Scripting with Lua

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Original post by rasher_b2 The problem is that each instance of a trigger needs a separate onHit function. So I thought maybe I could create a table that maps trigger ids to their onHit function. Now each trigger can have a separate function.

OnHitFunctions[MyTrigger](MyTrigger, params)

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Original post by theOcelot Makes sense to me. Another thing you could do is a table that maps the trigger itself, whether its a table or userdata, to its onHit function. OnHitFunctions[MyTrigger](MyTrigger, params)

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Original post by rasher_b2 Quote: Original post by theOcelot Makes sense to me. Another thing you could do is a table that maps the trigger itself, whether its a table or userdata, to its onHit function. OnHitFunctions[MyTrigger](MyTrigger, params) Thanks for the reply. That makes sense too. Actually, the more I think about it, the more it seems I should move my game logic to Lua and have the C++ part of my game provide services such as rendering and physics.

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Another thing is: if I were to create a game object with all its logic implemented in Lua...how is this generally done? Could each object, in C++, have a tick function that calls some Lua function? Or is this generally not how that problem is approached.

class Entity{  void update() {}  void onHit() {  ... do some stuff..}  void onOtherTrigger() { ... do other stuff..}}

object_pool = {}registerNewObject = function( _cplusplus_reference)  object_pool[reference] = {}  _lua_object.ref = _cplusplus_referenceendgetObject = function( _cplusplus_reference)  return object_pool[_cplusplus_reference]endgetReference = function( _object)  return _object.refend

class Entity{  void update() { callLuaObjectFunc(this,"update");}  void onHit() { callLuaObjectFunc(this, "on_hit");}  void onCollision() { callLuaObjectFunc(this,"collision"}}

callFunc = function( _cplusplus_ref, _function_name)  local obj = getObject( _cplusplus_ref)  -- check if method is present  if obj[_function_name]~=nil then    -- call method    obj[_function_name](obj)  endend

react_to_hit = function( _obj)  .. react to hitendlook_for_enemy = function( _obj)  .. scan surrounding for enemiesendinitMonster = function(_cplusplus_ref)  local obj = getObject( _cplusplus_ref)  obj.on_hit = react_to_hit  obj.update = look_for_enemyend

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Original post by Ashaman73 Well, this is not an issue with including a script language into your game. Using trigger, ticks , updates etc. could be all solved completly in c++ or in lua. The question is, where to make the cut :-)

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Original post by rasher_b2 Quote: Original post by Ashaman73 Well, this is not an issue with including a script language into your game. Using trigger, ticks , updates etc. could be all solved completly in c++ or in lua. The question is, where to make the cut :-) Yep, could be done in either but just need to decide where to separate things. I did have an Entity with tick, etc. functions in C++. However, after some thinking and prototyping, I have decided to split things a bit lower down so entities only exist on the Lua side of things. This means I just handle things like rendering, physics, etc. on the C++ side. What I'm doing now is creating a Lua state when my game starts. I keep this state around until the game exits. Lua can use the C++ API to create game states (a game state is something like the menu, game world, pause menu). As the game loop runs, it calls a tick function in Lua that runs the active state's logic. Input events are also propagated to the Lua code. I'm not sure how much sense that made. I've left out many details but it's been working well for me so far. I'll elaborate if anyone wants to continue the discussion.

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Original post by Ashaman73 Quote: Another thing is: if I were to create a game object with all its logic implemented in Lua...how is this generally done? Could each object, in C++, have a tick function that calls some Lua function? Or is this generally not how that problem is approached. Well, this is not an issue with including a script language into your game. Using trigger, ticks , updates etc. could be all solved completly in c++ or in lua. The question is, where to make the cut :-) I don't know your game (c++) structure sofar, but it seems that you already have some kind of gamelogic in c++, something like this: *** Source Snippet Removed *** My way to handle this in my game is to map each C++ entity to an lua object. In lua this could look like *** Source Snippet Removed *** Whenever you create a c++ entity, call the registerNewObject function. Next you should use your c++ entity to interface the lua functions: *** Source Snippet Removed *** The callLuaObjectFunc will call something like this in your lua scripts: *** Source Snippet Removed *** Eventually you can add individual functions for each object to handle object dependent behaviour by simply assigning functions to each lua object: *** Source Snippet Removed ***

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Original post by theOcelot Sounds cool to me. So Lua functions request graphical and physical objects from the C++ engine?

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Original post by AverageJoeSSU What im working on now is constructing a level in lua.

entity{ class = "Player", args = { pos = vector2(10, 10) --[[ some more args here ]]} }