How can I implement scripting in my game?

Question

I'm trying to write a game and implement scripting so that later on in development I won't have to recompile everything when I want to change numbers.

My problem is that I don't know how scripts should interface with the game. The scripting language I'm using is angelscript.

Right now, I have a state: the intro state, which I'm using as a test for most of the modules in my game "engine" (it's more like a loose collection of classes). It will load and draw a picture and draw text, and use scripting to update itself, and maybe switch to a dummy state afterwards to test the state manager.

While writing it, I realized that using the script to do most of the updating would require that I register most of my game engine's modules with the script, and pretty much move the bulk of the code to the scripting language. Personally, I'd rather have the C++ portion doing the majority of the work, and have the scripting language come up with the numbers to use in the formulas/drawing/whatever.

However, if I'm right, doing it that way would entail lots of different update modules for the majority of the things in the game that need to be updated, and requiring that they all be loaded in, and that the C++ code would have to run each update function individually.

Or, there's a way to achieve script and program interoperability that I'm overlooking. Either way, could someone help me figure out what the best way to get scripting implemented into my game is?

Answer 1

There's no correct answer to such a large question really. You do it the same way you would do engine/game logic separation in C++. Define an API that the script can call that allows it whatever it is you want it to do. Register functions in that API with the script, and use the API in angelscript. What that API should be depends entirely on your needs and what kind of power you want to give the scripter.

Answer 2

If you want AngelCode (or any other scripting approach of your choice) to just "come up with some numbers", hey, use it that way -- e.g., in AngelCode, compile the scripts by exposing to them a single C++ function of yours, say "void ProvideNumberFor(string reason, number value)", and the scripts will be responsible for calling that function as many times as needed to "provide the numbers", and nothing more.

Answer 3

If you're familiar with Qt4/Javscript you can always use QtScript http://qt.nokia.com/doc/4.5/qtscript.html.

Answer 4

If you look at real examples like Garry's mod or games written with UnrealScript you'll find that quite a bit of logic in modern games is implemented in the scripts. C/C++ code is best for "static" and bottleneck-prone parts of the engine, like the renderer, physics engine, low-level networking, etc. Scripts are best for content (i.e., game logic).

Aside: The best game-scripting language IMHO is Lua. It provides easy intregration with C/C++, is very well-documented, and will be familiar to users of Javascript.

I've used Lua for exactly this purpose, and it does a great job. Look at all the games programmed using Lua. Also, it's blazingly fast.

EDIT: I didn't read the question fully...sorry. This is my real answer ;)