History: Scripting with LuaBind in Ogre

Source of version: 5 (current)

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!!Introduction: Compiler and Developement Environment

This tutorial will teach the reader how to use ((-Lua)) and [http://www.rasterbar.com/products/luabind.html|LuaBind] in a simple Ogre application created using the Code::Blocks' development environment.

If you use VC++7 (or more) and it's dev. env., you can directly use the project files provided in [http://www.nuclex.org/articles/quick-introduction-to-luabind|this tutorial].

{DIV(class="Bloody_box2")}__Note:__ To use this tutorial you'll need reasonable experience with C++ and Ogre. If you are not ready for this tutorial then find one that's appropriate. If you're an experienced LuaBind user then you won't benefit from this simple tutorial either.{DIV}


!!Downloading and Installing the Required Libraries

Our project will be based on 3 free libraries :
# [http://www.boost.org/|Boost 1.33.1] - This library is required by LuaBind. Though some applications might require you to compile Boost the header files will be enough for this project.
# [http://luabinaries.luaforge.net/download.html|Lua 5.1.1] - You'll probably need the Sources. Read below.
# [http://sourceforge.net/project/showfiles.php?group_id=77060&package_id=77945|LuaBind 0.7] - You'll probably need the Sources too. 


!!Problem with Luabind's support of boost

As written in [http://www.nuclex.org/articles/quick-introduction-to-luabind|the "Nuclex tutorial"], "changes in the Boost library have not been reflected in LuaBind yet". So, in order to be able to compile these three libraries together, you should "set up and compile each library as well as possibly modify LuaBind". This is what we are going to do to use Luabind inside Code::Blocks.

Nevertheless, "this whole process can be somewhat troublesome", so :
# Download directly the ready-to-use pack provided on [http://www.nuclex.org/articles/quick-introduction-to-luabind|the Nuclex website] - You can download it directly by following [http://www.nuclex.org/downloads/developers/kits/luabind-binaries-and-demo|this link].

As you can see, this pack already contains compiled -Lua and Luabind libraries (both static and dynamic), but unfortunately these libraries are meant to compile in an "VC8-friendly" developement environment, that means that for example you'd need the Windows SDK to add them to your project. It would be one more (heavy) SDK to download, this is why it's easier to recompile these libraries in a "pure Code::blocks" way (Code::Blocks with the MinGW compiler provide the minimum required files to compile Win32 applications without downloading the whole Windows SDK).

This is exactly what we are going to do. Read below.


!!Prerequisite : Creating an Ogre Project

# Run Code::Blocks, then use the wizard to create a new "Ogre3D project" that we will name ''myOgreProject''. Run it.

If it doesn't run fine, then it means that you have a problem with your installation of Code::Blocks/the Ogre3D SDK/the DirectX SDK/whatever else. In this case, read the ((CodeBlocks MingW STLPort|installation instructions)) again.


!!Add -Lua and Luabind projects to your Code::Blocks Solution

The goal of this step is to take advantage of Lua/Luabind/Boost's modified sources mentioned previously and to insert them in our solution as Code::Blocks projects instead of VC++8 projects.

Follow these instructions : 
# Unpack the "Nuclex Pack" archive somewhere. It should be named ''luabind-binariesAndDemo'' if you kept the original name. We'll come back to this directory later.
# Unpack the ''library-sources.zip'' archive contained in the previous one. In the newly created folder, you should find a Visual Studio solution (.sln) and the three "modified" folders in which we find a so great interest : boost_1_33_1_lite, [http://lua-5.1.1|lua-5.1.1] and luabind.
# Copy the ''library-sources'' folder to your ''myOgreProject'' folder.

__Creating the -Lua project :__
# In ''myOgreProject\library-sources\lua-5.1.1\Build'', create a ''CodeBlocks'' folder, just next to the ''MSVC8'' folder. The location of our Code::Blocks project is not important, but it's nicer to keep the original directories structure ;-)
# Inside Code::blocks, Create a new project. In the list, choose the "Static library" project type. Name it ''lua-5.1.1''. Place it at the location ''myOgreProject\library-sources\lua-5.1.1\Build\CodeBlocks''. This new project should appear in your solution, under your ''myOgreProject'' project.
# Right-click on the ''lua-5.1.1'' project and select "Add files...". Select all ".c" and ".h" files from the ''myOgreProject\library-sources\lua-5.1.1\src'' folder.
# Set the ''lua-5.1.1'' project as the active project and compile it. It should compile well.

