Forums → Programming Forum → The Open Source Coding Challenge #1 - "Pong!" - Discussion

I can get you somewhere to host if you need it. The best way to get more developers is going to be by publicity. Maybe some nice prizes will boost their willingness.

@dank

Do you think you could pull some strings for a merit for the winner?

Thx!

Depends on if there are a decent number of submissions.

Hey everyone!

thought I'd show my progress so far, but this time without the source code, in the interests of healthy competition. Don't worry, come the deadline, all will be revealed!

So now I have the ball bouncing around. Check it out here:

http://awoogamuffinagpc.blogspot.com/

I'm having a lot of trouble with hitTest

How are you guys doing so far?

I'm having a lot of trouble with hitTest

You don't want to use hitTest

The problem is that sometimes the ball will be moving faster than the width of your paddles. So on one frame the ball is to the left of the paddle, but on the next frame it is on the right of the paddle. This means no collision is detected.

You need to do a sweep test. That is, you check the position of the ball before and after moving, to see if it went through the paddle during the frame. It can be a bit tricky. In the interests of keeping this fun, shall I put up some code to help with collision detection? Or should I wait until submission time?

http://www.howstuffworks.com/question435.htm

I posted this for the people that don't know how to do open sourcing.

Could anyone provide an example or a link? I found a lot of hitTest == evil on Google, but none giving an alternative for it

Ok guys, I've got the collision more or less working. it's a bit messy, but at least it works...

I'm using my Vector2D class (you can see it on my blog here) to define the velocity of both the ball and the paddles. This is the function for detecting collision between the ball and a paddle:

public function checkPaddleCollision(paddle:Paddle)
{
var hitHorizontal:Boolean = false;
var hitVertical:Boolean = false;
var fromHorizontal:Boolean = false;
var fromVertical:Boolean = false;
//trace("collision"
//calculate the previous positions of ball and paddle
var paddlePrevX:Number = paddle.x - paddle.velocity.x;
var paddlePrevY:Number = paddle.y - paddle.velocity.y;

var relativeVelocity:Vector2D = new Vector2D();

relativeVelocity.x = x - prevX - paddle.velocity.x;
relativeVelocity.y = y - prevY - paddle.velocity.y;

//SWEEP TESTS:

//check horizontal
if(relativeVelocity.x < 0)
{
//ball coming from right, so check with right hand side of paddle
if(prevX - ballRadius >= paddlePrevX + paddle.paddleWidth && x - ballRadius <= paddle.x + paddle.paddleWidth)
{
hitHorizontal = true;
fromHorizontal = true;
}
}

if(relativeVelocity.x > 0)
{
//ball coming from left, so check with right hand side of paddle
if(prevX + ballRadius <= paddlePrevX && x + ballRadius >= paddle.x)
{
hitHorizontal = true;
fromHorizontal = true;
}
}

//check vertical
if(relativeVelocity.y < 0)
{
//ball coming from below, so check with bottom of paddle
if(prevY - ballRadius >= paddlePrevY + paddle.paddleHeight && y - ballRadius <= paddle.y + paddle.paddleHeight)
{
hitVertical = true;
fromVertical = true;
}
}

if(relativeVelocity.y > 0)
{
//ball coming from above, so check with top of paddle
if(prevY + ballRadius <= paddlePrevY && y + ballRadius >= paddle.y)
{
hitVertical = true;
fromVertical = true;
}
}

//BASIC TESTS:
if(x - ballRadius <= paddle.x + paddle.paddleWidth && x + ballRadius >= paddle.x) hitHorizontal = true;
if(y - ballRadius <= paddle.y + paddle.paddleHeight && y + ballRadius >= paddle.y) hitVertical = true;

if(hitHorizontal && hitVertical) //collision has occurred
{
if (fromHorizontal)
{
relativeVelocity.x < 0 ? x = paddle.x + paddle.paddleWidth + ballRadius : x = paddle.x - ballRadius;
velocity.x *= -1;
if(Math.abs(velocity.x) < Math.abs(paddle.velocity.x)) velocity.x = paddle.velocity.x * 1.4;
else velocity.x += paddle.velocity.x/8;
velocity.y += paddle.velocity.y/((Math.random() + 1) * 3);
}
if (fromVertical)
{
relativeVelocity.y < 0 ? y = paddle.y + paddle.paddleHeight + ballRadius : y = paddle.y - ballRadius;
velocity.y *= -1;
if(Math.abs(velocity.y) < Math.abs(paddle.velocity.y)) velocity.y = paddle.velocity.y * 1.4;
else velocity.y += paddle.velocity.y/8;
velocity.x += paddle.velocity.x/((Math.random() + 1) * 3);
}
}
}

Sorry, it isn't commented much yet - It will be fully commented soon

I'll be happy to answer any questions or queries you have...

Just thinking, it seems a bit slow this week. How many people will have submissions done by Friday?

Anyone want to extend the competition one more week, perhaps making it a monthly contest instead?

I think I'll be finished by Friday, but if people want more time that's fine - It would give me time to try to write a computer AI for the game...

Maybe we should submit with whatever we have, let's just take points out for being incomplete

If Awoogamuffin is the only one that has something done so far, I think one more week might be good.

Are there any others that are planning on submitting anything?