MadMarx Tutorial 9 - Part 3         Render A Texture To Itself Using A Temporary Texture

Foreword.

If you prefer tutorials that come with a framework => check the other wiki tutorial series.
If you prefer tutorials that go step by step without a framework => this page should be ok.

I assume you know C++. If not, this tutorial will probably be hard to understand !

This tutorial presents only a few elements of Ogre3D.

You can download the code and media for this tutorial at the bottom of this wiki page.
This little tutorial is an extract of a bigger project which contains more tutorials & helper classes.
This bigger project is avaible there :
https://sourceforge.net/projects/so3dtools/

Also, make sure you read these tutorials in order!

Tutorial Description

This program is mainly the same as the previous RenderToTexture tutorial,
but this time I use 'FBO' (frame buffer object).
To be able to use 'FBO' kind of render to texture, I am not allowed to
make a texture render to itself (on my graphic card at least...).
As a consequence : I create here an intermediate texture, that will receive the result
of the render to texture. So, in this program we see how to copy content from one texture
to another texture, directly on the GPU.

Conclusion : don't trust too much your graphic card's pilot.

During GL render system configuration, before root initialisation

¤					lRenderSystem->setConfigOption("RTT Preferred Mode","FBO");

After viewport creation & resource loading

Now I create a special texture. This texture allows to do what is called a
'render to texture'. Which means that you can render your scene into
it, and then use this texture as any other in a material.
In order to keep a good framerate, I set its number of mipmaps to 0.

¤	Ogre::TextureManager& lTextureManager = Ogre::TextureManager::getSingleton();
	Ogre::String lTextureName = "MyFirstRtt";
	bool lGammaCorrection = false;
	unsigned int lAntiAliasing = 0;
	unsigned int lNumMipmaps = 0;
	Ogre::TexturePtr lTextureWithRtt = lTextureManager.createManual(lTextureName, lNameOfResourceGroup, 
		Ogre::TEX_TYPE_2D, 512, 512, lNumMipmaps,
		Ogre::PF_R8G8B8, Ogre::TU_RENDERTARGET, 0, lGammaCorrection, lAntiAliasing);

I create an intermediate texture, that will receive a copy of the rtt texture.
Since I will dynamically write in this texture, I have chosen the texture usage Ogre::TU_DYNAMIC_WRITE_ONLY.
There are very detailed informations on texture usage & hardware buffers in the ogre3D manual.

¤	Ogre::String lIntermediateTextureName = "IntermediateTexture";
	Ogre::TexturePtr lIntermediateTexture = lTextureManager.createManual(lIntermediateTextureName, lNameOfResourceGroup, 
		Ogre::TEX_TYPE_2D, 512, 512, lNumMipmaps,
		Ogre::PF_R8G8B8, Ogre::TU_DYNAMIC_WRITE_ONLY, 0, lGammaCorrection, lAntiAliasing);

now I will link this texture to a camera, by creating a viewport in the texture.

¤	Ogre::RenderTexture* lRenderTarget = NULL;
	{
		Ogre::HardwarePixelBufferSharedPtr lRttBuffer = lTextureWithRtt->getBuffer();
		lRenderTarget = lRttBuffer->getRenderTarget();
		lRenderTarget->setAutoUpdated(false);

I create a camera so that it has a beautiful '1' aspect ratio.

¤		Ogre::Camera * lRttCamera = lScene->createCamera("RttCamera");
		lRttCamera->setNearClipDistance(1.5f);
		lRttCamera->setFarClipDistance(3000.0f); 
		lRttCamera->setAspectRatio(1.0f);

I attach this camera to the same node than main camera.

¤		lCameraNode->attachObject(lRttCamera);

In the texture I will draw first a Big Blue Viewport.