__Creating the Luabind project :__
# (same as above) In ''myOgreProject\library-sources\luabind\Build'', create a ''CodeBlocks'' folder, just next to the ''MSVC8'' folder.
# (same as above) Inside Code::blocks, Create a new project. In the list, choose the "Static library" project type. Name it ''luabind''. Place it at the location ''myOgreProject\library-sources\bind\Build\CodeBlocks''. This new project should appear in your solution, under your ''lua-5.1.1'' project.
# (same as above) Right-click on the ''luabind'' project and select "Add files...". Select all ".cpp" files from the ''myOgreProject\library-sources\luabind\src'' folder.
# Right-click on the ''luabind'' project and select "Build Options". In the left pane, click on "luabind", so that your actions have effect on both "Release" and "Debug" configurations. Click on "Directories" pane, then on "Compiler" subpane. Click on "add" three times, to add these 3 folders :
{CODE(wrap="1")}     * luabind
     * lua-5.1.1\src
     * boost_1_33_1_lite{CODE}

Everytime, keep them as relative paths. Now, your ''luabind'' project know where to find the headers of these 3 projects. Click OK.
# Right-click on the ''luabind'' project and select "Properties...". Then click on "Project's dependencies". Select "luabind" and check "depends on lua-5.1.1". Click OK. Note : ''luabind'' doesn't really depend on ''lua'' but later the order of compilation will be important when we'll use both projects in our Ogre3D project.
# Set the ''luabind'' project as the active project and compile it. It should compile well.

If both compilations went well, you should now have two files :
{CODE(wrap="1")}     * ''myOgreProject\library-sources\bind\Build\CodeBlocks\lua-5.1.1\obj\Debug\liblua-5.1.1.a''
     * ''myOgreProject\library-sources\bind\Build\CodeBlocks\luabind\obj\Debug\libluabind.a''{CODE}
(replace ''Debug'' by ''Release'' if you compiled as Release)

Note that these libraries are named the Linux way. they are named "libxxxxxx.a" instead of "xxxxxx.lib", but they work anyway!

__Reference lua and luabind static libraries in your Ogre3D project :__
# Right-click on your ''myOgreProject'' and select "Build Options".
# In the left pane, select "Debug" (resp. "Release") and in the "link libraries" pane add the two files we mentioned above :
{CODE(wrap="1")}     * ''myOgreProject\library-sources\bind\Build\CodeBlocks\lua-5.1.1\obj\Debug'''(resp. Release)'''\liblua-5.1.1.a''
     * ''myOgreProject\library-sources\bind\Build\CodeBlocks\luabind\obj\Debug'''(resp. Release)'''\libluabind.a''{CODE}
Both libraries are now part of the project, but we don't use them yet, so in effect nothing has changed.
# Right-click on the ''myOgreProject'' project and select "Properties...". Then click on "Project's dependencies". Select "myOgreProject" and check "depends on luabind". Now, each project will be compiled in the right order for you to always have up-to-date libraries.

__Enable Luabind in your project :__
# In your ''myOgrePrject'' folder, create an ''Include'' folder.
# Now it's time to go back to your ''luabind-binariesAndDemo'' folder. Copy the contents of it's ''Include'' folder into your ''myOgreProject\Include'' folder. You now have the include files from lua, luabind and boost available in your project and they will travel with it if you move it. ;-)
# You may delete ''luabind-binariesAndDemo'', you don't need it anymore.
# Inside Code::Blocks, right-click on the ''myOgreProject'' project and select "Build Options". In the left pane, click on "myOgreProject", so that your actions have effect on both "Release" and "Debug" configurations. Click on "Directories" pane, then on "Compiler" subpane. Click on "add" and add the ''myOgreProject\Include'' directory we created above, so that we didn't copy the include files for nothing ;-) Now, the compiler knows where to find them.
# Add this code at the top of your main.cpp file :
{CODE(wrap="1", colors="c++")} // Include the lua headers (the extern "C" is a requirement because we're
 // using C++ and lua has been compiled as C code)
 extern "C" {
   #include "lua/lua.h"
   #include "lua/lauxlib.h"
 }
 
