Lua Integration for Unreal Engine based on the Script Plugin by Epic. Updated to 5.0 with a few improvements

• UE5.0+

Install the python package to run this example as a gym environment

git submodule add https://github.com/Delaunay/GKLua Plugins/GKLua

1. Create a new lua file inside the your content folder
2. When the editor is going to import the script it will ask you which class this script is inheriting from.
3. When the content of the script is modified the script will be reimported by the editor

function BeginPlay()
   print("BeginPlay in lua" .. this.Get_ActorTransform())
end

function Tick(delta)
   print("Tick in lua")
end

function Destoy()
   print("End play in lua")
end

function MyCustomFunctionCallableInBlueprint()
   print("Callable")
end

• GKLuaEditor
  • "Compiles" the blueprint
    • Generate the blueprint class from a blueprint a sets up the calls
    • Code is loaded in FLuaContext::Initialize when luaL_loadstring(LuaState, TCHAR_TO_ANSI(*Code) is called
    • We can use lua_dump to retrive the compiled bytecode
    • bytecode can be loaded using lua_loadstring NOT luaL_loadstring which is currently used
  • Specialize the Blueprint Editor
• GKLuaGenerator
  • Generates lua wrappers
  • Hooks into the UHT (Unreal Header Tools) to generate the wrappers
• GKLua
  • Manage the lua VM
  • Register new libraries at runtime
  • Call Lua Functions
  • All objects that interacts with LUA get a lua_state
    • Lua can be hooked to Tick, Destoy, BeginPlay
  • You can use this in lua to access the current object being implemented by the script
  • Objects that use lua create a ScriptBlueprint which holds the lua script so lua is next to the blueprint system. Used to be able to specify a source file. seems deprecated which might mean the code is bundled in the .asset instead of being readable text.

Call a UFUNCTION

const FGeneratedWrappedFunction& InFuncDef;
UFunction* Func = InFuncDef.Func;

FStructOnScope FuncParams(Func);

// Calls the ufunction with its parameters allocated inside the struct memory
InObj->ProcessEvent((UFunction*)InFunc, FuncParams.GetStructMemory());

// return value is inside FuncParams
ReturnValue = (const FProperty* Prop, FuncParams.GetStructMemory())