A trail in my game...

This is a discussion on A trail in my game... within the C++ Programming forums, part of the General Programming Boards category; Here is my pong game or the beginning of it anyway. I know my collision detection stuff doesn't work right ...

  1. #1
    Registered User zergdeath1's Avatar
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    Sep 2003
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    A trail in my game...

    Here is my pong game or the beginning of it anyway. I know my collision detection stuff doesn't work right and I will fix that later. But when I run this I get a trail behind pongBall. Can someone tell me how to stop this?

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    #include <string.h>
    #include "SDL.h"
    #include <iostream>
    using namespace std;
    ////////////////////////Variables/////////////////
    SDL_Surface *screen;
    SDL_Surface *ball;
    SDL_Surface *lside;
    SDL_Surface *rside;
    SDL_Surface *uside;
    SDL_Surface *dside;
    
    SDL_Rect ballrect;
    SDL_Rect lsiderect;
    SDL_Rect rsiderect;
    SDL_Rect usiderect;
    SDL_Rect dsiderect;
    
    
    int lsidex=0,lsidey=0;
    int rsidex=499,rsidey=0;
    int usidex=0,usidey=0;
    int dsidex=0,dsidey=499;
    /////////////////////Classes//////////////////////
    class Ball{
        public:
            int xpos;
            int ypos;
            int vely;
            int velx;
            Ball(){xpos=250;ypos=250;velx=-1;vely=1;};
            
    };    
    Ball pongBall;
    //////////////////////Function Declarations////////////////
    int LoadScreens();
    int redrawscreen();
    int loadrects();
    int moveball();
    int collisiond();
    
    
    ////////////////////////////Main////////////////////   
    int main(int argc, char*argv[])
    {
      int done=0;
      
      Ball pongBall;
      LoadScreens();
        
      while(done == 0){
      collisiond();
      moveball();  
      loadrects();
      redrawscreen();
    
        SDL_Event event;
    
        while ( SDL_PollEvent(&event) )
        {
          if ( event.type == SDL_QUIT )  {  done = 1;  }
    
          if ( event.type == SDL_KEYDOWN )
          {
            if ( event.key.keysym.sym == SDLK_ESCAPE ) { done = 1; }
          }
        }
    }    
    
      return 0;
    }
    
    /////////////////////Functions////////////////////
    
    int moveball(){
        pongBall.xpos=pongBall.velx+pongBall.xpos;
        pongBall.ypos=pongBall.vely+pongBall.ypos;
    };    
    
    int collisiond(){
        if (pongBall.xpos==0 || pongBall.xpos==499){pongBall.velx=pongBall.velx*-1;};
        if (pongBall.ypos==0 || pongBall.ypos==499){pongBall.vely=pongBall.vely*-1;};    
    };    
    
    int LoadScreens(){
        screen= SDL_SetVideoMode(500,500,32,SDL_HWSURFACE||SDL_DOUBLEBUF);
        ball = SDL_LoadBMP("Pic1.bmp");
        lside = SDL_LoadBMP("larside.bmp");
        rside = SDL_LoadBMP("larside.bmp");
        uside = SDL_LoadBMP("UpaDwnside.bmp");
        dside = SDL_LoadBMP("UpaDwnside.bmp");
    };
    
    int redrawscreen(){
        SDL_BlitSurface(ball,NULL,screen,&ballrect);
        SDL_BlitSurface(lside,NULL,screen,&lsiderect);
        SDL_BlitSurface(rside,NULL,screen,&rsiderect);
        SDL_BlitSurface(uside,NULL,screen,&usiderect);
        SDL_BlitSurface(dside,NULL,screen,&dsiderect);
        SDL_Flip(screen);   
    };
    
    int loadrects(){
        ballrect.x = pongBall.xpos;
        ballrect.y = pongBall.ypos;
        lsiderect.x=lsidex;
        lsiderect.y=lsidey;
        rsiderect.x=rsidex;
        rsiderect.y=rsidey;
        usiderect.x=usidex;
        usiderect.y=usidey;
        dsiderect.x=dsidex;
        dsiderect.y=dsidey;
    };
    Stolen Quote: Buttered Toast always lands butter side down and cats always land on their feet, what happens when you strap buttered Toast to the back of a cat?
    My Quote: Practice Makes Perfect Nobodys Perfect Why Practice?

  2. #2
    Sweet
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    I don't know if your stuck on SDL or not but maybe you should check out allegro I have used both and I like allegro better.
    http://www.loomsoft.net/resources/al...ltut_index.htm is a the tutorial I learned the basics from its very similar to SDL so you should have no problem switching over. Im not sure what compiler you use but http://www.allegro.cc/ is a good site with details on setting it up with dev or msvc(if you use linux im sure your good enough to figure it out yourself )
    Woop?

  3. #3
    Registered User zergdeath1's Avatar
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    Actually I am stuck on SDL because It is what I have been studying and I hope to move on to 3D some time in the future.

    So does anyone know how to get the trail to stop?
    Stolen Quote: Buttered Toast always lands butter side down and cats always land on their feet, what happens when you strap buttered Toast to the back of a cat?
    My Quote: Practice Makes Perfect Nobodys Perfect Why Practice?

  4. #4
    Super Moderator VirtualAce's Avatar
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    Sounds like you are not erasing the old image of the ball. Double buffering should take care of the problem.

  5. #5
    Carnivore ('-'v) Hunter2's Avatar
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    Indeed. You can erase the whole screen and redraw everything, or you can erase the ball and redraw it elsewhere - but if you do either of these, then you'll get flickering, which is solved by using the technique of Double-Buffering.
    Just Google It. √

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