¤		Ogre::Viewport* lRttViewport1 = lRenderTarget->addViewport(lRttCamera, 50, 0.00f, 0.00f, 1.0f, 1.0f);
		lRttViewport1->setAutoUpdated(true);
		Ogre::ColourValue lBgColor1(1.0,0.0,0.0,1.0);
		lRttViewport1->setBackgroundColour(lBgColor1);

In the texture I will draw then a more little red Viewport.
The previous viewport with the ZOrder at 50 will be drawn first (50 < 100).

¤		Ogre::Viewport* lRttViewport2 = lRenderTarget->addViewport(lRttCamera, 100, 0.05f, 0.05f, 0.9f, 0.9f);
		lRttViewport2->setAutoUpdated(true);
		Ogre::ColourValue lBgColor2(0.0,0.0,1.0,1.0);
		lRttViewport2->setBackgroundColour(lBgColor2);
	}

This material will use the intermediate texture.

¤	Ogre::String lMaterialName = "MyRttMaterial";
	{

I get a reference on the material manager, which is a singleton.

¤		Ogre::MaterialManager& lMaterialManager = Ogre::MaterialManager::getSingleton();
		Ogre::MaterialPtr lMaterial = lMaterialManager.create(lMaterialName, lNameOfResourceGroup);
		Ogre::Technique * lTechnique = lMaterial->getTechnique(0);
		Ogre::Pass* lPass = lTechnique->getPass(0);
		Ogre::TextureUnitState* lTextureUnit = lPass->createTextureUnitState();
		lTextureUnit->setTextureName(lIntermediateTextureName);

I use no mipmap, and I just use some bilinear filtering on the result.

¤		lTextureUnit->setNumMipmaps(0);
		lTextureUnit->setTextureFiltering(Ogre::TFO_BILINEAR);

I make the texture rotate.
The material can handle 'special effects' on the texture coordinates.
Here I rotate the texture coordinates.

¤		float lRotateSpeed = 0.01f;
		lTextureUnit->setRotateAnimation(lRotateSpeed);

Entity creation

Now I will create the corresponding entity, and its scenenode.

¤	{
		Ogre::Entity* lEntity = lScene->createEntity(lNameOfTheMesh);
		lEntity->setMaterialName(lMaterialName);

Now I attach it to a scenenode, so that it becomes present in the scene.

¤		Ogre::SceneNode* lNodeWithEntity = lNodeWithEntity = lRootSceneNode->createChildSceneNode();
		lNodeWithEntity->attachObject(lEntity);

I move the SceneNode so that it is visible to the camera.

¤		lNodeWithEntity->setPosition(0.0f, 0.0f, -1.8f);
	}

Full while() loop

¤	while(!lOgreInit.mWindow->isClosed())
	{

Drawings

First I update the rendertarget, and then I make the copy of its content.
I show 2 versions of the copying.

¤		lRenderTarget->update();
		int lCopyingVersion = 1;
		if(0 == lCopyingVersion)
		{

this version resizes the texture if needed.

¤			lTextureWithRtt->copyToTexture(lIntermediateTexture);
		}else if(1 == lCopyingVersion)
		{

This version crop a part of the image to the other part.
Since I use the texture same size there is no problem.
The HardwarePixelBuffer is a pixel buffer, there is at least one per texture.
I will copy the content from the RTT-buffer to the intermediate texture-buffer.

¤			Ogre::HardwarePixelBufferSharedPtr lBufferRtt = lTextureWithRtt->getBuffer(0,0);
			Ogre::HardwarePixelBufferSharedPtr lBufferIntermediate = lIntermediateTexture->getBuffer(0,0);
			size_t left = 0;
			size_t top = 0;
			size_t right = 511;
			size_t bottom = 511;
			Ogre::Image::Box lSourceBox(left, top, right, bottom);
			Ogre::Image::Box lDestinationBox(left, top, right, bottom);

			lBufferIntermediate->blit(lBufferRtt, lSourceBox, lDestinationBox);
		}

the window update its content.
each viewport that is 'autoupdated' will be redrawn now,
in order given by its z-order.

