Ok, this is more of a terminology question as opposed to a technical question, but here is it anyway: What exactly is the difference between a game engine and the game itself? I keep hearing people say "Oh, that book is only good if you''re trying to design a game engine, not the actual game." Say what?! Also, this may tie in with the answer, what would source code be considered? For example, the source code for Descent? The engine?

Source code is the actual text form of the uncompiled program or engine. An engine can be a lot of things, anything from a complete game that can simply have the graphics changed to be a unique game, or the base tools needed to build a game such as graphics importers/compressors, sound controllers, 3D equations, ect.

My understanding has been that an engine is a portion of code that performs a function... so the code that reads your map data and translates that into a series of bitmaps on your screen is your rendering engine. By the same thinking, your save and load functions could be your file handling engine. =) I guess it depends on how you put it together too.

From one of my old webpages:


What is a Game Engine

A game engine is a platform to make games on. Many people have the false idea that a game engine is a game. This is not true. A game engine does general things such as render graphics, render characters, control animations, play sounds & music, control physics, control AI and render world geometry. None of these functions mention any specific game elements like guns and vehicles. This is because a game engine doesn''t know what a gun or a vehicle is. This is a good thing because we don''t want the engine to know what these things are. That way it is an open slate for virtually any kind of game.



What is Gamecode

It is the job of the game programmer to create the gamecode that sits on top of the engine. This is done by writing a program, typically in C/C++, that defines the game elements and gameplay. The game program calls functions of the engine to perform various services such as rendering a world or playing a character animation. Most game engines have API''s for accessing engine services in exactly the same way that the Windows has an API for writing Windows-based programs.