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phil67rpg

collision detection

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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;
}
}

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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

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Hi, Phil. rolleyes.gif

Edit: Okay, I can see you tried, so I'll help you out some.

  1. Hit edit on your first post there.
  2. Delete all the code.
  3. Copy the code (with formatting) from the original file.
  4. In the edit window, place the keyboard cursor where the code you deleted used to be.
  5. At the top of the edit window there are two rows of buttons. Press the red button at the end of the second row:
    srcbutt.png
  6. Select your language from the drop-down list.
  7. Past your code into the open space.
  8. Click 'OK'.
  9. 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

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[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]

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