How did they do it?

Question

Something just crossed my mind, How does a developer make a new game using the engine of another game, for example, how did Infinity Ward make Call Of Duty from the Quake 3 Engine(id Tech 3), which has mostly code for Quake 3: Arena.

I mean, was it as easy as replacing all the Quake 3 Arena specific code with code for Call Of Duty, because I'm confident they did'nt simply have the engine and all they had to do was write the code for their game, I'm certain that game engines back then were not THAT easy.

Answer 1

the game engine is used to simplify the job of game developers. it is like a framework that offers features to make a game without making everything from scratch .
it's kind of independent from the game itself, meaning that what you choose to use the engine for, is up to you .
it's like what happens with car makers, some manufacturers make the engine and it is used in other brands.
i.e Volkswagen engine is used in many cars but they are not all the same in terms of design, quality....

Answer 2

the engine is just the framework handling the basic, low level computing tasks related to reading input, playing sound, drawing/rendering things and some basic logic such as collision detection, event handlers etc.
the game is built on top of this technology, and this has always been the case.
don't confuse game development with game modding by the way, it's not quite the same.

Answer 3

IDGam3r Quake 3 Arena has already been open source since 2005, aka for ~15 years now. 😅

Answer 4

Id tech engines separate code in to the engine and game code. Game code contains logic for all entities that can be contained within maps, like weapons, interactable objects in the map, AI, vehicles, etc. Call of Duty originally was made by just removing all Quake related entities and adding Call of Duty ones. To make a full separate game you'd need to produce your own textures, models and pack them in to maps, modify the HUD and the menu and change the name of the game to "Call of Duty". You can try doing all of that yourself, as the source code to Quake 3 Arena (with the id tech 3 engine) is available on github: https://github.com/id-Software/Quake-III-Arena

Answer 5

So, If ID Releases the source code for Quake 3 Arena, which uses ID Tech 3(ID's most comercially sucessful engine), does that mean all one has to do is erase the Quake 3 specific code and add the code for their game.

Answer 6

I know that, What I was meaning was The ID Tech engines don’t release as a engine on its own, so when Infinity Ward used ID Tech 3(Quake 3's Engine, Which they would have to download the source code of to be able to use the engine itself), would they have to replace all the Quake 3 specific code with code for their game??

Answer 7

unless they got access to a more barebone distribution of the engine, yes. delete the assets and adapt/extend the code.

Answer 8

ah, I bet that process can take a while