| Tutorial 12. Terrain Rendering
This tutorial will briefly show how to use the terrain renderer of Irrlicht. It will also show the terrain renderer triangle selector to be able to do collision detection with terrain. The program which is described here will look like this: Note that the terrain renderer in Irrlicht is based the terrain renderer by Soconne and the GeoMipMapSceneNode developed by Spinz, lots of thanks go to them.

Lets start!
In the beginning there is nothing special. We include the needed header files and create an event listener to listen if the user presses the 'W' key so we can switch to wireframe mode and if he presses 'D' we toggle to material between solid and detail mapped.
    #include <irrlicht.h>
    #include <iostream>
    using namespace irr;

    #pragma comment(lib, "Irrlicht.lib")

    class MyEventReceiver : public IEventReceiver
    {
    public:
    	MyEventReceiver(scene::ISceneNode* terrain)
    	{
    		// store pointer to terrain so we can change its drawing mode
    		Terrain = terrain;
    	}

    	bool OnEvent(const SEvent& event)
    	{
    		// check if user presses the key 'W' or 'D'
    		if (event.EventType == irr::EET_KEY_INPUT_EVENT && !event.KeyInput.PressedDown)
    		{
    			switch (event.KeyInput.Key)
    			{
    			case irr::KEY_KEY_W: // switch wire frame mode
    				Terrain->setMaterialFlag(video::EMF_WIREFRAME, !Terrain->getMaterial(0).Wireframe);
    				return true;
    			case irr::KEY_KEY_D: // toggle detail map
    				Terrain->setMaterialType(
    					Terrain->getMaterial(0).MaterialType == video::EMT_SOLID ?
    					video::EMT_DETAIL_MAP : video::EMT_SOLID);
    				return true;
    			}
    		}
    		return false;
    	}

    private:
    	scene::ISceneNode* Terrain;
    };
The start of the main function starts like in most other example. We ask the user for the desired renderer and start it up.
    int main()
    {
    	// let user select driver type

    	video::E_DRIVER_TYPE driverType = video::EDT_DIRECT3D9;

    	printf("Please select the driver you want for this example:\n"\
    		" (a) Direct3D 9.0c\n (b) Direct3D 8.1\n (c) OpenGL 1.5\n"\
    		" (d) Software Renderer\n (e) Apfelbaum Software Renderer\n"\
    		" (f) NullDevice\n (otherKey) exit\n\n");

    	char i;
    	std::cin >> i;

    	switch(i)
    	{
    		case 'a': driverType = video::EDT_DIRECT3D9;break;
    		case 'b': driverType = video::EDT_DIRECT3D8;break;
    		case 'c': driverType = video::EDT_OPENGL;   break;
    		case 'd': driverType = video::EDT_SOFTWARE; break;
    		case 'e': driverType = video::EDT_BURNINGSVIDEO;break;
    		case 'f': driverType = video::EDT_NULL;     break;
    		default: return 1;
    	}

    	// create device
    	IrrlichtDevice* device = createDevice(driverType, core::dimension2d<s32>(640, 480));

    	if (device == 0)
    		return 1; // could not create selected driver.
First, we add standard stuff to the scene: A nice irrlicht engine logo, a small help text, a user controlled camera, and we disable the mouse cursor.
    video::IVideoDriver* driver = device->getVideoDriver();
    scene::ISceneManager* smgr = device->getSceneManager();
    gui::IGUIEnvironment* env = device->getGUIEnvironment();

    driver->setTextureCreationFlag(video::ETCF_ALWAYS_32_BIT, true);

    // add irrlicht logo
    env->addImage(driver->getTexture("../../media/irrlichtlogoalpha.tga"),
        core::position2d<s32>(10,10));

    // add some help text
    gui::IGUIStaticText* text = env->addStaticText(
    	L"Press 'W' to change wireframe mode\nPress 'D' to toggle detail map",
    	core::rect<s32>(10,453,200,475), true, true, 0, -1, true);