¤		lWindow->update(false);

The drawn surface is then shown on the screen
(google "double buffering" if you want more details).
I always use vertical synchro.

¤		bool lVerticalSynchro = true;
		lWindow->swapBuffers(lVerticalSynchro);

This update some internal counters and listeners.
Each render surface (window/rtt/mrt) that is 'auto-updated' has got its 'update' function called.

¤		lRoot->renderOneFrame();

		Ogre::WindowEventUtilities::messagePump();
	}

main.cpp , main.cs

NOTE This is a quick semiautomatic convert from C++ and it works with MOGRE SDK 1.7.1 r72
Any problems you encounter while working with MOGRE should be posted to the MOGRE Forum.

//NOTE This program is similar to previous tutorial. You may use merge (e.g. WinMerge) to view difference

//TODO Dispose correctly without accessViolation error. Surround  prt with using(){} does not fix this

using System;
using System.Windows.Forms;
using Mogre;
using System.Collections.Generic;

public static class GlobalMembersMain
{
    // This program is mainly the same as the previous RenderToTexture tutorial,
    // but this time I use 'FBO' (frame buffer object).
    // To be able to use 'FBO' kind of render to texture, I am not allowed to 
    // make a texture render to itself (on my graphic card at least...).
    // As a consequence : I create here an intermediate texture, that will receive the result
    // of the render to texture. So, in this program we see how to copy content from one texture 
    // to another texture, directly on the GPU.
    //
    // Conclusion : don't trust too much your graphic card's pilot.

    // I declare a function in which I will make my whole application.
    // This is easy then to add more things later in that function.
    // The main will call this function and take care of the global try/catch.
    public static void AnOgreApplication()
    {
        // I construct my object that will allow me to initialise Ogre easily.
        OgreEasy.SimpleOgreInit lOgreInit = new OgreEasy.SimpleOgreInit();

        if (!lOgreInit.initOgre())
        {
            MessageBox.Show("Impossible to init Ogre correctly.");
            return;
        }

        //I prefer to be able to access my variables directly.
        Root lRoot = lOgreInit.mRoot;
        RenderWindow lWindow = lOgreInit.mWindow;

        // I create a scenemanager. This is like a 'Scene', in which I can put lights, 3d objects, etc...
        // The scenemanager contains an arborescent graph of 'SceneNodes'. To manage elements of the scene,
        // I will create SceneNodes in the SceneManager, and attach the elements to the scenenodes.
        // First parameter : I select a kind of SceneManager. This may have a huge impact on performance.
        // Depending on your scene, some are better than other. The default one does no optimization at all.
        // Second parameter : I give a name to the scenemanager.
        // Note : It is easy to have more than one scenemanager (If you got 2 different scenes for example).
        SceneManager lScene = lRoot.CreateSceneManager(SceneType.ST_GENERIC, "MyFirstSceneManager");

        // The 'root SceneNode' is the only scenenode at the beginning in the SceneManager.
        // The SceneNodes can be seen as 'transformation' containers <=> it contains scale/position/rotation
        // of the objects. There is only 1 root scenenode, and all other scenenode are 
        // its direct or indirect children.
        SceneNode lRootSceneNode = lScene.RootSceneNode;

        // I create a camera. It represent a 'point of view' in the scene.
        Camera lCamera = lScene.CreateCamera("MyFirstCamera");

        // I attach the camera to a new SceneNode. It will be easier then to move it in the scene.
        SceneNode lCameraNode = lRootSceneNode.CreateChildSceneNode("MyFirstCameraNode");
        lCameraNode.AttachObject(lCamera);

        // We create a viewport on a part of the window.
        // A viewport is the link between 1 camera and 1 drawing surface (here the window).
        // I can then call 'update();' on it to make it draw the Scene from the camera.
        // You can have several viewports on 1 window.
        // Check API for details on parameters.
        ushort lMainViewportZOrder = 100;
        Viewport vp = lWindow.AddViewport(lCamera, lMainViewportZOrder);

