Task 17 Game engines

The game engine is the core part of games, they bring all the assets together and work them into a playable space, game engines make developing games easier and allows a company to easily port their game to different consoles.
Some engines come with a developer kit that allows the company to quickly edit their game and reduce cost, this also allows mod teams to develop their own content for the engine in question.
I would try and explain scene graphs and graphic engines but that stuff gives me a headache and will just end up as an unreadable paragraph..
Popular engines include Unreal engine, Cryengine, Doom 3, and the source engine, i've only ever used the source engine before and only made a few maps with it. i once had a go with unreal but gave up quickly.
Their are things called Middleware engines where company's develop programs to help developers build their game, one example is speedtree wich makes realistic trees really fast and saves a lot of time.
When a company starts to develop a new game they will either create their own engine or use an existing one, creating a new engine is very difficult, engines like doom 3 and quake have been constantly updated over the years and keep getting enhanced and eliminating bugs. Game engines are expensive but it could work out cheaper than coding one from scratch.
Subtractive and additive, is a term for mapping, it explains how a mapping tool works, in Additive the mapper starts with an empty environment called "the void" or "empty space", the mapper will place a room inside of this by making a hollowed out cube and sealing it, crazy stuff can happen if there is a leak in the box. Sky is created with a skybox, wich is just a normal box with a special skybox texture added to it.
Subtractive mapping uses one infinite solid space instead of a void and a mapper will hollow out the inside to create rooms, this totally gets rid of leaks but i find it an annoying way to map and prefer additive. Some people create their own void by making a giant hollow cube and adding bit inside it.