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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)

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#include <irrlicht.h>
-#include "driverChoice.h"
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-#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;
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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.

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//Resolution
-const int ResX=800;
-const int ResY=600;
-const bool fullScreen=false;
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-//Use SplitScreen?
-bool SplitScreen=true;
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Now we need four pointers to our cameras which are created later:

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//cameras
-ICameraSceneNode *camera[4]={0,0,0,0};
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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.

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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;
-        }
-};
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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.

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int main()
-{
-    // ask user for driver
-    video::E_DRIVER_TYPE driverType=driverChoiceConsole();
-    if (driverType==video::EDT_COUNT)
-        return 1;
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-    //Instance of the EventReceiver
-    MyEventReceiver receiver;
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-    //Initialise the engine
-    IrrlichtDevice *device = createDevice(driverType,
-            dimension2du(ResX,ResY), 32, fullScreen,
-            false, false, &receiver);
-    if (!device)
-        return 1;
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-    ISceneManager *smgr = device->getSceneManager();
-    IVideoDriver *driver = device->getVideoDriver();
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-    //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);
-    }
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-    //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));
-    }
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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.

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    // 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));
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Create a variable for counting the fps and hide the mouse:

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

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Set the viewport to the whole screen
Begin a new scene (Clear screen)

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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:

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    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();
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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:

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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:

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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:

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        //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;
-}
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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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