Lesson 5: Fire in OpenGL, Particle Engine
To create a fire/explosion like effect we can use the same particle engine as in the previous tutorial (starfield) but we have to modify the code a little bit.
All particles move upwards; in addition, every particle has to moves at a different speed, and start from the same point.
All code below. You may want to clean up the code a bit, but it demonstrates the principle:
/* * OpenGL Textured Cube * https://talkera.org.cp-in-1.webhostbox.net/opengl/ * http://openglsamples.sf.net * * Compilation trough: * gcc cube2.c -lglut -lGL -lGLU -lSDL -lSDL_image * * Note lSDL_image is added for PNG support! * */ #include#include #include #include #include "SDL/SDL.h" #include /* screen width, height, and bit depth */ #define SCREEN_WIDTH 640 #define SCREEN_HEIGHT 480 #define SCREEN_BPP 16 /* Setup useful booleans */ #define TRUE 1 #define FALSE 0 /* This is our SDL surface */ SDL_Surface *surface; /* Used for rotating the cube */ GLfloat rotationXaxis; GLfloat rotationYaxis; GLfloat rotationZaxis; /* Storage For Textures */ GLuint texture[3]; /* Release resources and quit */ void Quit( int returnCode ) { SDL_Quit( ); exit( returnCode ); } int NR_STARS = 100; float starx[1024],stary[1024],starz[1024]; /* Loads in a bitmap as a GL texture */ int LoadGLTextures( ) { int Status = FALSE; /* Create storage space for the texture */ SDL_Surface *TextureImage[1]; /* Load The Bitmap into Memory */ if ((TextureImage[0] = IMG_Load("data/fire2.jpg"))) { Status = TRUE; glGenTextures( 1, &texture[0] ); glBindTexture( GL_TEXTURE_2D, texture[0] ); glTexImage2D( GL_TEXTURE_2D, 0, 3, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->pixels ); glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR ); glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); } /* Free up some memory */ if ( TextureImage[0] ) SDL_FreeSurface( TextureImage[0] ); // second texture /* Load The Bitmap into Memory */ if ((TextureImage[0] = IMG_Load("data/fire.jpg"))) { Status = TRUE; glGenTextures( 1, &texture[1] ); glBindTexture( GL_TEXTURE_2D, texture[1] ); glTexImage2D( GL_TEXTURE_2D, 0, 3, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->pixels ); glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR ); glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR ); } /* Free up some memory */ if ( TextureImage[0] ) SDL_FreeSurface( TextureImage[0] ); return Status; } /* function to reset our viewport after a window resize */ int resizeWindow( int width, int height ) { /* Height / width ration */ GLfloat ratio; /* Protect against a divide by zero */ if ( height == 0 ) height = 1; ratio = ( GLfloat )width / ( GLfloat )height; /* Setup our viewport. */ glViewport( 0, 0, ( GLint )width, ( GLint )height ); /* * change to the projection matrix and set * our viewing volume. */ glMatrixMode( GL_PROJECTION ); glLoadIdentity( ); /* Set our perspective */ gluPerspective( 45.0f, ratio, 0.1f, 100.0f ); /* Make sure we're chaning the model view and not the projection */ glMatrixMode( GL_MODELVIEW ); /* Reset The View */ glLoadIdentity( ); return( TRUE ); } /* function to handle key press events */ void handleKeyPress( SDL_keysym *keysym ) { switch ( keysym->sym ) { case SDLK_ESCAPE: /* ESC key was pressed */ Quit( 0 ); break; case SDLK_F1: /* F1 key was pressed * this toggles fullscreen mode */ SDL_WM_ToggleFullScreen( surface ); break; default: break; } return; } /* OpenGL initialization function */ int initGL( GLvoid ) { /* Load in the texture */ if ( !LoadGLTextures( ) ) return FALSE; /* Enable Texture Mapping ( NEW ) */ glEnable( GL_TEXTURE_2D ); /* Enable smooth shading */ glShadeModel( GL_SMOOTH ); /* Set the background black */ glClearColor( 0.0f, 0.0f, 0.0f, 0.5f ); /* Depth buffer setup */ glClearDepth( 1.0f ); /* Enables Depth Testing */ glEnable( GL_DEPTH_TEST ); /* The Type Of Depth Test To Do */ glDepthFunc( GL_LEQUAL ); /* Really Nice Perspective Calculations */ glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST ); return( TRUE ); } void initStars() { int i = 0; for (i = 0; i 5) stary[i] = 0; } // drawStar(); /* Draw it to the screen */ SDL_GL_SwapBuffers( ); /* Rotate */ rotationXaxis += 0.3f; rotationYaxis += 0.2f; rotationZaxis += 0.2f; return( TRUE ); } /* https://talkera.org.cp-in-1.webhostbox.net/opengl/ */ int main( int argc, char **argv ) { /* Flags to pass to SDL_SetVideoMode */ int videoFlags; /* main loop variable */ int done = FALSE; /* used to collect events */ SDL_Event event; /* this holds some info about our display */ const SDL_VideoInfo *videoInfo; /* whether or not the window is active */ int isActive = TRUE; /* initialize SDL */ if ( SDL_Init( SDL_INIT_VIDEO ) hw_available ) videoFlags |= SDL_HWSURFACE; else videoFlags |= SDL_SWSURFACE; /* This checks if hardware blits can be done */ if ( videoInfo->blit_hw ) videoFlags |= SDL_HWACCEL; /* Sets up OpenGL double buffering */ SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 ); /* get a SDL surface */ surface = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, videoFlags ); /* Verify there is a surface */ if ( !surface ) { fprintf( stderr, "Video mode set failed: %s\n", SDL_GetError( ) ); Quit( 1 ); } /* initialize OpenGL */ initGL( ); initStars(); /* resize the initial window */ resizeWindow( SCREEN_WIDTH, SCREEN_HEIGHT ); /* wait for events */ while ( !done ) { /* handle the events in the queue */ while ( SDL_PollEvent( &event ) ) { switch( event.type ) { case SDL_ACTIVEEVENT: if ( event.active.gain == 0 ) isActive = FALSE; else isActive = TRUE; break; case SDL_VIDEORESIZE: /* handle resize event */ surface = SDL_SetVideoMode( event.resize.w, event.resize.h, 16, videoFlags ); if ( !surface ) { fprintf( stderr, "Could not get a surface after resize: %s\n", SDL_GetError( ) ); Quit( 1 ); } resizeWindow( event.resize.w, event.resize.h ); break; case SDL_KEYDOWN: /* handle key presses */ handleKeyPress( &event.key.keysym ); break; case SDL_QUIT: /* handle quit requests */ done = TRUE; break; default: break; } } /* draw the scene */ if ( isActive ) drawGLScene( ); } /* clean ourselves up and exit */ Quit( 0 ); /* Should never get here */ return( 0 ); }
A single particle uses the following texture:
