1. 111 Introduction to OGRE3D Programming: Main Loop

2. 22 Major part of call graph BaseApplication::go() BaseApplication::setup() Root::startRendering() Root::renderOneFrame() Root::_updateAllRenderTargets(); Root::_fireFrameStarted()Root::_fireFrameEnded();

3. 3 Main program int main(int argc, char **argv) { BaseApplication *MyGameApp = new BaseApplication; try { MyGameApp  go(); } catch( Exception& e ) { … } return 1; }

4. virtual void BaseApplication::go(void) { if (!setup()) return; mRoot->startRendering(); // clean up destroyScene(); } The implementation of go()

5. The implementation of setup() The function setup() instantiates mRoot, setups resources, loads plugins, creates scene and creates frame listener. mRoot = new Ogre::Root(mPluginsCfg); setupResources(); bool carryOn = configure(); if (!carryOn) return false; chooseSceneManager(); createCamera(); createViewports(); createResourceListener(); loadResources(); createScene(); createFrameListener();

6. 6 Major functions (1/3) Root::startRendering() { assert(mActiveRenderer != 0); mActiveRenderer->_initRenderTargets(); clearEventTimes(); // Infinite loop, until broken out of by frame listeners // or break out by calling queueEndRendering() mQueuedEnd = false; while( !mQueuedEnd ) { //Pump messages in all registered RenderWindow windows WindowEventUtilities::messagePump(); if ( !renderOneFrame() ) break; }

7. 7 Major functions (2/3) bool Root::renderOneFrame(void) { if( !_fireFrameStarted() ) return false; _updateAllRenderTargets(); return _fireFrameEnded(); } class myFrameListener : public FrameListener { public: bool frameStarted (const FrameEvent &evt); bool frameRenderingQueued( const FrameEvent &evt); bool frameEnded (const FrameEvent &evt); }; bool myFrameListener::frameStarted( const FrameEvent &evt) { // cool stuff to do before a frame is rendered return true; } //define frameRenderingQueued here bool myFrameListener::frameEnded( const FrameEvent &evt) { // cool stuff to do after a frame is rendered return true; }

8. bool Root::_fireFrameStarted(FrameEvent& evt) bool Root::_fireFrameStarted(FrameEvent& evt) OgreProfileBeginGroup("Frame", OGREPROF_GENERAL); // Remove all marked listeners … // Tell all listeners for ( i= mFrameListeners.begin(); i != mFrameListeners.end(); ++i ) { if ( !(*i)  frameStarted(evt) ) if ( !(*i)  frameStarted(evt) ) return false; return false; } return true;

9. bool Root::_updateAllRenderTargets(void) // update all targets but don't swap buffers mActiveRenderer->_updateAllRenderTargets(false); // give client app opportunity to use queued GPU time bool ret = _fireFrameRenderingQueued(); // This belongs here, as all render targets must be updated // before events are triggered, otherwise targets could be // mismatched. This could produce artifacts, e.g. with shadows. …… return ret;

10. bool Root::_fireFrameRenderingQueued(FrameEvent& evt) // Increment next frame number ++mNextFrame; // Remove all marked listeners …… // Tell all listeners for ( i= mFrameListeners.begin(); i != mFrameListeners.end(); ++i ) { if ( !(*i)->frameRenderingQueued( evt ) ) if ( !(*i)->frameRenderingQueued( evt ) ) return false; return false;} return true;

11. bool Root::_fireFrameEnded(FrameEvent& evt) bool Root::_fireFrameEnded(FrameEvent& evt) // Remove all marked listeners …… // Tell all listeners bool ret = true; for ( i= mFrameListeners.begin(); i != mFrameListeners.end(); ++i ) { if ( !(*i)->frameEnded(evt) ) { if ( !(*i)->frameEnded(evt) ) { ret = false; ret = false;break;}} // Tell buffer manager to free temp buffers used this frame return ret;

12. Remove all marked Listener set ::type::iterator i; for (i = mRemovedFrameListeners.begin(); i != mRemovedFrameListeners.end(); i != mRemovedFrameListeners.end(); i++) i++){ mFrameListeners.erase(*i); mFrameListeners.erase(*i);}mRemovedFrameListeners.clear();

13. 13 Major functions (3/3) bool myFrameListener::frameStarted(const FrameEvent& evt) { if(mWindow->isClosed()) return false;...... //Need to capture/update each device mKeyboard->capture(); mMouse->capture(); if( mJoy ) mJoy->capture();... handleKeyEvent(evt); handleMouseEvent(evt);... return true; } } code for game management and update of game state based on FrameEvent evt.

14. 14 Major part of call graph GameApplication::go() GameApplication::setup() Root::startRendering() Root::renderOneFrame() Root::_updateAllRenderTargets(); Root::_fireFrameStarted()Root::_fireFrameEnded();

15. 15 Frame listeners are the only way we can invoke your own code during the Ogre render loop when using the startRendering() method. A frame listener is simply a class that implements the FrameListener interface, and is just a callback that allows OGRE to invoke our code at the beginning and/or end of each. Frame listener

16. 16 Use ExampleApplication and ExampleFrameListener Demo: main_loop In the main.cpp file, we have: class GameApplication: public ExampleApplication { public: GameApplication() {} void createScene() {} }; GameApplication *app = new GameApplication; int main(int argc, char **argv) { try { app->go(); } catch( Exception& e ) { ……. }

17. 17 Object-Oriented Graphics Rendering Engine ( OGRE 3D) - The Main Program

18. FrameStarted 18 bool myFrameListener::frameStarted(const FrameEvent& evt) { if(mWindow->isClosed()) return false;... //Need to capture/update each device mKeyboard->capture(); mMouse->capture(); if( mJoy ) mJoy->capture();... handleKeyEvent(evt); handleMouseEvent(evt);... moveMainChar(evt); updateCreaturesAction(evt);... return true; } } code for game management and update of game state based on FrameEvent evt.

