What are the basics to making a Game Engine?

If you've been coding inside other games for a while, then you know what an engine gives you -- all the stuff you had when you were working with those other games...

There's 2 main parts:

* the runtime
** Usually a library of code / an SDK that will be linked into a game's exe.
** This includes all the common utilities that the game needs: rendering, physics, asset loading, timers, multi-threading building blocks, language bindings (e.g. Lua), etc...

* the tool-chain
** First you've got to figure out which DCC applications your artists/content-creators want to use.
** This includes the compilers/importers/exporters/scripts for getting models, textures, audio, etc into a format that the runtime can use.

N.B. I'm not of the opinion that it's a bad idea to make an engine. Instead, I put it in the category of "if you need to ask, then you aren't yet ready" -- you should use other engines to make games until you're able to answer the question yourself.

a good step on the way would be to make a simple game using an existing "lowish" level framework (Such as XNA, SDL, SFML, etc) without worrying about the engine abstraction, (Something like pong is a good starting point) and just go from there.

Once you're able to make reasonably big games without engines you should be able to see the path fairly clearly.

a game engine is collections of frameworks combined together.
here are the some frameworks you may use,

graphics renderers ( DirectX, OpenGL, SDL, XNA, Ogre3d, etc...)
physics ( bullet, physx, havoc, etc...)
sound (fmod, openal, etc..)
scripting (lua, python, angelscript...)

So tell me, if I am speaking to anyone who has ever made an engine of their own. How did YOU do it? How did YOU get started?
I would like to see some unique and helpful answers from you guys.

In the past, I've made a few simple games and I've made a few simple engines. Nothing commercial, just indie stuff. I hope this doesn't sound too cynical, but it's the truth. I started out on GameDev back in 04-06 with aspirations to become a game developer. Unfortunately, I got caught up in the whole "making engines rather than games" deal. Ultimately, it lead to the demise of my game development career and I moved on at the time. I'm not a person with regrets, but if I knew now what I did then, I'd have not wasted my time.

The matter of the fact is, a game engine isn't an end, it's the means. But, you have to ask yourself the means to do what?

If you want to make a game engine to understand how game engines work, there are far superior ways, such as studying and using existing successful game engines, whether they are commercial or not. I'm a strong believer in trial and error, but in terms of a time investment, getting experience and actual portfolio end product work on commonly used engines looks and feels a lot better than unpolished tech demos on an engine that you might think is great, but everyone else just shrugs at.

Don't believe me? Just take a look at some job offerings for "engine programmer/developer". I'm not going to link specific postings, because it might feel a bit like advertising, but hopefully you'll get the idea. Having your own experience is not bad, but the way you do things certainly won't always be the way the "industry" does things. If you want to compete in the "industry", you have to play their game. Even if you don't want to get into the industry, part of becoming a good programmer is finding the right tools for the job. The sooner you get over the hump of trying to do everything yourself, the sooner you can actually make your dreams come true and get stuff done.

If you want to make a game engine to make games, then you should really just make games. Here is the obligatory, Make games, not engines article. The entire read is good, but the third from last paragraph is what I want to draw the most attention to:

[background=rgb(250, 250, 250)]Most hobby developers who “finish” an “engine” that was designed and built in isolation (with the goal of having an engine, not a game, upon completion) can’t ever actually use it, and neither can anybody else. Since the project didn’t have any goals, any boundaries, or any tangible applications, it essentially attempted to solve aspect of the chosen problem space and consequently failed miserably. ....[/quote][/background]

Looking back now, as I know a lot more than I did in the past, this is exactly what happened to me, and most other people who went down this route. In a sense, this quote highlights the main problem most people have with "learning" anything. Trying to learn something as an "end" rather than as a "means" most typically leads down a hard and unsuccessful path compared to people who use it the other way around. Sure, there are exceptions, but that's why they are called exceptions.

How should you view game engines? As a manufacturing factory whose sole purpose is to speed up the production of games. You wouldn't build a factory without knowing what product you are producing, right? Unfortunately, most people do when it comes to game engines and games.

So my advice to you would be simple. Forget about the concept of "making a game engine", completely. As saejox mentioned, learn graphics rendering, physics, sound, input, scripting, multi-threaded programming, scripting, databases, tool development, etc... typical software development stuff applicable to game development. Once you learn those things, make games using them. When you have enough games made, you will see commonly recurring patterns of functionality and tools. Take all of that stuff and get it interconnected into a new project. You now have a game engine, without having made a game engine. From there, it's all about evolving the project as you continue to make more games from it.

If you have made games already, great! You are ahead of most people who want to start their own game engine. However, you still need to keep making games in order to understand the type of engine that you need to help speed up game development of similarly typed games. Making simple board games doesn't mean you are ready to make a generic game engine for a FPS, RTS, or anything like that. If you have interest in developing a broad range of games, then focusing on an engine is not a good idea, as the game development concepts can vary between game genres (e.g., action based mmorpg vs turn based rts).

This is a diagram that is posted in the book "Game Engine Architecture" which is pretty much everything a game engine needs (give or take, it's a good enough estimate in my opinion and serves as purely an example. Variety is always there)



This is pretty much everything you will need and well.. obviously it is a bit overwhelming at first glance. I've been wanting to create a game engine myself, but it is a lot of work so instead I decided to focus myself on just a "subsystem" for the time being. Creating a render engine. In my mind, once I am "done" with the render engine and I can easily/efficiently draw stuff on the screen to my liking (it's something personal, so no need to worry about others) I would be able to implement something else like Audio or Physics or whatever I want.

If you really want to make a full fledged game engine, take small steps! So in my case, I started with OpenGL, made sure I understand it (at least most of it) and try to make it as efficient as I wanted it to be. I used my teachers site which explained most of the stuff I needed to know to get started with OpenGL (http://3dgep.com/) and I would be able to continue with other stuff after that.

This might or might not be the best way, but it works for me!

Here is what I learned from my path to making something that resembles a "game engine":

1) you need a very solid "core" (math, some custom containers if needed (array,....), memory allocators, timers,...)

2) make modules totally independent of one another (module = renderer, asset loader, physics)

3) use a scripting language for the actual game

4) it will take a lot of time, so go this way only if you are interested in low-level system programming and can you live without making a game for a very long time

5) use a library for loading 3d models in the game (eg. assimp), I wrote my own c++ plugin for 3ds max but eventually I dumped that (you can later save the model loaded from assimp in your own format for performance reasons)

@Drew_Benton:

Thank you for your post.
I guess your right about the game engine being too out there for now.
I brought it up originally, because I just wanted a super simplistic engine. Nothing too fancy. Not even mesh inputs.
I basically just wanted 3D, Physics, Colored Shapes, and Player controls.

So now that we have that, where do I begin making a simple game such as this?

I have written game/rendering engines both for fun and professionally. I don't always have a use case for my engine, but when deciding on what features I'll develop, I focus on those that are needed in games like Half-Life or Deus Ex, because some day I want to be part of a team working on something like that. In the mean time, I sometimes do small indie games using my engine so I get to learn game development and not just engine development. Doing real games using your own engine is a good way to test its power.

When developing an engine, I do it in the perspective of the engine's user, and try to make everything as seamless as possible for them. First I write API calls into a tech demo, then I implement them, so it's kind of a top-down process for me.