 // This is the only header we need to include for LuaBind to work
 #include "luabind/luabind.hpp"{CODE}

# In it's current state, compiling and running your program will run the ''Lua'' console, which is a bit intrusive! This happens if you are using the ''MigW'' compiler and linking to static libraries as described above, your workspace now contains multiple ''main()'' functions. Either explicitly comment out the ''WinMain()'' which gets generated by code::blocks's ogre3D wizard, or if you need to use ''windows.h'', you can modify the code in ''main.cpp'' to look as follows (although I would also, alternatively, suggest you include windows.h in a common header file).:
{CODE(wrap="1", colors="c++")} // ----------------------------------------------------------------------------
 // Ogre Generated Main function, just boots the application object
 // ----------------------------------------------------------------------------
 #if OGRE_PLATFORM == OGRE_PLATFORM_WIN32
 #define WIN32_LEAN_AND_MEAN
 #include "windows.h"
 INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR strCmdLine, INT );
 
 int main(int argc, char **argv)
 {
         return WinMain(GetModuleHandle(0),0,GetCommandLine(),0);
 }
 
 INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR strCmdLine, INT )
 #else
 int main(int argc, char **argv)
 #endif{CODE}

Note: If you just want to run your application as a console-style application, comment out the code related to ''OGRE_PLATFORM_WIN32'' within your ''main.cpp'' file generated by code::blocks's ogre3D wizard.

Our project is now fully ready to welcome some luabind code!

__Add a link to Lua's State:__
# modify the following code block (created by default by code::blocks's ogre3D wizard) to add the luabind code :
{CODE(wrap="1", colors="c++")}   try
    {
        lua_State *pMyLuaState = lua_open(); //Add this
        app.go();
        lua_close(pMyLuaState); //Add this too
    }{CODE}

You can find explanations concerning this code in the next paragraph.

# Set the ''myOgreProject'' project as the active project and compile it. If it compiles well, then you're ready to code with lua and luabind !

!!How -Lua works
-Lua is used primarily through an object called a __lua_State__. This is Lua's virtual machine. It's somewhat like a seperate mini-program running within your application.

To use -Lua we need a pointer to our ''lua_State''. It's ''pMyLuaState''.
{CODE(wrap="1", colors="c++")}pMyLuaState= lua_open(); // initialize mLuaState for Lua{CODE}

And now -Lua is initialized and ready to be given a .lua file to work with.

Shutting down -Lua is just as easy. Add this code to your deconstructor.
{CODE(wrap="1", colors="c++")} if( pMyLuaState)
 {
     lua_close(pMyLuaState);
     pMyLuaState= 0;
 }{CODE} 


!!Further coding in LUA

You should read these turorials: 
# [http://www.rasterbar.com/products/luabind/docs.html] 
# [http://www.nuclex.org/articles/quick-introduction-to-luabind]

!! See also

* ((-Lua|Lua)) - Ogre wiki
* [http://www.lua.org|lua.org] — official site
* [http://en.wikipedia.org/wiki/Lua_%28programming_language%29|Lua] at Wikipedia
* [http://en.wikibooks.org/wiki/Lua_Functional_Programming|Lua Functional Programming] — Wiki Books
* [http://www.onlamp.com/pub/a/onlamp/2006/02/16/introducing-lua.html|Introducing Lua] — ONLamp.com.
* [http://www.ibm.com/developerworks/linux/library/l-lua.html|Embeddable scripting with Lua] — IBM developerWorks
* [http://lugre.schattenkind.net|Lugre] - A crossplatform gamedev framework/library with Lua-bindings for Ogre3d


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Alias: (alias(Scripting_with_LuaBind_in_Ogre))
History: Scripting with LuaBind in Ogre

Source of version: 5 (current)

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