hi I have been going thrugh sdl tutoials and what the below program initially did was create 2 dot objects one moved via the arrow keys via events and the other did nothng and if one dot hit the other they correctly collided. Anyway I decided if I want to get a better understaning I would try and immplement a part that made the static dot bunce up and down on the y axis , this one wouldnt have events it would just bounce up and down indefinatelky and correctly handle a collision .........I couldnt get that working so I tried to move the dot to the bottom of the screen .......it moves but I dont see the movement in progress if you get what i mean .......by the time the screen shows the movement has been made. Can anyone help me get this ball bouncing or even just moving gradually from y 0 to y300 or something
thanks
david
Code:#include "SDL/SDL.h" #include <string> #include <stdio.h> #include <vector> #include "SDL/SDL_image.h" //set global vars for screen width height and bts per pixel they are constants const int SCREEN_WIDTH = 640; const int SCREEN_HEIGHT = 480; const int SCREEN_BPP = 32; //The frame rate const int FRAMES_PER_SECOND = 20; //set dot attribs const int dot_h = 20; const int dot_w = 20; //set global surfaces SDL_Surface *dot = NULL; SDL_Surface *screen = NULL; //The event structure SDL_Event event; class Dot { private: //the offsets of the dot int x,y; //the velocity of dots int xVel,yVel; //The collision boxes of the dot std::vector<SDL_Rect> box; void move_collision_box(); public: //init dot objects vars in default constructor Dot(int X,int Y); //handles key presses and adjusts dots velocity void handle_input(); void handle_inputboing(); //moves the dot void move(std::vector<SDL_Rect>&rects); void bounce(std::vector<SDL_Rect>&rects); //Shows the dot on the screen void show(); //Gets the collision boxes returns a rect std::vector<SDL_Rect> &get_rects(); }; Dot::Dot(int X,int Y) { //Initialize the offsets x = X; y = Y; //Initialize the velocity xVel = 0; yVel = 0; //resize vector to 11 to account for each row of the circles collision rect box.resize(11); //Initialize the collision boxes' width and height box[ 0 ].w = 6; box[ 0 ].h = 1; box[ 1 ].w = 10; box[ 1 ].h = 1; box[ 2 ].w = 14; box[ 2 ].h = 1; box[ 3 ].w = 16; box[ 3 ].h = 2; box[ 4 ].w = 18; box[ 4 ].h = 2; box[ 5 ].w = 20; box[ 5 ].h = 6; box[ 6 ].w = 18; box[ 6 ].h = 2; box[ 7 ].w = 16; box[ 7 ].h = 2; box[ 8 ].w = 14; box[ 8 ].h = 1; box[ 9 ].w = 10; box[ 9 ].h = 1; box[ 10 ].w = 6; box[ 10 ].h = 1; //Move the collision boxes to their proper spot move_collision_box(); } void apply_surface( int x, int y, SDL_Surface* source, SDL_Surface* destination, SDL_Rect* clip = NULL ) { //Holds offsets SDL_Rect offset; //Get offsets offset.x = x; offset.y = y; //Blit SDL_BlitSurface( source, clip, destination, &offset ); } void Dot::show() { //Show the dot apply_surface( x, y, dot, screen ); } void Dot::move_collision_box() { int row = 0; for(int set = 0; set < box.size(); set++) { //center the collisionbox box[set].x = x+(dot_w - box[set].w)/2; box[set].y = y+row; //move the row offset down the height of the collision box row = row + box[set].h; } } void Dot::handle_inputboing() { while(y < 90){ //Adjust the velocity y=y +1; //wait y = y + 1; } } void Dot::handle_input() { //if a key was pressed if(event.type == SDL_KEYDOWN) { //switch arrow keys if arrow used adjust dots direction dependant on the arrow key pressed switch(event.key.keysym.sym) //key object->key->key symbol obj container->actual symbol { case SDLK_UP: yVel = yVel - 1;break; //It is -1 because y axis goes bottom left to top left 20 19 18 case SDLK_DOWN: yVel = yVel + 1;break; case SDLK_LEFT: xVel = xVel - 1;break; case SDLK_RIGHT: xVel = xVel + 1;break; } } else if(event.type == SDL_KEYUP) //if key was release we dont want prog to do nothing make shape move same again so it moves fluently { //Adjust the velocity switch( event.key.keysym.sym ) { case SDLK_UP: yVel = yVel + 1;break; //It is -1 because y axis goes bottom left to top left 20 19 18 case SDLK_DOWN: yVel = yVel - 1;break; case SDLK_LEFT: xVel = xVel + 1;break; case SDLK_RIGHT: xVel = xVel - 1;break; } } } bool check_collision( std::vector<SDL_Rect> &A, std::vector<SDL_Rect> &B ) { //The sides of the rectangles int leftA, leftB; int rightA, rightB; int topA, topB; int bottomA, bottomB; //Go through the A boxes for( int Abox = 0; Abox < A.size(); Abox++ ) { //Calculate the sides of rect A leftA = A[ Abox ].x; rightA = A[ Abox ].x + A[ Abox ].w; topA = A[ Abox ].y; bottomA = A[ Abox ].y + A[ Abox ].h; //Go through the B boxes for( int Bbox = 0; Bbox < B.size(); Bbox++ ) { //Calculate the sides of rect B leftB = B[ Bbox ].x; rightB = B[ Bbox ].x + B[ Bbox ].w; topB = B[ Bbox ].y; bottomB = B[ Bbox ].y + B[ Bbox ].h; //If no sides from A are outside of B if( ( ( bottomA <= topB ) || ( topA >= bottomB ) || ( rightA <= leftB ) || ( leftA >= rightB ) ) == false ) { //A collision is detected return true; } } } //If neither set of collision boxes touched return false; } void Dot::move(std::vector<SDL_Rect> &aRect) { //Move the dot left or right x += xVel; //Move the collision boxes move_collision_box(); //If the dot went too far to the