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## collision detection

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### #1phil67rpg  Members

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Posted 02 December 2012 - 05:08 PM

I am using the following code to implement collision detection between a ball and bricks in a breakout game. My problem is that when I run the program the ball instantly vanishes from the screen. I have been working on this problem for quite some time. I have also been doing a lot of studying on c++ and collision detection.
[code}
void brick_collision()
{
if(x>3.0f && x<5.0f)
{
brick=3.0f;
bricks[3][5]=false;
}

else if(x>1.0f && x<3.0f)
{
brick=1.0f;
bricks[3][4]=false;
}

else if(x>-1.0f && x<1.0f)
{
brick=-1.0f;
bricks[3][3]=false;
}

else if(x>-3.0f && x<-1.0f)
{
brick=-3.0f;
bricks[3][2]=false;
}

else if(x>-5.0f && x<-3.0f)
{
brick=-5.0f;
bricks[3][1]=false;
}

SPRITE object3;
SPRITE object4;

object3.x=x;
object3.y=y;
object3.width=0.1f;
object3.height=0.1f;

object4.x=brick;
object4.y=3.5f;
object4.width=2.0f;
object4.height=1.0f;

if(Sprite_Collide(&object3,&object4)==1)
{
xstep=-xstep;
ystep=-ystep;
}
}
[/code]

### #2BaneTrapper  Members

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Posted 03 December 2012 - 02:55 AM

Am gonna provide rectangle on rectangle collision
//X = starting position X
//Y = starting position Y
//W = Width of the rectangle
//H = Height of the rectangle
rec1;//x y w h
rec2;//x y w h
//The way we gonna check collision is
//From left
//From right
//From top
//From bottom
if(rec1.x + rec1.w > rec2.x &amp;&amp;
rec1.x < rec2.x + rec2.w &amp;&amp;
rec1.y + rec1.h  > rec2.y &amp;&amp;
rec1.y < rec2.y + rec2.w )


EDIT::
I have noticed there is a tag for OpenGL? your checking collision in 3D?

Edited by BaneTrapper, 03 December 2012 - 03:34 AM.

### #3phil67rpg  Members

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Posted 03 December 2012 - 04:06 PM

actually I am working in 2d for now

### #4Khatharr  Members

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Posted 03 December 2012 - 07:20 PM

Hi, Phil.

Edit: Okay, I can see you tried, so I'll help you out some.
• Hit edit on your first post there.
• Delete all the code.
• Copy the code (with formatting) from the original file.
• In the edit window, place the keyboard cursor where the code you deleted used to be.
• At the top of the edit window there are two rows of buttons. Press the red button at the end of the second row:
• Select your language from the drop-down list.
• Past your code into the open space.
• Click 'OK'.
• Click 'Save Changes'.

Typically I use something like the following for rect vs rect:
[source lang="cpp"]//using Microsoft RECT (left, top, right, bottom)bool rectCollideTest(RECT& thisRect, RECT& thatRect) { if(thisRect.left > thatRect.right) {return false;} if(thisRect.right < thatRect.left) {return false;} if(thisRect.top > thatRect.bottom) {return false;} if(thisRect.bottom < thatRect.top) {return false;} return true;}[/source]

This can also be accelerated slightly if you know which exclusion is most likely and move it to the top. That's not something to worry about unless you're doing more collisions than you should though.

Edited by Khatharr, 03 December 2012 - 07:46 PM.

void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #5phil67rpg  Members

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Posted 03 December 2012 - 07:42 PM

sorry about code posting I will be more careful in the future.

### #6Khatharr  Members

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Posted 03 December 2012 - 07:49 PM

The [ code ] tags aren't working correctly anyway, so make sure to use the button.
void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #7phil67rpg  Members

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Posted 03 December 2012 - 08:23 PM

I have one more question, how would one turn off a brick after hitting it with a ball?

### #8Khatharr  Members

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Posted 03 December 2012 - 08:32 PM

That would probably have something to do with whatever it means for a brick to be 'on' or 'off' in your code.
void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #9phil67rpg  Members

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Posted 03 December 2012 - 08:36 PM

[source lang="cpp"]void check_collision(){ if(x>=3.0f && x<=5.0f && y>=3.5f && y<=4.0f) { bricks[3][5]=false; glRectf(3.0f,4.0f,5.0f,3.5f); ystep=-ystep; }well here is the code I am using so far. if(x>=1.0f && x<=3.0f && y>=3.5f && y<=4.0f) { bricks[3][4]=false; glRectf(1.0f,4.0f,3.0f,3.5f); ystep=-ystep; } if(x>=-1.0f && x<=1.0f && y>=3.5f && y<=4.0f) { bricks[3][3]=false; glRectf(-1.0f,4.0f,1.0f,3.5f); ystep=-ystep; } if(x>=-3.0f && x<=-1.0f && y>=3.5f && y<=4.0f) { bricks[3][2]=false; glRectf(-3.0f,4.0f,-1.0f,3.5f); ystep=-ystep; } if(x>=-5.0f && x<=-3.0f && y>=3.5f && y<=4.0f) { bricks[3][1]=false; glRectf(-5.0f,4.0f,-3.0f,3.5f); ystep=-ystep; }}[/source]

### #10phil67rpg  Members

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Posted 03 December 2012 - 08:37 PM

well I tried using the code button, sorry maybe the code html works.

### #11Khatharr  Members

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Posted 03 December 2012 - 09:02 PM

The 'code' button actually uses 'source' tags to wrap your code.

Looking over what you posted, I still don't know what's representing a brick in your code.

Looking at your first post it seems like you're just using sprites and treating them like objects. If you want bricks that do things then you should make a class for bricks that encapsulates their behavior.

Separate your drawing from your logic: Do the logic for the frame and then draw the result.

Edited by Khatharr, 03 December 2012 - 09:02 PM.

void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #12phil67rpg  Members

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Posted 03 December 2012 - 09:20 PM

ok thanks for all the help, actually the hard coded numbers represents the bricks.

### #13Khatharr  Members

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Posted 03 December 2012 - 09:29 PM

So the bool array there represents a grid of bricks?

What do the true/false values indicate?
void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #14phil67rpg  Members

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Posted 03 December 2012 - 09:35 PM

yes, the true/false values indicate that the ball hits one of the bricks.

### #15Khatharr  Members

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Posted 03 December 2012 - 10:39 PM

So if you make that an array of objects or structs then they can have more than one property (was it hit, is it alive, etc).
void hurrrrrrrr() {__asm sub [ebp+4],5;}

There are ten kinds of people in this world: those who understand binary and those who don't.

### #16phil67rpg  Members

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Posted 04 December 2012 - 08:56 PM

ok I will do more research, any other ideas would be helpful

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