        // I want the viewport to draw the scene automatically
        // when I will call lWindow->update();
        vp.SetAutoUpdated(true);

        // I choose a color for this viewport. 
        // I prefer to have a bright color, to detect holes in geometry etc...
        vp.BackgroundColour = new ColourValue(1, 0, 1);

        // I choose the visual ratio of the camera. To make it looks real, I want it the same as the viewport.
        float ratio = vp.ActualWidth / vp.ActualHeight;
        lCamera.AspectRatio = ratio;

        // I choose the clipping far& near planes. if far/near>2000, you can get z buffer problem.
        // eg : far/near = 10000/5 = 2000 . it's ok.
        // If (far/near)>2000 then you will likely get 'z fighting' issues.
        lCamera.NearClipDistance = 1.5f;
        lCamera.FarClipDistance = 3000.0f;

        // I want my window to be active
        lWindow.IsActive = true;

        // I want to update myself the content of the window, not automatically.
        lWindow.IsAutoUpdated = false;

        // Here I choose a name for a resource group. Then I create it.
        // Often, a resourcegroup is a good way to store the data corresponding
        // to a level in a game.
        string lNameOfResourceGroup = "Mission 1 : Deliver Tom";
        {
            ResourceGroupManager lRgMgr = ResourceGroupManager.Singleton;
            lRgMgr.CreateResourceGroup(lNameOfResourceGroup);

            // The function 'initialiseResourceGroup' parses scripts if any in the locations.
            lRgMgr.InitialiseResourceGroup(lNameOfResourceGroup);

            // Files that can be loaded are loaded.
            lRgMgr.LoadResourceGroup(lNameOfResourceGroup);
        }

        // Now I create a special texture. This texture allows to do what is called a 
        // 'render to texture'. Which means that you can render your scene into 
        // it, and then use this texture as any other in a material.
        // In order to keep a good framerate, I set its number of mipmaps to 0.
        TextureManager lTextureManager = TextureManager.Singleton;
        string lTextureName = "MyFirstRtt";
        bool lGammaCorrection = false;
        uint lAntiAliasing = 0;
        int lNumMipmaps = 0;
        TexturePtr lTextureWithRtt = lTextureManager.CreateManual(lTextureName, lNameOfResourceGroup, TextureType.TEX_TYPE_2D, 512, 512, lNumMipmaps, PixelFormat.PF_R8G8B8, (int)TextureUsage.TU_RENDERTARGET, null, lGammaCorrection, lAntiAliasing);

        // I create an intermediate texture, that will receive a copy of the rtt texture.
        // Since I will dynamically write in this texture, I have chosen the texture usage TextureUsage.TU_DYNAMIC_WRITE_ONLY.
        // There are very detailed informations on texture usage & hardware buffers in the ogre3D manual.
        string lIntermediateTextureName = "IntermediateTexture";
        TexturePtr lIntermediateTexture = lTextureManager.CreateManual(lIntermediateTextureName, lNameOfResourceGroup, TextureType.TEX_TYPE_2D, 512, 512, lNumMipmaps, PixelFormat.PF_R8G8B8, (int)TextureUsage.TU_DYNAMIC_WRITE_ONLY, null, lGammaCorrection, lAntiAliasing);


        // now I will link this texture to a camera, by creating a viewport in the texture.
        RenderTexture lRenderTarget;
        {
            HardwarePixelBufferSharedPtr lRttBuffer = lTextureWithRtt.GetBuffer();
            lRenderTarget = lRttBuffer.GetRenderTarget();
            lRenderTarget.IsAutoUpdated = false;

