circle - circle collision

circle - circle collision

chaseC

Member #8,368

February 2007

Hi, I am making an air hockey game and I need some help with puck to the thing you use to hit the puck collision. The collision isn't the real problem, the problem is that if I move the puck hitting thing to fast it goes through the puck and sends it in the wrong direction. I need some advise???

BAF

Member #2,981

December 2002

What, one account and thread wasn't enough to get people to program your game for you?

BAF.zone | SantaHack!

Ceagon Xylas

Member #5,495

February 2005

Line collision. Begin the line at the puck, end it at the puck's coordinates plus it's velocity. Check to see if that line collides with any of the walls (other lines)

chaseC

Member #8,368

February 2007

What I mean is that if the paddle (I don't know if it is actually called a paddle) moves to fast when it is in the path of the puck, it changes position so many pixels at a time that it moves into the puck and sends it in the wrong direction. Also I am not zavirx, my code doen't look anything like his ->

1#include <allegro.h>
2 
3#define BALL_SPEED_MOD    12
4 
5struct comp{
     float x;
     float y;
     
     float x_speed;
     float y_speed;
     
     int h;
     int w;
     
     int time;
16};
17 
18struct player{
     float x;
     float y;
     
     float x_speed;
     float y_speed;
     
     int h;
     int w;
27};
28 
29comp p2;
30comp puck;
31 
32player p1;
33 
34BITMAP *buffer;
35BITMAP *Player;
36BITMAP *Comp;
37BITMAP *Puck;
38 
39int GameSpeed;
40 
41void SpeedCounter(){
  GameSpeed++;
43} END_OF_FUNCTION(SpeedCounter);
44 
45void SetUp();
46void HandlePuck();
47void Bounce();
48void Bounce2();
49void MovePlayer();
50void DrawStuff();
51 
52void SetUp(){
   
   p1.x = 260;
   p1.y = 240;
   p1.w = 28;
   p1.h = 28;
   
   p2.x = 380;
   p2.y = 240;
   p2.w = 28;
   p2.h = 28;
   
   puck.x = 320;
   puck.y = 140;
   puck.w = 23;
   puck.h = 23;
   puck.y_speed = 0;
   puck.x_speed = -1;
70}
71 
72void HandlePuck(){
   
   Bounce();
   Bounce2();
   
   puck.x += puck.x_speed;
   puck.y += puck.y_speed;
   
   if(puck.y_speed < 0 && puck.y - puck.w <= 60 || puck.y_speed > 0 && puck.y + puck.w >= 420){
      puck.y_speed = -puck.y_speed;
   }if(puck.x_speed < 0 && puck.x - puck.w <= 20 && puck.y < 180 || puck.x_speed < 0 && puck.x - 
   puck.w <= 20 && puck.y + puck.w > 280|| puck.x_speed > 0 && puck.x + puck.w >= 619&& puck.y - 
   puck.w < 180 || puck.x_speed > 0 && puck.x + puck.w >= 619 && puck.y - puck.w > 280){
      puck.x_speed = -puck.x_speed;
   }
   puck.x_speed *= 0.996;
   puck.y_speed *= 0.996;
89}
90 
91void Bounce(){
   
   static int puck_bounce = 0;
   const float dx = p1.x - puck.x;
   const float dy = p1.y - puck.y;
   const float dist = p1.w + puck.w;
97 
   if(((dx * dx) + (dy * dy)) < (dist * dist) && puck_bounce == 0){
          puck.x_speed = -(((p1.x + p1.w) - (puck.x + puck.w))/BALL_SPEED_MOD) + (p1.x_speed/BALL_SPEED_MOD) - (puck.x_speed/BALL_SPEED_MOD);
          puck.y_speed = -(((p1.y + p1.w) - (puck.y + puck.w))/BALL_SPEED_MOD) + (p1.y_speed/BALL_SPEED_MOD) - (puck.y_speed/BALL_SPEED_MOD);
          puck_bounce = 1;
   }
   if(((dx * dx) + (dy * dy)) > (dist * dist)){
          puck_bounce = 0;
   }
106}
107 
108void Bounce2(){
   
   const float dx = p2.x - puck.x;
   const float dy = p2.y - puck.y;
   const float dist = p2.w + puck.w;
113 
   if(((dx * dx) + (dy * dy)) < (dist * dist)){
          puck.x_speed = -(((p2.x + p2.w) - (puck.x + puck.w))/BALL_SPEED_MOD) + p2.x_speed;
          puck.y_speed = -(((p2.y + p2.w) - (puck.y + puck.w))/BALL_SPEED_MOD) + p2.y_speed;
   }
118}
   
