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The ball starts off going downward-right and then bounces back the way it came. When it goes up and hits the left wall it again goes back the way it came, back and forth....not sure what is wrong here...

//Ball moves, if reaches wall, bounces off
iBallX += iBallSpeed;
iBallY += iBallSpeed;

if ( iBallX < 0)
{
iBallX += iBallWidth;
iBallSpeed *= -1;
}

else if( iBallX > 1002 - iBallWidth)
{
iBallX -= iBallWidth;
iBallSpeed *= -1;
}

else if( iBallY < 0)
{
iBallY += iBallHeight;
iBallSpeed *= -1;
}

else if( iBallY > 750 - iBallHeight)
{
iBallY -= iBallHeight;
iBallSpeed *= -1;
}

Hi, are you using the DarkGDK as you may get more help from that board. Your problem could be you are using the one variable for both x and y increase and decrease. Try using two variables one for the x increase and decrease and one for the y increase and decrease.

Here is a code snippit that works in DBPro and you should be able to make sense of it.


Hope this helps

I think thats exactly it Hodgey - iBallSpeed, you need to have seperate X and Y, like fBallSpeedX and fBallSpeedY. The speed variables should probably be floats too.

That basic principle looks right enough though, decrement Y speed, if theres a collision then invert the speed. I'm not sure that decrementing the width and height from the position when theres a collision is the best method. I would suggest that you work out the zone left, right, top and bottom, and include the ball size in that - then set the coordinates to limit, rather than detract...

if ( iBallX > 1000 )
{
iBallX = 1000;
if ( iBallSpeedX > 0 ) iBallSpeedX *= -1;
}

if ( iBallX < -1000 )
{
iBallX = -1000;
if ( iBallSpeedX < 0 ) iBallSpeedX *= -1;
}

Something like that maybe.

Nice, that was exactly it. Just added a seperate variable for the speed and vuala! Thank you both for your responses, and I will follow up on other posts under Dark GDK.