            // I create a camera so that it has a beautiful '1' aspect ratio.
            Camera lRttCamera = lScene.CreateCamera("RttCamera");
            lRttCamera.NearClipDistance = 1.5f;
            lRttCamera.FarClipDistance = 3000.0f;
            lRttCamera.AspectRatio = 1.0f;

            // I attach this camera to the same node than main camera.
            lCameraNode.AttachObject(lRttCamera);

            // In the texture I will draw first a Big Blue Viewport.
            Viewport lRttViewport1 = lRenderTarget.AddViewport(lRttCamera, 50, 0.00f, 0.00f, 1.0f, 1.0f);
            lRttViewport1.SetAutoUpdated(true);
            lRttViewport1.BackgroundColour = new ColourValue(1.0f, 0.0f, 0.0f, 1.0f);

            // In the texture I will draw then a more little red Viewport.
            // The previous viewport with the ZOrder at 50 will be drawn first (50 < 100).
            Viewport lRttViewport2 = lRenderTarget.AddViewport(lRttCamera, 100, 0.05f, 0.05f, 0.9f, 0.9f);
            lRttViewport2.SetAutoUpdated(true);
            lRttViewport2.BackgroundColour = new ColourValue(0.0f, 0.0f, 1.0f, 1.0f);
        }

        // This material will use the intermediate texture.
        string lMaterialName = "MyRttMaterial";
        {
            // I get a reference on the material manager, which is a singleton.
            MaterialManager lMaterialManager = MaterialManager.Singleton;
            MaterialPtr lMaterial = lMaterialManager.Create(lMaterialName, lNameOfResourceGroup);
            Technique lTechnique = lMaterial.GetTechnique(0);
            Pass lPass = lTechnique.GetPass(0);
            TextureUnitState lTextureUnit = lPass.CreateTextureUnitState();
            lTextureUnit.SetTextureName(lIntermediateTextureName);
            //I use no mipmap, and I just use some bilinear filtering on the result.
            lTextureUnit.NumMipmaps = 0;
            lTextureUnit.SetTextureFiltering(TextureFilterOptions.TFO_BILINEAR);

            // I make the texture rotate.
            // The material can handle 'special effects' on the texture coordinates.
            // Here I rotate the texture coordinates.
            float lRotateSpeed = 0.01f;
            lTextureUnit.SetRotateAnimation(lRotateSpeed);

            // Uncomment the following line to see something funnier. :-D.
            // lTextureUnit.SetTransformAnimation(TextureUnitState.TextureTransformType.TT_SCALE_U,WaveformType.WFT_SINE, 0.9f, 0.5f, 0.0f, 0.2f);
        }

        // Now I will create a manualobject quad, and convert it to a mesh...
        string lNameOfTheMesh = "MyQuad";
        {
            ManualObject lManualObject = null;
            string lManualObjectName = "SomeQuad";
            lManualObject = lScene.CreateManualObject(lManualObjectName);

            // Always tell if you want to update the 3D (vertex/index) later or not.
            bool lDoIWantToUpdateItLater = false;
            lManualObject.Dynamic = lDoIWantToUpdateItLater;

            // BaseWhiteNoLighting is the name of a material that already exist inside 
            // Ogre::RenderOperation::OperationTypes.OT_TRIANGLE_LIST is a kind of primitive.
            float lSize = 0.7f;
            lManualObject.Begin("BaseWhiteNoLighting", RenderOperation.OperationTypes.OT_TRIANGLE_LIST);
            {
                float cp = 1.0f * lSize;
                float cm = -1.0f * lSize;
                float lNumberOfTiles = 1.0f;

                lManualObject.Position(cm, cp, 0.0f); // a vertex
                lManualObject.TextureCoord(0.0f, 0.0f);

                lManualObject.Position(cp, cp, 0.0f); // a vertex
                lManualObject.TextureCoord(lNumberOfTiles, 0.0f);

                lManualObject.Position(cp, cm, 0.0f); // a vertex
                lManualObject.TextureCoord(lNumberOfTiles, lNumberOfTiles);

                lManualObject.Position(cm, cm, 0.0f); // a vertex
                lManualObject.TextureCoord(0.0f, lNumberOfTiles);

                lManualObject.Triangle(2, 1, 0);
                lManualObject.Triangle(0, 3, 2);
            }
            lManualObject.End();
            lManualObject.ConvertToMesh(lNameOfTheMesh);
            lScene.DestroyManualObject(lManualObject);
        }

