no-reply@allegro.cc (chaseC) — Fri, 04 May 2007 07:22:04 +0000

Hi, I'm making a breakout clone but I've run into a problem with the collision detection. I'm using an array to store the positions of all the bricks but I don't know how to check to see if the ball has hot them.

Can someone help please?:(

no-reply@allegro.cc (CursedTyrant) — Fri, 04 May 2007 17:47:00 +0000

First answer: attach yer bloody code

You could use simple bounding box collisions.

1 
2struct sball
3{
4  int x, y; //ball's position
5  int r; //ball's radius
6} sball;
7 
8struct sbrick
9{
10  int x, y; //brick's position
11  int w, h; //brick's size
12} sbrick;
13 
14sball ball;
15sbrick brick[32][32]; //assuming it's a 32x32 2D array, change as needed
16 
17//...
18 
19for (int y=0; y<32; y++)
20{
21for (int x=0; x<32; x++)
22{
23  if (ball.y-ball.r<=brick[x][y].y+brick[x][y].h && ball.x+ball.r>brick[x][y].x & ball.x+ball.r<brick[x][y].x+brick[x][y].w) //check the top bound of the ball versus the bottom bound of the brick
24  { allegro_message("Hit!"); }
25  if (ball.x-ball.r<=brick[x][y].x+brick[x][y].w && ball.y-ball.r>brick[x][y].y && ball.y+ball.r<brick[x][y].y) //check the left bound of the ball versus the right bound of the brick
26  { allegro_message("Hit!"); }
27  
28  //... and so on ...
29  
30}
31}

It's not tested, so it may contain mistakes.

1
2	struct sball
3	{
4	int x, y; //ball's position
5	int r; //ball's radius
6	} sball;
7
8	struct sbrick
9	{
10	int x, y; //brick's position
11	int w, h; //brick's size
12	} sbrick;
13
14	sball ball;
15	sbrick brick[32][32]; //assuming it's a 32x32 2D array, change as needed
16
17	//...
18
19	for (int y=0; y<32; y++)
20	{
21	for (int x=0; x<32; x++)
22	{
23	if (ball.y-ball.r<=brick[x][y].y+brick[x][y].h && ball.x+ball.r>brick[x][y].x & ball.x+ball.r<brick[x][y].x+brick[x][y].w) //check the top bound of the ball versus the bottom bound of the brick
24	{ allegro_message("Hit!"); }
25	if (ball.x-ball.r<=brick[x][y].x+brick[x][y].w && ball.y-ball.r>brick[x][y].y && ball.y+ball.r<brick[x][y].y) //check the left bound of the ball versus the right bound of the brick
26	{ allegro_message("Hit!"); }
27
28	//... and so on ...
29
30	}
31	}

Array colision detection