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A tutorial by Max Winkel.

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In this tutorial we'll learn how to use splitscreen (e.g. for racing-games) with Irrlicht. We'll create a viewport divided into 4 parts, with 3 fixed cameras and one user-controlled.

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Ok, let's start with the headers (I think there's nothing to say about it)

#include <irrlicht.h>
#include "driverChoice.h"
#ifdef _MSC_VER
#pragma comment(lib, "Irrlicht.lib")
#endif
//Namespaces for the engine
using namespace irr;
using namespace core;
using namespace video;
using namespace scene;

Now we'll define the resolution in a constant for use in initializing the device and setting up the viewport. In addition we set up a global variable saying splitscreen is active or not.

//Resolution
const int ResX=800;
const int ResY=600;
const bool fullScreen=false;
//Use SplitScreen?
bool SplitScreen=true;

Now we need four pointers to our cameras which are created later:

//cameras

ICameraSceneNode *camera[4]={0,0,0,0};

In our event-receiver we switch the SplitScreen-variable, whenever the user press the S-key. All other events are sent to the FPS camera.

class MyEventReceiver : public IEventReceiver
{
    public:
        virtual bool OnEvent(const SEvent& event)
        {
            //Key S enables/disables SplitScreen
            if (event.EventType == irr::EET_KEY_INPUT_EVENT &&
                event.KeyInput.Key == KEY_KEY_S && event.KeyInput.PressedDown)
            {
                SplitScreen = !SplitScreen;
                return true;
            }
            //Send all other events to camera4
            if (camera[3])
                return camera[3]->OnEvent(event);
            return false;
        }
};

Ok, now the main-function: First, we initialize the device, get the SourceManager and VideoDriver, load an animated mesh from .md2 and a map from .pk3. Because that's old stuff, I won't explain every step. Just take care of the maps position.

int main()
{
    // ask user for driver
    video::E_DRIVER_TYPE driverType=driverChoiceConsole();
    if (driverType==video::EDT_COUNT)
        return 1;
    //Instance of the EventReceiver
    MyEventReceiver receiver;
    //Initialise the engine
    IrrlichtDevice *device = createDevice(driverType,
            dimension2du(ResX,ResY), 32, fullScreen,
            false, false, &receiver);
    if (!device)
        return 1;
    ISceneManager *smgr = device->getSceneManager();
    IVideoDriver *driver = device->getVideoDriver();
    //Load model
    IAnimatedMesh *model = smgr->getMesh("../../media/sydney.md2");
    if (!model)
        return 1;
    IAnimatedMeshSceneNode *model_node = smgr->addAnimatedMeshSceneNode(model);
    //Load texture
    if (model_node)
    {
        ITexture *texture = driver->getTexture("../../media/sydney.bmp");
        model_node->setMaterialTexture(0,texture);
        model_node->setMD2Animation(scene::EMAT_RUN);
        //Disable lighting (we've got no light)
        model_node->setMaterialFlag(EMF_LIGHTING,false);
    }
    //Load map
    device->getFileSystem()->addFileArchive("../../media/map-20kdm2.pk3");
    IAnimatedMesh *map = smgr->getMesh("20kdm2.bsp");
    if (map)
    {
        ISceneNode *map_node = smgr->addOctreeSceneNode(map->getMesh(0));
        //Set position
        map_node->setPosition(vector3df(-850,-220,-850));
    }

Now we create our four cameras. One is looking at the model from the front, one from the top and one from the side. In addition there's a FPS-camera which can be controlled by the user.

// Create 3 fixed and one user-controlled cameras
//Front
camera[0] = smgr->addCameraSceneNode(0, vector3df(50,0,0), vector3df(0,0,0));
//Top
camera[1] = smgr->addCameraSceneNode(0, vector3df(0,50,0), vector3df(0,0,0));
//Left
camera[2] = smgr->addCameraSceneNode(0, vector3df(0,0,50), vector3df(0,0,0));
//User-controlled
camera[3] = smgr->addCameraSceneNodeFPS();
// don't start at sydney's position
if (camera[3])
    camera[3]->setPosition(core::vector3df(-50,0,-50));

Create a variable for counting the fps and hide the mouse:

//Hide mouse
device->getCursorControl()->setVisible(false);
//We want to count the fps
int lastFPS = -1;

There wasn't much new stuff - till now! Only by defining four cameras, the game won't be splitscreen. To do this you need several steps:

Set the viewport to the whole screen
Begin a new scene (Clear screen)
The following 3 steps are repeated for every viewport in the splitscreen
- Set the viewport to the area you wish
- Activate the camera which should be "linked" with the viewport
- Render all objects
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If you have a GUI:
- Set the viewport the whole screen
- Display the GUI
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End scene

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Sounds a little complicated, but you'll see it isn't:

while(device->run())
{
    //Set the viewpoint to the whole screen and begin scene
    driver->setViewPort(rect<s32>(0,0,ResX,ResY));
    driver->beginScene(true,true,SColor(255,100,100,100));
    //If SplitScreen is used
    if (SplitScreen)
    {
        //Activate camera1
        smgr->setActiveCamera(camera[0]);
        //Set viewpoint to the first quarter (left top)
        driver->setViewPort(rect<s32>(0,0,ResX/2,ResY/2));
        //Draw scene
        smgr->drawAll();
        //Activate camera2
        smgr->setActiveCamera(camera[1]);
        //Set viewpoint to the second quarter (right top)
        driver->setViewPort(rect<s32>(ResX/2,0,ResX,ResY/2));
        //Draw scene
        smgr->drawAll();
        //Activate camera3
        smgr->setActiveCamera(camera[2]);
        //Set viewpoint to the third quarter (left bottom)
        driver->setViewPort(rect<s32>(0,ResY/2,ResX/2,ResY));
        //Draw scene
        smgr->drawAll();
        //Set viewport the last quarter (right bottom)
        driver->setViewPort(rect<s32>(ResX/2,ResY/2,ResX,ResY));
    }
    //Activate camera4
    smgr->setActiveCamera(camera[3]);
    //Draw scene
    smgr->drawAll();
    driver->endScene();

As you can probably see, the image is rendered for every viewport separately. That means, that you'll loose much performance. Ok, if you're asking "How do I have to set the viewport + to get this or that screen?", don't panic. It's really easy: In the rect-function you define 4 coordinates:

X-coordinate of the corner left top
Y-coordinate of the corner left top
X-coordinate of the corner right bottom
Y-coordinate of the corner right bottom

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That means, if you want to split the screen into 2 viewports you would give the following coordinates:

1st viewport: 0,0,ResX/2,ResY
2nd viewport: ResX/2,0,ResX,ResY

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If you didn't fully understand, just play around with the example to check out what happens.

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Now we just view the current fps and shut down the engine, when the user wants to:

        //Get and show fps
        if (driver->getFPS() != lastFPS)
        {
            lastFPS = driver->getFPS();
            core::stringw tmp = L"Irrlicht SplitScreen-Example (FPS: ";
            tmp += lastFPS;
            tmp += ")";
            device->setWindowCaption(tmp.c_str());
        }
    }
    //Delete device
    device->drop();
    return 0;
}

That's it! Just compile and play around with the program. Note: With the S-Key you can switch between using splitscreen and not.

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