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.

Note that the Terrain Renderer in Irrlicht is based on Spintz' GeoMipMapSceneNode, lots of thanks go to him. DeusXL provided a new elegant simple solution for building larger area on small heightmaps -> terrain smoothing.

In the beginning there is nothing special. We include the needed header files and create an event listener to listen if the user presses certain keys.

#include <irrlicht.h>
#include "driverChoice.h"
#include "exampleHelper.h"

using namespace irr;

#ifdef _MSC_VER
#pragma comment(lib, "Irrlicht.lib")
#endif


class MyEventReceiver : public IEventReceiver
{
public:

    MyEventReceiver(scene::ISceneNode* terrain, scene::ISceneNode* skybox, scene::ISceneNode* skydome) :
        Terrain(terrain), Skybox(skybox), Skydome(skydome), showBox(true), showDebug(false)
    {
        Skybox->setVisible(showBox);
        Skydome->setVisible(!showBox);
    }

    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);
                Terrain->setMaterialFlag(video::EMF_POINTCLOUD, false);
                return true;
            case irr::KEY_KEY_P: // switch point cloud mode
                Terrain->setMaterialFlag(video::EMF_POINTCLOUD,
                        !Terrain->getMaterial(0).PointCloud);
                Terrain->setMaterialFlag(video::EMF_WIREFRAME, false);
                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;
            case irr::KEY_KEY_S: // toggle skies
                showBox=!showBox;
                Skybox->setVisible(showBox);
                Skydome->setVisible(!showBox);
                return true;
            case irr::KEY_KEY_X: // toggle debug information
                showDebug=!showDebug;
                Terrain->setDebugDataVisible(showDebug?scene::EDS_BBOX_ALL:scene::EDS_OFF);
                return true;
            default:
                break;
            }
        }

        return false;
    }

private:
    scene::ISceneNode* Terrain;
    scene::ISceneNode* Skybox;
    scene::ISceneNode* Skydome;
    bool showBox;
    bool showDebug;
};

The start of the main function starts like in most other example. We ask the user for the desired renderer and start it up. This time with the advanced parameter handling.

int main()
{
    // ask user for driver
    video::E_DRIVER_TYPE driverType=driverChoiceConsole();
    if (driverType==video::EDT_COUNT)
        return 1;

    // create device with full flexibility over creation parameters
    // you can add more parameters if desired, check irr::SIrrlichtCreationParameters
    irr::SIrrlichtCreationParameters params;
    params.DriverType=driverType;
    params.WindowSize=core::dimension2d<u32>(640, 480);
    IrrlichtDevice* device = createDeviceEx(params);

    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);

const io::path mediaPath = getExampleMediaPath();

// add irrlicht logo
env->addImage(driver->getTexture(mediaPath + "irrlichtlogo3.png"),
    core::position2d<s32>(10,10));

//set other font
env->getSkin()->setFont(env->getFont(mediaPath + "fontlucida.png"));

// add some help text (let's ignore 'P' and 'X' which are more about debugging)
env->addStaticText(
    L"Press 'W' to change wireframe mode\nPress 'D' to toggle detail map\nPress 'S' to toggle skybox/skydome",
    core::rect<s32>(10,421,250,475), true, true, 0, -1, true);

// add camera
scene::ICameraSceneNode* camera =
    smgr->addCameraSceneNodeFPS(0,100.0f,1.2f);

camera->setPosition(core::vector3df(2700*2,255*2,2600*2));
camera->setTarget(core::vector3df(2397*2,343*2,2700*2));
camera->setFarValue(42000.0f);

// 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 first parameter 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 bigger, we change it's scale factor 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(
    mediaPath + "terrain-heightmap.bmp",
    0,                  // parent node
    -1,                 // node id
    core::vector3df(0.f, 0.f, 0.f),     // position
    core::vector3df(0.f, 0.f, 0.f),     // rotation
    core::vector3df(40.f, 4.4f, 40.f),  // scale
    video::SColor ( 255, 255, 255, 255 ),   // vertexColor
    5,                  // maxLOD
    scene::ETPS_17,             // patchSize
    4                   // smoothFactor
    );

terrain->setMaterialFlag(video::EMF_LIGHTING, false);

terrain->setMaterialTexture(0,
        driver->getTexture(mediaPath + "terrain-texture.jpg"));
terrain->setMaterialTexture(1,
        driver->getTexture(mediaPath + "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();

If you need access to the terrain data you can also do this directly via the following code fragment.

scene::CDynamicMeshBuffer* buffer = new scene::CDynamicMeshBuffer(video::EVT_2TCOORDS, video::EIT_16BIT);
terrain->getMeshBufferForLOD(*buffer, 0);
video::S3DVertex2TCoords* data = (video::S3DVertex2TCoords*)buffer->getVertexBuffer().getData();
// Work on data or get the IndexBuffer with a similar call.
(void)data; // disable unused variable warnings
buffer->drop(); // When done drop the buffer again.

To make the user be able to switch between normal and wireframe mode, we create an instance of the event receiver from above and let Irrlicht know about it. In addition, we add the skybox which we already used in lots of Irrlicht examples and a skydome, which is shown mutually exclusive with the skybox by pressing 'S'.

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

scene::ISceneNode* skybox=smgr->addSkyBoxSceneNode(
    driver->getTexture(mediaPath + "irrlicht2_up.jpg"),
    driver->getTexture(mediaPath + "irrlicht2_dn.jpg"),
    driver->getTexture(mediaPath + "irrlicht2_lf.jpg"),
    driver->getTexture(mediaPath + "irrlicht2_rt.jpg"),
    driver->getTexture(mediaPath + "irrlicht2_ft.jpg"),
    driver->getTexture(mediaPath + "irrlicht2_bk.jpg"));
scene::ISceneNode* skydome=smgr->addSkyDomeSceneNode(driver->getTexture(mediaPath + "skydome.jpg"),16,8,0.95f,2.0f);

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

// create event receiver
MyEventReceiver receiver(terrain, skybox, skydome);
device->setEventReceiver(&receiver);

That's it, draw everything.

    int lastFPS = -1;

    while(device->run())
    if (device->isWindowActive())
    {
        driver->beginScene(video::ECBF_COLOR | video::ECBF_DEPTH, video::SColor(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;
            // Also print terrain height of current camera position
            // We can use camera position because terrain is located at coordinate origin
            str += " Height: ";
            str += terrain->getHeight(camera->getAbsolutePosition().X,
                    camera->getAbsolutePosition().Z);

            device->setWindowCaption(str.c_str());
            lastFPS = fps;
        }
    }

    device->drop();
    
    return 0;
}

Now you know how to use terrain in Irrlicht.