Introduction to OGRE 3 D Programming Main Loop

Introduction to OGRE 3 D Programming: Main Loop 1

Major part of call graph Base. Application: : go() Base. Application: : setup() Root: : start. Rendering() Root: : render. One. Frame() Root: : _fire. Frame. Started() Root: : _fire. Frame. Ended(); Root: : _update. All. Render. Targets(); 2

Main program int main(int argc, char **argv) { Base. Application *My. Game. App = new Base. Application; try { My. Game. App go(); } catch( Exception& e ) { …… } return 1; } 3

The implementation of go() virtual void Base. Application: : go(void) { if (!setup()) return; m. Root->start. Rendering(); // clean up destroy. Scene(); }

The implementation of setup() The function setup() instantiates m. Root, setups resources, loads plugins, creates scene and creates frame listener. m. Root = new Ogre: : Root(m. Plugins. Cfg); setup. Resources(); bool carry. On = configure(); if (!carry. On) return false; choose. Scene. Manager(); create. Camera(); create. Viewports(); create. Resource. Listener(); load. Resources(); create. Scene(); create. Frame. Listener();

Major functions (1/3) Root: : start. Rendering() { assert(m. Active. Renderer != 0); m. Active. Renderer->_init. Render. Targets(); clear. Event. Times(); // Infinite loop, until broken out of by frame listeners // or break out by calling queue. End. Rendering() m. Queued. End = false; while( !m. Queued. End ) { //Pump messages in all registered Render. Window windows Window. Event. Utilities: : message. Pump(); if ( !render. One. Frame() ) break; } } 6

Major functions (2/3) bool Root: : render. One. Frame(void) class my. Frame. Listener : { public Frame. Listener { if( !_fire. Frame. Started() ) public: bool frame. Started (const Frame. Event &evt); return false; bool frame. Rendering. Queued( const Frame. Event &evt); _update. All. Render. Targets(); bool frame. Ended (const Frame. Event &evt); return _fire. Frame. Ended(); } }; bool my. Frame. Listener: : frame. Started( const Frame. Event &evt) { // cool stuff to do before a frame is rendered return true; } //define frame. Rendering. Queued here bool my. Frame. Listener: : frame. Ended( const Frame. Event &evt) { // cool stuff to do after a frame is rendered return true; } 7

bool Root: : _fire. Frame. Started(Frame. Event& evt) Ogre. Profile. Begin. Group("Frame", OGREPROF_GENERAL); // Remove all marked listeners … // Tell all listeners for ( i= m. Frame. Listeners. begin(); i != m. Frame. Listeners. end(); ++i ) { if ( !(*i) frame. Started(evt) ) return false; } return true;

bool Root: : _update. All. Render. Targets(void) // update all targets but don't swap buffers m. Active. Renderer->_update. All. Render. Targets(false); // give client app opportunity to use queued GPU time bool ret = _fire. Frame. Rendering. Queued(); // 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;

bool Root: : _fire. Frame. Rendering. Queued(Frame. Event& evt) // Increment next frame number ++m. Next. Frame; // Remove all marked listeners …… // Tell all listeners for ( i= m. Frame. Listeners. begin(); i != m. Frame. Listeners. end(); ++i ) { if ( !(*i)->frame. Rendering. Queued( evt ) ) return false; } return true;

bool Root: : _fire. Frame. Ended(Frame. Event& evt) // Remove all marked listeners …… // Tell all listeners bool ret = true; for ( i= m. Frame. Listeners. begin(); i != m. Frame. Listeners. end(); ++i ) { if ( !(*i)->frame. Ended(evt) ) { ret = false; break; } } // Tell buffer manager to free temp buffers used this frame return ret;

Remove all marked Listener set<Frame. Listener*>: : type: : iterator i; for ( i = m. Removed. Frame. Listeners. begin(); i != m. Removed. Frame. Listeners. end(); i++) { m. Frame. Listeners. erase(*i); } m. Removed. Frame. Listeners. clear();