120void MovePlayer(){
   
   int mickeyx;
   int mickeyy;
   
   get_mouse_mickeys(&mickeyx, &mickeyy);
   
   if(!(mouse_b & 1) && !(mouse_b & 2)){
                 p1.x_speed = mickeyx/8;
                 p1.y_speed = mickeyy/8;
   }else if(mouse_b & 1){
         p1.y_speed = 0;
         if(mickeyx <= 1 && mickeyx >= -1){
                    p1.x_speed *= 0.99;
         }else{
               p1.x_speed = mickeyx/8;
         }
   }else if(mouse_b & 2){
         p1.x_speed = 0;
         if(mickeyy <= 1 && mickeyy >= -1){
                    p1.y_speed *= 0.99;
         }else{
               p1.y_speed = mickeyy/8;
         }
   }
   p1.x += p1.x_speed;
   p1.y += p1.y_speed;
147}
148 
149void DrawStuff(){
   
   clear_to_color(buffer, makecol(255, 255, 255));
   
   rect( buffer, 20, 60, 619, 420, makecol(255, 0, 0));
   rect( buffer, 0, 180, 20, 280, makecol( 0, 0, 0));
   rect( buffer, 619, 180, 639, 280, makecol(0, 0, 0));
   line( buffer, 320, 60, 320, 420, makecol( 255, 0, 0));
   circle( buffer, 320, 240, 80, makecol(0, 128, 255));
   draw_sprite(buffer, Puck, puck.x - puck.w, puck.y - puck.w);
   draw_sprite(buffer, Comp, p2.x - p2.w, p2.y - p2.h);
   draw_sprite(buffer, Player, p1.x - p1.w, p1.y - p1.h);
   
   draw_sprite(screen, buffer, 0, 0);
163}
164 
165int main(int argc, char *argv[]){
166 
  allegro_init();
  install_timer();
  install_keyboard();
  install_mouse();
  set_color_depth(32);
  set_gfx_mode( GFX_AUTODETECT, 640, 480, 0, 0);
  
  LOCK_FUNCTION(speed_counter);
  LOCK_VARIABLE(GameSpeed);
  install_int_ex(SpeedCounter, BPS_TO_TIMER(90));
  
  set_mouse_range(20, 60, 320, 420);
  set_mouse_speed(32, 32);
  
  buffer = create_bitmap( 640, 480);
  Player = load_bitmap("hockey_paddle.bmp", NULL);
  Comp = load_bitmap("hockey_paddle2.bmp", NULL);
  Puck = load_bitmap("hockey_puck.bmp", NULL);
  set_window_title("Air Hockey");
  
  SetUp();
  while( !key[KEY_ESC]){
         while(GameSpeed > 1){
                         MovePlayer();
                         HandlePuck();
                         GameSpeed--;
         }
         DrawStuff();
  }  
  
  return 0;
198 
199}
200END_OF_MAIN();

Also, I actually know how to add code tags;D

Ceagon Xylas

Member #5,495

February 2005

My suggestion will solve this. Just replace the word 'walls' with 'paddles.'

Andrei Ellman

Member #3,434

April 2003

Are the puck and the paddle both circular? The subject of the post is "circle - circle collision", but in the code you posted the puck has a width and a height which means it can be a rectangle. I'll assume you meant a circle-circle collision.

A circle is the set of points that is at an exact distance (the radius) from the circle centre point. This means that any point who'se closest distance to the centre is is less than the radius is colliding with the circle. For two moving circles, you just need to find if the closest distance between the two line segments (each line segment is from the initial position of the puck to the position of the puck with the distance traveled during the iteration (velocity * length_of_iteration)) is less than the combined radii of the two circles. Don't forget to take into account that if the puck rebounds off a wall, the line-segment is broken.

AE.

--
Don't let the illegitimates turn you into carbon.

zavirax

Member #8,634

May 2007

haha, ill be coming here when mines done because mines just square at the moment...finally, someone with a similar problem.

And yeah your code is much more confusing and i guess advance than mine but mine kinda works so i dont mind because i know what im doing just dont know how to do it.