int - I need help slowing down a ball in SDL -
i making "breakout" clone , right ball moving fast. slow down tried convert variables floats , use decimals, ball didn't move @ all.
help me figure out how slow down ball.
//the headers #include "sdl/sdl.h" #include "sdl/sdl_image.h" #include <iostream> #include <string> #include <vector> #include <cmath> #include <stdlib.h> #include <ctime> //the screen attributes const int screen_width = 1008; const int screen_height = 720; const int screen_bpp = 32; const int ball_x = 500; const int ball_y = 600; uint32 white; //the surfaces sdl_surface *mainscreen = null; sdl_surface *difficultyscreen = null; sdl_surface *screen = null; //the event structure sdl_event event; //rects sdl_rect paddle; sdl_rect ball; sdl_rect block1; sdl_rect block2; sdl_rect block3; sdl_rect block4; sdl_rect block5; sdl_rect block6; sdl_rect block7; sdl_rect block8; sdl_rect block9; sdl_rect block10; sdl_rect block11; sdl_rect block12; sdl_rect block13; sdl_rect block14; sdl_rect block15; sdl_rect block16; sdl_rect block17; sdl_rect block18; sdl_rect block19; sdl_rect block20; sdl_rect block21; sdl_rect block22; sdl_rect block23; sdl_rect block24; sdl_rect block25; sdl_rect block26; int xvel, yvel; bool pointinrect(int x, int y, sdl_rect rec) { if (x > rec.x && y > rec.y && x < rec.x + rec.w && y < rec.y + rec.h) { return true; } return false; } bool checkcollision(sdl_rect r1, sdl_rect r2) { if (pointinrect(r1.x, r1.y, r2) == true || pointinrect(r1.x + r1.w, r1.y, r2) == true || pointinrect(r1.x, r1.y + r1.h, r2) == true || pointinrect(r1.x + r1.w, r1.y + r1.h, r2) == true) { return true; } return false; } void resetball() { ball.x = ball_x; ball.y = ball_y; xvel = 1; yvel = 1; } void loadgame() { paddle.x = 425; paddle.y = 650; paddle.h = 20; paddle.w = 150; ball.x = ball_x; ball.y = ball_y; ball.h = 15; ball.w = 15; block1.x = 58; block1.y = 28; block1.h = 15; block1.w = 100; block2.x = 216; block2.y = 28; block2.h = 15; block2.w = 100; block3.x = 374; block3.y = 28; block3.h = 15; block3.w = 100; block4.x = 533; block4.y = 28; block4.h = 15; block4.w = 100; block5.x = 691; block5.y = 28; block5.h = 15; block5.w = 100; block6.x = 849; block6.y = 28; block6.h = 15; block6.w = 100; block7.x = 84; block7.y = 71; block7.h = 15; block7.w = 100; block8.x = 269; block8.y = 71; block8.h = 15; block8.w = 100; block9.x = 453; block9.y = 71; block9.h = 15; block9.w = 100; block10.x = 638; block10.y = 71; block10.h = 15; block10.w = 100; block11.x = 822; block11.y = 71; block11.h = 15; block11.w = 100; block12.x = 23; block12.y = 114; block12.h = 15; block12.w = 100; block13.x = 146; block13.y = 114; block13.h = 15; block13.w = 100; block14.x = 269; block14.y = 114; block14.h = 15; block14.w = 100; block15.x = 392; block15.y = 114; block15.h = 15; block15.w = 100; block16.x = 516; block16.y = 114; block16.h = 15; block16.w = 100; block17.x = 639; block17.y = 114; block17.h = 15; block17.w = 100; block18.x = 762; block18.y = 114; block18.h = 15; block18.w = 100; block19.x = 885; block19.y = 114; block19.h = 15; block19.w = 100; block20.x = 88; block20.y = 157; block20.h = 15; block20.w = 100; block21.x = 820; block21.y = 157; block21.h = 15; block21.w = 100; block22.x = 138; block22.y = 200; block22.h = 15; block22.w = 100; block23.x = 296; block23.y = 200; block23.h = 15; block23.w = 100; block24.x = 454; block24.y = 200; block24.h = 15; block24.w = 100; block25.x = 612; block25.y = 200; block25.h = 15; block25.w = 100; block26.x = 770; block26.y = 200; block26.h = 15; block26.w = 100; white = sdl_maprgb(screen->format, 255, 255, 255); srand(time(null)); resetball(); } void logic() { sdl_event occur; sdl_pollevent(&occur); uint8 *keystates = sdl_getkeystate(null); if (keystates[sdlk_left]) { paddle.x -= 1; } if (keystates[sdlk_right]) { paddle.x += 1; } if (paddle.x < 1) { paddle.x = 1; } if (paddle.x + paddle.w > 1007) { paddle.x = 1007 - paddle.w; } //for ball movement ball.x += xvel; ball.y += yvel; //change direction of ball if ball hits walls if (ball.y < 1) { yvel = -yvel; } if (ball.y + ball.h > 1007) { yvel = -yvel; } if (ball.x < 1) { xvel = -xvel; } if (ball.x + ball.w > 1007) { xvel = -xvel; } //change direction of ball if ball hits paddle if (checkcollision(ball, paddle) == true) { yvel = -yvel; } //change direction of ball if ball hits blocks if (checkcollision(ball, block1) == true) { yvel = -yvel; block1.x = -200; block1.y = -200; } if (checkcollision(ball, block2) == true) { yvel = -yvel; block2.x = -200; block2.y = -200; } if (checkcollision(ball, block3) == true) { yvel = -yvel; block3.x = -200; block3.y = -200; } if (checkcollision(ball, block4) == true) { yvel = -yvel; block4.x = -200; block4.y = -200; } if (checkcollision(ball, block5) == true) { yvel = -yvel; block5.x = -200; block5.y = -200; } if (checkcollision(ball, block6) == true) { yvel = -yvel; block6.x = -200; block6.y = -200; } if (checkcollision(ball, block7) == true) { yvel = -yvel; block7.x = -200; block7.y = -200; } if (checkcollision(ball, block8) == true) { yvel = -yvel; block8.x = -200; block8.y = -200; } if (checkcollision(ball, block9) == true) { yvel = -yvel; block9.x = -200; block9.y = -200; } if (checkcollision(ball, block10) == true) { yvel = -yvel; block10.x = -200; block10.y = -200; } if (checkcollision(ball, block11) == true) { yvel = -yvel; block11.x = -200; block11.y = -200; } if (checkcollision(ball, block12) == true) { yvel = -yvel; block12.x = -200; block12.y = -200; } if (checkcollision(ball, block13) == true) { yvel = -yvel; block13.x = -200; block13.y = -200; } if (checkcollision(ball, block14) == true) { yvel = -yvel; block14.x = -200; block14.y = -200; } if (checkcollision(ball, block15) == true) { yvel = -yvel; block15.x = -200; block15.y = -200; } if (checkcollision(ball, block16) == true) { yvel = -yvel; block16.x = -200; block16.y = -200; } if (checkcollision(ball, block17) == true) { yvel = -yvel; block17.x = -200; block17.y = -200; } if (checkcollision(ball, block18) == true) { yvel = -yvel; block18.x = -200; block18.y = -200; } if (checkcollision(ball, block19) == true) { yvel = -yvel; block19.x = -200; block19.y = -200; } if (checkcollision(ball, block20) == true) { yvel = -yvel; block20.x = -200; block20.y = -200; } if (checkcollision(ball, block21) == true) { yvel = -yvel; block21.x = -200; block21.y = -200; } if (checkcollision(ball, block22) == true) { yvel = -yvel; block22.x = -200; block22.y = -200; } if (checkcollision(ball, block23) == true) { yvel = -yvel; block23.x = -200; block23.y = -200; } if (checkcollision(ball, block24) == true) { yvel = -yvel; block24.x = -200; block24.y = -200; } if (checkcollision(ball, block25) == true) { yvel = -yvel; block25.x = -200; block25.y = -200; } if (checkcollision(ball, block26) == true) { yvel = -yvel; block26.x = -200; block26.y = -200; } } //function load image sdl_surface *load_image( std::string filename ) { //temporary storage image that's loaded sdl_surface* loadedimage = null; //the optimized image used sdl_surface* optimizedimage = null; loadedimage = sdl_loadbmp(filename.c_str()); //if nothing went wrong in loading image if(loadedimage != null) { //create optimized image optimizedimage = sdl_displayformat(loadedimage); //free old surface sdl_freesurface(loadedimage); } //return optimized image return optimizedimage; } //function apply picture screen 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); } //function start sdl bool init() { //initialize sdl subsystems if( sdl_init( sdl_init_everything ) == -1 ) { return false; } //set screen screen = sdl_setvideomode( screen_width, screen_height, screen_bpp, sdl_swsurface ); //if there error in setting screen if( screen == null ) { return false; } //name window sdl_wm_setcaption( "block breaker", null ); //if initialized fine return true; } //function load files bool load_files() { //load image mainscreen = load_image( "menu.bmp" ); difficultyscreen = load_image( "speed menu.bmp" ); return true; } //function stop sdl void clean_up() { sdl_freesurface(mainscreen); sdl_freesurface(difficultyscreen); sdl_freesurface(screen); //quit sdl sdl_quit(); } int main( int argc, char* args[] ) { //variables bool running = true; bool menu = true; bool difficulty = false; bool mediumgame = false; bool hardgame = false; bool quit = false; //initialize if ( init() == false ) { return 1; } //quit function if (quit == true) { sdl_quit(); } //load files if ( load_files() == false ) { return 1; } loadgame(); //while user hasn't quit while (quit == false) { //menu screen if (menu==true) { //apply screen apply_surface(0,0,mainscreen,screen); //loop handle input user while(sdl_pollevent(&event)) { if (event.type==sdl_mousebuttonup) { if (event.button.button == sdl_button_left) { int x = event.button.x; int y = event.button.y; //button difficulty screen if ((x>370)&&(x<660)&&(y>265)&&(y<370)) { menu = false; difficulty = true; sdl_flip(screen); } if ((x>374)&&(x<660)&&(y>390)&&(y<500)) { menu = false; quit = true; sdl_flip(screen); } } sdl_flip(screen); } else if (event.type==sdl_quit) { quit = true; } } sdl_flip(screen); } //difficulty screen else if (difficulty==true) { //apply surface apply_surface(0,0,difficultyscreen,screen); sdl_flip(screen); while (sdl_pollevent(&event)) { if (event.type==sdl_mousebuttonup) { if (event.button.button == sdl_button_left) { int x = event.button.x; int y = event.button.y; //button medium game screen if ((x>360)&&(x<660)&&(y>370)&&(y<465)) { difficulty = false; mediumgame = true; sdl_flip(screen); } //button hard game screen if ((x>420)&&(x<610)&&(y>490)&&(y<575)) { difficulty = false; hardgame = true; sdl_flip(screen); } } sdl_flip(screen); } else if (event.type==sdl_quit) { quit = true; } } } //medium game screen else if (mediumgame == true) { //fill color sdl_fillrect(screen, &screen->clip_rect, sdl_maprgb( screen->format, 0x68, 0x68, 0x68 )); //logic game logic(); //place paddle sdl_fillrect(screen, &paddle, white); //place ball sdl_fillrect(screen, &ball, white); //place blocks sdl_fillrect(screen, &block1, white); sdl_fillrect(screen, &block2, white); sdl_fillrect(screen, &block3, white); sdl_fillrect(screen, &block4, white); sdl_fillrect(screen, &block5, white); sdl_fillrect(screen, &block6, white); sdl_fillrect(screen, &block7, white); sdl_fillrect(screen, &block8, white); sdl_fillrect(screen, &block9, white); sdl_fillrect(screen, &block10, white); sdl_fillrect(screen, &block11, white); sdl_fillrect(screen, &block12, white); sdl_fillrect(screen, &block13, white); sdl_fillrect(screen, &block14, white); sdl_fillrect(screen, &block15, white); sdl_fillrect(screen, &block16, white); sdl_fillrect(screen, &block17, white); sdl_fillrect(screen, &block18, white); sdl_fillrect(screen, &block19, white); sdl_fillrect(screen, &block20, white); sdl_fillrect(screen, &block21, white); sdl_fillrect(screen, &block22, white); sdl_fillrect(screen, &block23, white); sdl_fillrect(screen, &block24, white); sdl_fillrect(screen, &block25, white); sdl_fillrect(screen, &block26, white); //flip screen sdl_flip(screen); } //hard game screen else if (hardgame == true) { //fill color sdl_fillrect(screen, &screen->clip_rect, sdl_maprgb( screen->format, 0x68, 0x68, 0x68 )); //logic game logic(); //place paddle sdl_fillrect(screen, &paddle, white); //place ball sdl_fillrect(screen, &ball, white); //place blocks sdl_fillrect(screen, &block1, white); sdl_fillrect(screen, &block2, white); sdl_fillrect(screen, &block3, white); sdl_fillrect(screen, &block4, white); sdl_fillrect(screen, &block5, white); sdl_fillrect(screen, &block6, white); sdl_fillrect(screen, &block7, white); sdl_fillrect(screen, &block8, white); sdl_fillrect(screen, &block9, white); sdl_fillrect(screen, &block10, white); sdl_fillrect(screen, &block11, white); sdl_fillrect(screen, &block12, white); sdl_fillrect(screen, &block13, white); sdl_fillrect(screen, &block14, white); sdl_fillrect(screen, &block15, white); sdl_fillrect(screen, &block16, white); sdl_fillrect(screen, &block17, white); sdl_fillrect(screen, &block18, white); sdl_fillrect(screen, &block19, white); sdl_fillrect(screen, &block20, white); sdl_fillrect(screen, &block21, white); sdl_fillrect(screen, &block22, white); sdl_fillrect(screen, &block23, white); sdl_fillrect(screen, &block24, white); sdl_fillrect(screen, &block25, white); sdl_fillrect(screen, &block26, white); //flip screen sdl_flip(screen); } } //clean clean_up(); return 0; }
short answer: use floats ball position.
using floats velocity right thing if think you'll need adjust speed finer precision integer pixel resolution of screen. reason ball didn't move @ when used floating point velocities because not using floating point positions.
here's example:
int x = 4; float velx = 0.05f; x += velx; what value x going have? same value this:
for(int = 0; < 1000; ++i) x += velx; x not changing because can ever integer , decimal value truncated when stored integer. change x float work properly. in case, don't use sdl_rect (which 4 ints) store position of objects. create own class/struct uses floats.
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