Game engine

A game engine is a tool box that carries all the necessary equipment needed to rapidly build a consistent world just like the real world. For example, in real life you would expect an apple to fall to the floor if you let it go from your hand. Game makers use game engines to apply similar rules into their games which allow consistency across their game.

 Components 

 Main game program 
Game engines help game creators make rules for their games, which is also known as game logic. 

 Rendering engine 
The rendering engine creates the 3D images found in video games; most rendering engines rely on dedicated graphics tools and applications to complete these functions. To put it simply, graphics applications like Direct3D, OpenGL, or Vulkan streamline the difficult process of dealing directly with the computers graphics processing unit , the component of the computer that handles the display of images. 

 Audio engine 
The Audio Engine components of the Game Engine incorporates algorithms related to loading and modifying audio input and output. Audio engine’s allow developers to load sound onto the game by decompressing and playing audio files to simulate game sound. Possibilities are endless, an example of how complex audio engine’s can expand is the idea of a doppler effect. Doppler effects can be represented as echoes, pitch/amplitude adjustments, and oscillations.

 Physics engine 
Is responsible for emulating realistic laws of physics within the application. This consists of a set of functions for simulating physical forces and collisions. Which acts on various objects within the application during run time. 

 Artificial intelligence 
Artificial Intelligence is implemented into different parts of the main game program. For example, in player vs player video games, AI is used to create bots players can play against.

 Other websites 
 GameMiddleware.org , a reference website concerning game middleware and game engines available for commercial use
 3D Game and Graphics Engines Database, a comprehensive database of today's graphics and game engines
 Terrain in Games, an extensive overview of terrain rendering in 1997-2000 game engines