19. moveMainChar 19 void moveMainChar(const FrameEvent& evt) { mCameraNode->yaw(mRotX); // move the head node along the camera viewing direction const Quaternion q = mCameraNode->getOrientation(); mCameraNode->setOrientation(q); SceneNode *node = mHeadNode->getSceneNode(); node->setOrientation(q); node->translate( q*(-mTranslateVector) ); // maintain the distance between the camera and mHeadNode const Vector3 v3 = node->getPosition(); Vector3 cv = v3; Vector3 hv = Vector3(0.0, 0.0, -1.0); hv = q*hv; float d0 = -mCamerViewDistanceFromMainChar; float d1 = 30; mCameraNode->setPosition(cv-hv*d0+Vector3(0.0, d1, 0.0)); }

20. updateCreatureActions 20 void updateCreaturesAction(const FrameEvent& evt) { if (mRobot) { mRobot->checkAlive(evt); } if (mRobot && mHeadNode) { mRobot->UpdateAction(evt, mHeadNode); }

21. FrameEvent 21 namespace Ogre { struct FrameEvent { /** Elapsed time in seconds since the last event. This gives you time between frame start & frame end, and between frame end and next frame start. @remarks This may not be the elapsed time but the average elapsed time between recently fired events. */ Real timeSinceLastEvent; /** Elapsed time in seconds since the last event of the same type, i.e. time for a complete frame. @remarks This may not be the elapsed time but the average elapsed time between recently fired events of the same type. */ Real timeSinceLastFrame; };

22. Introduction to dynamic-link library (DLL) On Windows On Windows Microsoft’s implementation of shared library Microsoft’s implementation of shared library File format same as for the Windows EXE files File format same as for the Windows EXE files Containing Containing –Code –Data –Resources, –or in any combination 22

23. Symbol resolution and binding Each function exported by a DLL is identified by a numeric ordinal and optionally a name Each function exported by a DLL is identified by a numeric ordinal and optionally a name Functions can be imported from a DLL either by ordinal or by a name Functions can be imported from a DLL either by ordinal or by a name The ordinal represents the position of the functions address pointer in the DLL Export Address table The ordinal represents the position of the functions address pointer in the DLL Export Address table 23

24. Symbol resolution and binding Ordinal: subject to change Ordinal: subject to change Names: preserved across different Windows releases Names: preserved across different Windows releases 24

25. 25 Load-time dynamic linking Use the information the linker placed in the file to locate the names of the DLLs that are used by the process Fail to locate a required DLL -> terminate the process and report the error Locate successfully -> map the DLL into the virtual address space of the process

26. 26 Load-time dynamic linking - Call a DLL function explicitly. - The application must be linked with the import library myMessage.lib. extern "C" int __cdecl myMessage(LPWSTR); // a function from a DLL int main(VOID) { int Ret = 1; Ret = myMessage (L“Message\n”); return Ret; }

27. 27 Explicit run-time linking LoadLibrary (or LoadLibraryEx): explicitly load at run time LoadLibrary (or LoadLibraryEx): explicitly load at run time GetProcAddress: lookup exported symbols by name FreeLibrary: unload the DLL

28. Example: creating a DLL 28 #ifdef __cplusplus // If used by C++ code, extern "C" { // we need to export the C interface #endif __declspec(dllexport) void* createSceneCreator() { … return static_cast (new DemoApp);} #ifdef __cplusplus } #endif

29. Module definition file 29 (.def) file : a text file that contains statements defining an executable (.exe) file or dynamic-link library (DLL). Some commands: LIBRARY: LIBRARY: Specify the internal name of the DLL EXPORTS: M EXPORTS: Make one or more definitions available as exports to other applications Syntax of an export definition: entryname[=internalname] [@ordinal[NONAME]]

30. Creating a DLL: Setup module definition file 30 Project>properties->Linker-> input->module definition file Content of sceneCreator.def LIBRARY sceneCreator EXPORTS createSceneCreator @1

31. Explicit run-time linking DLL 31 HINSTANCE hdll = NULL; typedef void* (*pvFunctv)(); pvFunctv sceneCreator; hdll = LoadLibrary(TEXT("./dll/sceneCreator.dll")); if (hdll) { … } else { ……; return; } sceneCreator = (pvFunctv) (GetProcAddress( hdll, "createSceneCreator" ) ); DemoApp *app = static_cast ( sceneCreator() );

32. Useful links for DLL About DLL: About DLL: http://msdn2.microsoft.com/en- us/library/ms686912(VS.85).aspx Module definition file: http://msdn2.microsoft.com/en- us/library/ms923590.aspx Module definition file: http://msdn2.microsoft.com/en- us/library/ms923590.aspx 32