StackOverflow2013

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POCan't redraw an image in space
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copied!<p>I am getting some practice with SDL. I currently am drawing space with classes star, sun, and earth. I can get everything to render to the screen but when I move the sun with the right arrow key, I can't figure out how to delete the old sun to simulate that the view is rotating around the sun. It just creates a big line across the screen. I think I need to clear the screen, redraw the stars, sun, and earth every time the key is down. However, I can't redraw the stars because they fall out of scope and if I recreate them they will be in a different position since I use rand() to randomize their locations. I have hit a big wall and would appreciate any advice. </p> <p>The code:</p> <pre><code>// Planet.cpp : Defines the entry point for the console application. // #include "stdafx.h" #include <SDL.h> #include <SDL_gfxPrimitives.h> #include <stdlib.h> #include <time.h> class Star { private: int x,y,rad,r,g,b,a; SDL_Surface* screen; public: Star(SDL_Surface* sc, int xx, int yy, int ra, int rr, int gg, int bb, int aa){screen=sc;x=xx;y=yy;rad=ra;r=rr;g=gg;b=bb;a=aa;} ~Star(){} void Show() { filledCircleRGBA(screen, x, y, rad, r, g, b, a); } }; class Sun { private: int x,y,rad,r,g,b,a; SDL_Surface* screen; public: Sun(SDL_Surface* sc, int xx, int yy, int ra, int rr, int gg, int bb, int aa){screen=sc;x=xx;y=yy;rad=ra;r=rr;g=gg;b=bb;a=aa;} ~Sun(){} void Show() { for (int light=10;light<241;light+=10){ filledCircleRGBA(screen, x, y, rad+(light/7), r, g, b+(light/2), a-light); } } void Move(int a, int b) { x+=a; y+=b; } }; class Earth { private: int x,y,rad,r,g,b,a; SDL_Surface* screen; public: Earth(SDL_Surface* sc, int xx, int yy, int ra, int rr, int gg, int bb, int aa){screen=sc;x=xx;y=yy;rad=ra;r=rr;g=gg;b=bb;a=aa;} ~Earth(){} void Show() { for (int light=10;light<241;light+=10){ filledCircleRGBA(screen, x, y, rad+(light/7), r, g, b+(light/2), a-(light/2)); } for (double light=0;light<.25;light+=.01){ filledEllipseRGBA(screen, x, y-(rad*1.05), rad*(.60+light), rad*(.1+light), 170+(light*100), 170+(light*100), 170+(light*100), 255-(light*1000)); } } }; int main( int argc, char* args[] ) { //Start SDL SDL_Init( SDL_INIT_EVERYTHING ); SDL_Surface* screen = NULL; screen = SDL_SetVideoMode( 1366, 768, 32, SDL_FULLSCREEN | SDL_SWSURFACE); srand((unsigned)time(NULL)); //Stars for (int x=0;x<1361;x+=25){ for (int y=0;y<766;y+=25){ int Special = rand()%3; if(Special==0||Special==1){ Star star(screen, x+(rand()%30), y+(rand()%30), 0+(rand()%1), 235+rand()%21, 235+rand()%21, 235+rand()%21, 205+rand()%51); star.Show(); } if(Special==2){ Star star(screen, x+(rand()%30), y+(rand()%30), 0+(rand()%2), 235+rand()%21, 235+rand()%21, 235+rand()%21, 205+rand()%51); star.Show(); } } } //Sun Sun sun(screen, 200, 300, 10, 255, 255, 0, 255); sun.Show(); //Earth Earth earth(screen, 700, 400, 100, 0, 80, 255, 255); earth.Show(); SDL_Event event; bool Running=1; bool keysHeld[323]={false}; while (Running) { // Handle input if (SDL_PollEvent(&event)) { if (event.type == SDL_QUIT) { Running = false; } if (event.type == SDL_KEYDOWN) { keysHeld[event.key.keysym.sym] = true; } if (event.type == SDL_KEYUP) { keysHeld[event.key.keysym.sym] = false; } } if ( keysHeld[SDLK_ESCAPE] ) { Running = false; } if ( keysHeld[SDLK_LEFT] ) { } if ( keysHeld[SDLK_RIGHT] ) { SDL_FillRect(screen, NULL, SDL_MapRGB(screen->format, 0, 0, 0)); sun.Move(4,0); sun.Show(); } if ( keysHeld[SDLK_UP] ) { } if (keysHeld[SDLK_DOWN]) { } SDL_Flip(screen); } //Quit SDL SDL_Quit(); return 0; } </code></pre>

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