Major functions (3/3) bool my. Frame. Listener: : frame. Started(const Frame. Event& evt) { if(m. Window->is. Closed()) return false; . . . //Need to capture/update each device m. Keyboard->capture(); m. Mouse->capture(); if( m. Joy ) m. Joy->capture(); . . . handle. Key. Event(evt); handle. Mouse. Event(evt); . . . . return true; } } code for game management and update of game state based on Frame. Event evt. 13

Major part of call graph Game. Application: : go() Game. Application: : setup() Root: : start. Rendering() Root: : render. One. Frame() Root: : _fire. Frame. Started() Root: : _fire. Frame. Ended(); Root: : _update. All. Render. Targets(); 14

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

Demo: main_loop Use Example. Application and Example. Frame. Listener In the main. cpp file, we have: class Game. Application: public Example. Application { public: Game. Application() {} void create. Scene() {} }; Game. Application *app = new Game. Application; int main(int argc, char **argv) { try { app->go(); } catch( Exception& e ) { ……. } } 16

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

Frame. Started bool my. Frame. Listener: : frame. Started(const Frame. Event& evt) { if(m. Window->is. Closed()) return false; . . . //Need to capture/update each device m. Keyboard->capture(); m. Mouse->capture(); if( m. Joy ) m. Joy->capture(); . . . handle. Key. Event(evt); handle. Mouse. Event(evt); . . . move. Main. Char(evt); code for game management update. Creatures. Action(evt); and update of game state based. . . on Frame. Event evt. . . } return true; } 18

move. Main. Char void move. Main. Char(const Frame. Event& evt) { m. Camera. Node->yaw(m. Rot. X); // move the head node along the camera viewing direction const Quaternion q = m. Camera. Node->get. Orientation(); m. Camera. Node->set. Orientation(q); Scene. Node *node = m. Head. Node->get. Scene. Node(); node->set. Orientation(q); node->translate( q*(-m. Translate. Vector) ); // maintain the distance between the camera and m. Head. Node const Vector 3 v 3 = node->get. Position(); Vector 3 cv = v 3; Vector 3 hv = Vector 3(0. 0, -1. 0); hv = q*hv; float d 0 = -m. Camer. View. Distance. From. Main. Char; float d 1 = 30; m. Camera. Node->set. Position(cv-hv*d 0+Vector 3(0. 0, d 1, 0. 0)); } 19

update. Creature. Actions void update. Creatures. Action(const Frame. Event& evt) { if (m. Robot) { m. Robot->check. Alive(evt); } if (m. Robot && m. Head. Node) { m. Robot->Update. Action(evt, m. Head. Node); } } 20

Frame. Event namespace Ogre { struct Frame. Event { /** 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 time. Since. Last. Event; /** 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 time. Since. Last. Frame; }; }; 21

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

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

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

Load-time dynamic linking n 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 n Locate successfully -> map the DLL into the virtual address space of the process n 25

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

Explicit run-time linking n Load. Library (or Load. Library. Ex): explicitly load at run time n Get. Proc. Address: lookup exported symbols by name n Free. Library: unload the DLL 27

Example: creating a DLL #ifdef __cplus // If used by C++ code, extern "C" { // we need to export the C interface #endif __declspec(dllexport) void* create. Scene. Creator() { …… return static_cast< void* > (new Demo. App); } #ifdef __cplus } #endif 28

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

Creating a DLL: Setup module definition file Project>properties->Linker-> input->module definition file Content of scene. Creator. def LIBRARY scene. Creator EXPORTS create. Scene. Creator @1 30

Explicit run-time linking DLL HINSTANCE hdll = NULL; typedef void* (*pv. Functv)(); pv. Functv scene. Creator; hdll = Load. Library(TEXT(". /dll/scene. Creator. dll")); if (hdll) { … } else { ……; return; } scene. Creator = (pv. Functv) (Get. Proc. Address( hdll, "create. Scene. Creator" ) ); Demo. App *app = static_cast< Demo. App* > ( scene. Creator() ); 31

Useful links for DLL n About DLL: http: //msdn 2. microsoft. com/enus/library/ms 686912(VS. 85). aspx n Module definition file: http: //msdn 2. microsoft. com/enus/library/ms 923590. aspx 32