        // Now I will create the corresponding entity, and its scenenode.
        {
            Entity lEntity = lScene.CreateEntity(lNameOfTheMesh);
            lEntity.SetMaterialName(lMaterialName);
            // Now I attach it to a scenenode, so that it becomes present in the scene.
            SceneNode lNodeWithEntity = lRootSceneNode.CreateChildSceneNode();
            lNodeWithEntity.AttachObject(lEntity);
            // I move the SceneNode so that it is visible to the camera.
            lNodeWithEntity.Position = new Vector3(0.0f, 0.0f, -1.8f);
        }

        // cleaning of windows events managed by Ogre::WindowEventUtilities::...
        // I call it after a 'pause in window updating', in order to maintain smoothness.
        // Explanation : if you clicked 2000 times when the windows was being created, there are 
        // at least 2000 messages created by the OS to listen to. This is made to clean them.
        lRoot.ClearEventTimes();

        // I wait until the window is closed.
        // The "message pump" thing is something you will see in most GUI application.
        // It allow the binding of messages between the application and the OS.
        // These messages are most of the time : keystroke, mouse moved, ... or window closed.
        // If I don't do this, the message are never caught, and the window won't close.
        while (!lOgreInit.mWindow.IsClosed)
        {
            // Drawings

            // First I update the rendertarget, and then I make the copy of its content.
            // I show 2 versions of the copying.
            lRenderTarget.Update();
            int lCopyingVersion = 1;
            if (0 == lCopyingVersion)
            {
                // this version resizes the texture if needed.
                lTextureWithRtt.CopyToTexture(lIntermediateTexture);
            }
            else if (1 == lCopyingVersion)
            {
                // This version crop a part of the image to the other part.
                // Since I use the texture same size there is no problem.
                // The HardwarePixelBuffer is a pixel buffer, there is at least one per texture.
                // I will copy the content from the RTT-buffer to the intermediate texture-buffer.
                HardwarePixelBufferSharedPtr lBufferRtt = lTextureWithRtt.GetBuffer(0, 0);
                HardwarePixelBufferSharedPtr lBufferIntermediate = lIntermediateTexture.GetBuffer(0, 0);
                uint left = 0;
                uint top = 0;
                uint right = 511;
                uint bottom = 511;

                Box lSourceBox = new Box(left, top, right, bottom);
                Box lDestinationBox = new Box(left, top, right, bottom);

                lBufferIntermediate.Blit(lBufferRtt, lSourceBox, lDestinationBox);
            }

            // the window update its content.
            // each viewport that is 'autoupdated' will be redrawn now,
            // in order given by its z-order.
            lWindow.Update(false);

            // The drawn surface is then shown on the screen
            // (google "double buffering" if you want more details).
            // I always use vertical synchro.
            bool lVerticalSynchro = true;
            lWindow.SwapBuffers(lVerticalSynchro);

            // This update some internal counters and listeners.
            // Each render surface (window/rtt/mrt) that is 'auto-updated' has got its 'update' function called.
            lRoot.RenderOneFrame();

