Scripting

Luabind is awesome.

I've spent some time with this library, and it's a really amazing C++ wrapper for Lua. Binding functions, classes, even callbacks and anonymous functions, it's a breeze.

Materials were never supposed to be hardcoded, but now the framework finally allows you to specify your own in a Lua script:

define_material(1, { name = "dirt", texture = { 1 }, hardness = 1.5 })

define_material(2, { name = "grass", texture =  { 1, 0, 1 } })

define_material(3, { name = "water", texture =  { 239 }, transparency = 0.5, viscosity = 0.2 })

...And so on. My first idea was to read this from the world database, or an XML file, but nothing is as convenient and flexible as this.

(The "texture" property is an array with 1 to 6 indices to the texture atlas. If only one value is given, all faces of the cube will use that texture. In the case of grass, texture '1' is used for the sides, '0' for the top, and '1' again for the bottom. An array with 6 values would specify different textures for every face.)

Strictly speaking, this isn't real scripting yet, just configuration. So let's take a look at events:

function launch (player)

    player:change_speed(0,0,10)

    player:shout("WHEE!")

end

on_approach(40, 40, 0, 3, 6, launch)

On_approach calls a function whenever a player gets near (40, 40, 0), within 3 blocks distance. (The coordinates are given relative to the center of the world). Any player entering this area will be launched into the air, by adding 10 m/s to their vertical speed. This event won't fire again until the player is further away than 6 blocks.

Similar triggers could be added to materials, items, and mobs. This, for example...

define_material(2, { on_touch = launch })

would be really, really annoying. But it would not overwrite anything from the first definition, it would only add a trigger.

Next thing I'll need to do is look at security. It's very important that the scripts are properly sandboxed. Also, I should study Gary's Mod, to get an idea of how to properly design such an API.


Edit: I'm jotting down some ideas here.