Thread: Pong--paddle collision algorithm help

hello all!

I'm new to the forum, so forgive me if i'm asking too much or if i'm asking something unreasonable. For my APCS class, we were told to make one of three games. I choose the hardest of the three, pong. We were supplied with some basic code as an outline to start off of. Currently, i've created a game of pong were the left and right paddle move properly, but the ball does not bounce off of the right paddle correctly. If i manage to get the ball to the left side, if bounces off the paddle if the paddle is in its course. the ball sticks to the left or right wall if it hits it. it bounces off of the the top and bottom walls as it's supposed to. the code is attached below. There are six classes that i use for this. In the actual "pong" class (not the class "the game") the algorithm for detecting if the ball hits the right paddle is off (like i said before). Can anyone help? Cheers!


the algorithm that needs fixing is as follows:

if(  (ball.getX() <=  rightPaddle.getX() + rightPaddle.getWidth() + Math.abs(ball.getXSpeed()) 
				 && (ball.getY() >= rightPaddle.getY() 
				 && ball.getY() <= rightPaddle.getY() + rightPaddle.getHeight()
				 || ball.getY() + ball.getHeight() >= rightPaddle.getY()
				 && ball.getY() + ball.getHeight()  < rightPaddle.getY() + rightPaddle.getHeight())))
		{
			 System.out.println("hit Right Paddle");
 
		   if(ball.getX() >= rightPaddle.getX() + rightPaddle.getWidth() - Math.abs(ball.getXSpeed()))
		   {
		       ball.setYSpeed(-ball.getYSpeed());
		       //System.out.println("changing y speed");
		   }
		   else
		{
		       ball.setXSpeed(-ball.getXSpeed());
		       //System.out.println("changing x speed");
		       }
		}

Ball.txt
Block.txt
Locatable.txt
paddle.txt
pong.txt
TheGame.txt

Hi norm,

When the right paddle moves in front of the ball (when they have the same y values if i'm not mistaken) the ball stutters back and forth and moves in the same direction up or down, but stutters left and right while the right paddle is in it's direct line of sight. I tried putting prints in, but i couldn't debug it. Also tried flipping the greater than and less than signs and it didn't really help. Any ideas?

Originally Posted by Norm

The print out should help you see why the ball stutters when near the paddle. It should show which of the great number of conditions in the if statement is true when the ball changes direction.

Hi again, just saw the reply. The ball stutters when its y value correlates with the right paddles y value. It isn't a particular y value though, it is for any y value when the two are the same (that's confusing to read---the ball stutters when both the y value for the ball and the paddle are the same, at any location)

print statements are as follows: I just pulled a handful from before the ball intercepts the paddles y intercept, as both y values are the same, and after the y value of the ball are past the paddles y value. It seems that when the y values come between 40 of each other, the ball starts acting up. In the print statement, there is a "hit right paddle" if the first "if" statement which should determine if the paddle actually hits the ball. In this scenario, it prints when their y values are within 40 (if i'm not mistaken)



Ball X 310
Ball Y 310
Right Paddle Y 156
Left Paddle Y 100

Ball X 312
Ball Y 312
Right Paddle Y 164
Left Paddle Y 100

Ball X 314
Ball Y 314
Right Paddle Y 172
Left Paddle Y 100

Ball X 316
Ball Y 316
Right Paddle Y 180
Left Paddle Y 100

Ball X 318
Ball Y 318
Right Paddle Y 188
Left Paddle Y 100

Ball X 320
Ball Y 320
Right Paddle Y 196
Left Paddle Y 100

Ball X 322
Ball Y 322
Right Paddle Y 204
Left Paddle Y 100

Ball X 324
Ball Y 324
Right Paddle Y 212
Left Paddle Y 100

Ball X 326
Ball Y 326
Right Paddle Y 220
Left Paddle Y 100

Ball X 328
Ball Y 328
Right Paddle Y 228
Left Paddle Y 100

Ball X 330
Ball Y 330
Right Paddle Y 236
Left Paddle Y 100

Ball X 332
Ball Y 332
Right Paddle Y 244
Left Paddle Y 100

Ball X 334
Ball Y 334
Right Paddle Y 252
Left Paddle Y 100

Ball X 336
Ball Y 336
Right Paddle Y 260
Left Paddle Y 100

Ball X 338
Ball Y 338
Right Paddle Y 268
Left Paddle Y 100

Ball X 340
Ball Y 340
Right Paddle Y 276
Left Paddle Y 100

Ball X 342
Ball Y 342
Right Paddle Y 284
Left Paddle Y 100

Ball X 344
Ball Y 344
Right Paddle Y 292
Left Paddle Y 100

hit Right Paddle
Ball X 346
Ball Y 346
Right Paddle Y 300
Left Paddle Y 100

hit Right Paddle
Ball X 344
Ball Y 348
Right Paddle Y 308
Left Paddle Y 100

hit Right Paddle
Ball X 346
Ball Y 350
Right Paddle Y 316
Left Paddle Y 100

hit Right Paddle
Ball X 344
Ball Y 352
Right Paddle Y 324
Left Paddle Y 100

hit Right Paddle
Ball X 346
Ball Y 354
Right Paddle Y 332
Left Paddle Y 100

hit Right Paddle
Ball X 344
Ball Y 356
Right Paddle Y 340
Left Paddle Y 100

hit Right Paddle
Ball X 346
Ball Y 358
Right Paddle Y 348
Left Paddle Y 100

hit Right Paddle
Ball X 344
Ball Y 360
Right Paddle Y 356
Left Paddle Y 100

hit Right Paddle
Ball X 346
Ball Y 362
Right Paddle Y 364
Left Paddle Y 100

hit Right Paddle
Ball X 344
Ball Y 364
Right Paddle Y 372
Left Paddle Y 100

Ball X 346
Ball Y 366
Right Paddle Y 380
Left Paddle Y 100

Ball X 348
Ball Y 368
Right Paddle Y 388
Left Paddle Y 100

Ball X 350
Ball Y 370
Right Paddle Y 396
Left Paddle Y 100

Ball X 352
Ball Y 372
Right Paddle Y 404
Left Paddle Y 100

Ball X 354
Ball Y 374
Right Paddle Y 404
Left Paddle Y 100

Ball X 356
Ball Y 376
Right Paddle Y 404
Left Paddle Y 100

Ball X 358
Ball Y 378
Right Paddle Y 404
Left Paddle Y 100

Ball X 360
Ball Y 380
Right Paddle Y 404
Left Paddle Y 100

Ball X 362
Ball Y 382
Right Paddle Y 404
Left Paddle Y 100

Ball X 364
Ball Y 384
Right Paddle Y 404
Left Paddle Y 100

Ball X 366
Ball Y 386
Right Paddle Y 404
Left Paddle Y 100

Ball X 368
Ball Y 388
Right Paddle Y 404
Left Paddle Y 100

Ball X 370
Ball Y 390
Right Paddle Y 404
Left Paddle Y 100

The right and left paddle's x values do not change and are 555, and 0, respectively. There is a print statement when there is a collision-- if you look, there is a print of "hit Right Paddle" in certain circumstances. If it hits the left paddle, there is a print statement "hit Left Paddle". The ball is 10x10 and the paddles are 20x50. Does that help? and why shouldn't i have print statements all the time? I need to know the values either way don't I?

I don't quite follow---what will this tell me?

I already tried the random changes, and of course, that didn't work so i'll try doing the other print statements later