            WindowEventUtilities.MessagePump();
        }

        // Let's cleanup!
        {
            lWindow.RemoveAllViewports();
        }
        {
            lScene.DestroyAllCameras();
            lScene.DestroyAllManualObjects();
            lScene.DestroyAllEntities();
            lScene.DestroyAllLights();
            lRootSceneNode.RemoveAndDestroyAllChildren();
        }
        {
            RenderSystem lRenderSystem = lRoot.RenderSystem;
            lRenderSystem.DestroyRenderTarget(lTextureName);
        }
        {
            ResourceGroupManager lRgMgr = ResourceGroupManager.Singleton;
            lRgMgr.DestroyResourceGroup(lNameOfResourceGroup);
        }

        return;
    }

    public static void Main()
    {
        try
        {
            AnOgreApplication();
        }
        catch (Exception e)
        {
            OgreEasy.SimpleOgreInit.ShowOgreException();
        }
    }
}

// The classes of this tutorial are put in a namespace called OgreEasy.
// So that it can be reused without difficulty.
namespace OgreEasy
{
    /// \brief This class contains a function that help to initialise Ogre3d in one go.
    /// the code of this function is inspired by the first tutorial of OgreEasy.
    /// It was written for tutorial purpose.
    public class SimpleOgreInit
    {
        // The constructor does nothing but initialisation to NULL or empty values.
        // the constructor uses the initialisation list to have a proper state.
        public SimpleOgreInit()
        {
            mRoot = null;
            mWindow = null;
        }

        // the destructor frees memory allocated by the class.
        //public void Dispose() //TODO
        //{
        //    mRoot.Dispose();
        //    mRoot = null;
        //    mWindow = null;
        //    //mRoot.Reset(); // I was not obliged to do that...
        //}

        ///\brief  This function will create 1 ogre root and 1 window and store them in its members mRoot and mWindow.
        ///\return false if an error occurs, true otherwise.
        public bool initOgre()
        {
            bool result = false;
            // This try/catch will catch potential exception launched by ogre or by my program.
            // Ogre can launch 'Ogre::Exception' for example.
            try
            {
                // STEP 1/ First, we will need to create the Ogre::Root object.
                // It is an object that must be created to use ogre correctly, and delete once we are finished using

                // This is the name of an optionnal textual configuration file for the rendersystem.
                // I won't use it.
                string lConfigFileName = "";
                // This is the name of an optionnal textual configuration file, which lists the available plugins.
                // I won't use it.
                string lPluginsFileName = "";
                // This is the name of the log file. A log file is a file in which you can write things during the program execution.
                // Ogre use it to display general informations about the rendersystem.
                // You are not obliged to generate one, and ogre can even transmit the log data to you own class if you want.
                // Here we only ask the root to create the file.
                string lLogFileName = "Ogre.log";

                mRoot = new Root(lConfigFileName, lPluginsFileName, lLogFileName);

                // STEP 2/ Then we need to load plugins. It means that there are functions that are stored inside dynamic libraries.
                // These libraries are .dll or .so files. Most projects Ogre Project do not need all functions to be usable.
                // That way, only a subset of all function can be loaded. It also means you can create your own plugins if you want.
                // If you want to know more on the subject, you 'll need to dig into a C++ tutorial.
                // Anyway, for our use, we will need to load at least a 'RenderSystem' plugin, which means something to drive opengl or directx.
                // The basic plugins you are the most likely to use are the RenderSystems, the particle FX and the Cgprogram.
                {
                    // Here I list all the plugins I want to load.
                    // I let those I don't want to use in comments.
                    // Opengl rendersystem is supposed to work everywhere.
                    // But in reality a rendersystem may fail on your computer.
                    // It is likely do to bad/old graphic card driver/installation,
                    // or too old directx version on windows (try update).
                    // Often, when one rendersystem fail, the other at least kind-a-work.
                    // I put them in a std::vector, because then I can factorise operations and calls (do a 'for').
                    List<string> lPluginNames = new List<string>
					                                {
					                                    "RenderSystem_GL",
					                                    //"RenderSystem_Direct3D9",
					                                    "Plugin_ParticleFX",
					                                    "Plugin_CgProgramManager",
					                                    //"Plugin_PCZSceneManager",
					                                    //"Plugin_OctreeZone",
					                                    "Plugin_OctreeSceneManager",
					                                    //"Plugin_BSPSceneManager"
					                                };