left or right or has collided with the other dot if( ( x < 0 ) || ( x + dot_w > SCREEN_WIDTH ) || ( check_collision( box, aRect ) ) ) { //Move back x -= xVel; move_collision_box(); } //Move the dot up or down y += yVel; //Move the collision boxes move_collision_box(); //every time dot moves collision box moves //If the dot went too far up or down or has collided with the other dot if( ( y < 0 ) || ( y + dot_h > SCREEN_HEIGHT ) || ( check_collision( box, aRect ) ) ) { //Move back y -= yVel; move_collision_box(); } } void Dot::bounce(std::vector<SDL_Rect> &aRect) { bool bounce = true; y = yVel +30; //If the dot went too far up or down or has collided with the other dot if( check_collision( box, aRect ) ) { //Move back y -= yVel; move_collision_box(); } } std::vector<SDL_Rect>& Dot::get_rects() { return box; } class Timer { private: int startTicks; int TicksAtPause; //timer status bool paused; bool started; public: //initialises timer object variables Timer(); void start(); void stop(); void pause(); void unpause(); //get the number of ticks since timer started or was paused int getTicks(); //Checks the status of the timer bool is_started(); bool is_paused(); }; Timer::Timer() { startTicks = 0; TicksAtPause = 0; started = false; paused = false; } void Timer::start() { started = true; paused = false; //Get the current clock time startTicks = SDL_GetTicks(); } void Timer::stop() { started = false; paused = false; } void Timer::pause() { //iuf timer is currently running if( ( started == true ) && ( paused == false ) ) { //Pause the timer paused = true; //then get the number of ticks - the start ticks to get the ticks exactly when the timer was paused at TicksAtPause = SDL_GetTicks() - startTicks; } } void Timer::unpause() { //If the timer is paused if( paused == true ) { //Unpause the timer paused = false; //Reset the starting ticks TicksAtPause = SDL_GetTicks() - TicksAtPause; //Reset the paused ticks TicksAtPause = 0; } } int Timer::getTicks() { //If the timer is running if( started == true ) { //If the timer is paused if( paused == true ) { //Return the number of ticks when the the timer was paused return TicksAtPause; } else { //Return the current time minus the start time return SDL_GetTicks() - startTicks; } } //If the timer isn't running return 0; } SDL_Surface *load_image( std::string filename ) { //The image that's loaded SDL_Surface* loadedImage = NULL; //The optimized surface that will be used SDL_Surface* optimizedImage = NULL; //Load the image loadedImage = IMG_Load( filename.c_str() ); //If the image loaded if( loadedImage != NULL ) { //Create an optimized surface optimizedImage = SDL_DisplayFormat( loadedImage ); //Free the old surface SDL_FreeSurface( loadedImage ); //If the surface was optimized if( optimizedImage != NULL ) { //Color key surface SDL_SetColorKey( optimizedImage, SDL_RLEACCEL | SDL_SRCCOLORKEY, SDL_MapRGB( optimizedImage->format, 0, 0xFF, 0xFF ) ); } } //Return the optimized surface return optimizedImage; } //int SDL_Init(Uint32 flags); bool startsdl() { //init sdl and check if started ok if not retuen false if(SDL_Init(SDL_INIT_EVERYTHING) == -1) { return false; } return true; } bool setup_screen() { screen = SDL_SetVideoMode(SCREEN_WIDTH,SCREEN_HEIGHT,SCREEN_BPP,SDL_SWSURFACE); if(screen == NULL) { return false; } //set window caption SDL_WM_SetCaption("Boucy Ball vs moving dot",NULL); return true; } bool load_files() { //Load the dot image dot = load_image( "dot.bmp" ); //If there was a problem in loading the dot if( dot == NULL ) { return false; } //If everything loaded fine return true; } void quitsdl() { SDL_Quit(); } bool Timer::is_started() { return started; } bool Timer::is_paused() { return paused; } int main(int argc, char *args[]) { //quit prog status bool quit = false; //make the dots Dot abdot(50,50); Dot movydot(0,0); //setup the timer Timer fps; //init sdl if(startsdl() == false) { printf("sdl init failed \n"); return 1; } //create screen and test if(setup_screen() == false) { printf("Screen setup crashed! \n\n"); return 1; } //Load the files if( load_files() == false ) { return 1; } printf("sdl init worked \n"); printf("screen setup is ok! \n"); printf("images loaded to screen! \n"); //game loop while(quit == false) { //1st start and sort frame rate fps.start(); //do condiotion via event poller to handle user events //while there events to handle //there will be no events first time round so this while will be skipped initially while(SDL_PollEvent(& event) ) { //handle events for the user movable dot movydot.handle_input(); //if the user has Xed out the window if(event.type == SDL_QUIT) { //set quit flag to true quit = true; } } //fill the screen white screen->clip_rect is the rect on the screen you want to fill SDL_FillRect(screen,&screen->clip_rect,SDL_MapRGB(screen->format,0xFF,0xFF,0xFF)); movydot.move(abdot.get_rects()); //? get rects makes my 2nd dot the same as my first //Show the dots on the screen abdot.handle_inputboing(); abdot.bounce(abdot.get_rects()); abdot.show(); movydot.show(); //Update the screen if( SDL_Flip( screen ) == -1 ) { return 1; } //Cap the frame rate while( fps.getTicks() < 1000 / FRAMES_PER_SECOND ) { //wait } } //Clean up quitsdl(); return 0; }
