version's engine with the object limiter applied and the texture streaming solution omitted due to the console's RAM limitations.

Games using The Sims 2 Engine

 * The Sims 2 (plus stuff packs and expansions)
 * The Sims Life Stories
 * The Sims Pet Stories
 * The Sims Castaway Stories

Games using The Sims 3 Engine

 * The Sims 3 (plus stuff packs and expansions)
 * The Sims Medieval (plus The Sims Medieval: Pirates and Nobles)