                    {
                        foreach (var lPluginName in lPluginNames)
                        {
                            //TODO if (OGRE_DEBUG_MODE)  lPluginName + "_d"
                            mRoot.LoadPlugin(lPluginName);
                        }
                    }
                }

                // STEP 3/ Then, we can select from the loaded plugins the unique RenderSystem we want to use.
                {
                    // the root provide a method if you want to select
                    // the rendersystem and its options visually (lRoot->showConfigDialog()).
                    // in that case, you don't need to set the render system manually
                    Const_RenderSystemList lRenderSystemList = mRoot.GetAvailableRenderers();
                    if (lRenderSystemList.Count == 0)
                    {
                        System.Windows.Forms.MessageBox.Show("Sorry, no rendersystem was found.");
                        return result;
                    }

                    RenderSystem lRenderSystem = lRenderSystemList[0];

                    // In order to have a working RTT, I check if I can select another mode than "FBO".
                    // I suppose that the 'Copy' mode works for everyone under opengl.
                    ConfigOptionMap lConfigMap = lRenderSystem.GetConfigOptions();
                    if (lConfigMap.Find("RTT Preferred Mode") != lConfigMap.End())
                    {
                        //lRenderSystem.SetConfigOption("RTT Preferred Mode", "Copy");
                        //lRenderSystem.SetConfigOption("RTT Preferred Mode","PBuffer");
                        lRenderSystem.SetConfigOption("RTT Preferred Mode", "FBO");
                    }

                    mRoot.RenderSystem = lRenderSystem;
                }

                // STEP 4/ When the RenderSystem is selected, we can initialise the Root. The root can be initialised only when a rendersystem has been selected.
                {
                    // I can create a window automatically, but I won't do it.
                    bool lCreateAWindowAutomatically = false;
                    // name of the automatically generated window. empty for me.
                    string lWindowTitle = "";
                    // custom capabilities of the rendersystem. It's a feature for advanced use.
                    string lCustomCapacities = "";
                    mRoot.Initialise(lCreateAWindowAutomatically, lWindowTitle, lCustomCapacities);
                }

                // STEP 5/ Then we can ask to the RenderSystem to create a window.
                {
                    string lWindowTitle = "Hello Ogre World";
                    uint lSizeX = 800;
                    uint lSizeY = 600;
                    //I don't want to use fullscreen during development.
                    bool lFullscreen = false;
                    // This is just an example of parameters that we can put. Check the API for more details.
                    NameValuePairList lParams = new NameValuePairList();
                    // fullscreen antialiasing. (check wikipedia if needed).
                    lParams["FSAA"] = "0";
                    // vertical synchronisation will prevent some image-tearing, but also
                    // will provide smooth framerate in windowed mode.(check wikipedia if needed).
                    lParams["vsync"] = "true";
                    mWindow = mRoot.CreateRenderWindow(lWindowTitle, lSizeX, lSizeY, lFullscreen, lParams);
                }
                result = true;
            }
            catch (Exception e) //TODO
            {
                ShowOgreException();
                result = false;
            }

            return result;
        }

        // I put the member in public because there is no need to put them private in these tutorials.
        // It will allow very simple access to these useful members.
        ///\brief the root of ogre will be contained in this member.
        /// it will be initialised in initOgre().
        public Root mRoot = new Root();
        ///\brief the window created in the initOgre(). NULL otherwise.
        /// This is just a handle, not a real aggregation.
        /// The destruction of the Root will imply its destruction.
        public RenderWindow mWindow;

        public static void ShowOgreException()
        {
            if (OgreException.IsThrown)
                MessageBox.Show(OgreException.LastException.FullDescription, "An exception has occured!", MessageBoxButtons.OK, MessageBoxIcon.Error);
        }
    }
}