    // add camera
    scene::ICameraSceneNode* camera =
        smgr->addCameraSceneNodeFPS(0,100.0f,1200.0f);
    camera->setPosition(core::vector3df(1900*2,255*2,3700*2));
    camera->setTarget(core::vector3df(2397*2,343*2,2700*2));
    camera->setFarValue(12000.0f);

    // disable mouse cursor
    device->getCursorControl()->setVisible(false);
Here comes the terrain renderer scene node: We add it just like any other scene node to the scene using ISceneManager::addTerrainSceneNode(). The only parameter we use is a file name to the heightmap we use. A heightmap is simply a gray scale texture. The terrain renderer loads it and creates the 3D terrain from it. To make the terrain look more big, we change the scale factor of it to (40, 4.4, 40). Because we don't have any dynamic lights in the scene, we switch off the lighting, and we set the file terrain-texture.jpg as texture for the terrain and detailmap3.jpg as second texture, called detail map. At last, we set the scale values for the texture: The first texture will be repeated only one time over the whole terrain, and the second one (detail map) 20 times.
    // add terrain scene node
    scene::ITerrainSceneNode* terrain = smgr->addTerrainSceneNode(
          "../../media/terrain-heightmap.bmp");

    terrain->setScale(core::vector3df(40, 4.4f, 40));
    terrain->setMaterialFlag(video::EMF_LIGHTING, false);

    terrain->setMaterialTexture(0, driver->getTexture("../../media/terrain-texture.jpg"));
    terrain->setMaterialTexture(1, driver->getTexture("../../media/detailmap3.jpg"));

    terrain->setMaterialType(video::EMT_DETAIL_MAP);
    terrain->scaleTexture(1.0f, 20.0f);
To be able to do collision with the terrain, we create a triangle selector. If you want to know what triangle selectors do, just take a look into the collision tutorial. The terrain triangle selector works together with the terrain. To demonstrate this, we create a collision response animator and attach it to the camera, so that the camera will not be able to fly through the terrain.
    // create triangle selector for the terrain
    scene::ITriangleSelector* selector =
        smgr->createTerrainTriangleSelector(terrain, 0);
    terrain->setTriangleSelector(selector);

    // create collision response animator and attach it to the camera
    scene::ISceneNodeAnimator* anim = smgr->createCollisionResponseAnimator(
    	selector, camera, core::vector3df(60,100,60),
    	core::vector3df(0,0,0),
    	core::vector3df(0,50,0));
    selector->drop();
    camera->addAnimator(anim);
    anim->drop();
To make the user be able to switch between normal and wireframe mode, we create an instance of the event reciever from above and let Irrlicht know about it. In addition, we add the skybox which we already used in lots of Irrlicht examples.
    // create event receiver
    MyEventReceiver receiver(terrain);
    device->setEventReceiver(&receiver);

    // create skybox
    driver->setTextureCreationFlag(video::ETCF_CREATE_MIP_MAPS, false);

    smgr->addSkyBoxSceneNode(
    	driver->getTexture("../../media/irrlicht2_up.jpg"),
    	driver->getTexture("../../media/irrlicht2_dn.jpg"),
    	driver->getTexture("../../media/irrlicht2_lf.jpg"),
    	driver->getTexture("../../media/irrlicht2_rt.jpg"),
    	driver->getTexture("../../media/irrlicht2_ft.jpg"),
    	driver->getTexture("../../media/irrlicht2_bk.jpg"));

    driver->setTextureCreationFlag(video::ETCF_CREATE_MIP_MAPS, true);
That's it, draw everything. Now you know how to use terrain in Irrlicht.
    	int lastFPS = -1;

    	while(device->run())
    	if (device->isWindowActive())
    	{
    		driver->beginScene(true, true, 0 );

    		smgr->drawAll();
    		env->drawAll();

    		driver->endScene();

    		// display frames per second in window title
    		int fps = driver->getFPS();

    		if (lastFPS != fps)
    		{
    			core::stringw str = L"Terrain Renderer - Irrlicht Engine [";
    			str += driver->getName();
    			str += "] FPS:";
    			str += fps;
    			device->setWindowCaption(str.c_str());
    			lastFPS = fps;
    		}
    	}

    	device->drop();

    	return 0;
    }