# Make two objects interacting with each other

Hello everyone!!

i’m new in this of programming but i am trying to learn by making this sort of codes. I would like the ball and the wall1 interact each other making the ball bounce on the brick.

``````var wall1, wall2;
var ball;

function keyPressed(){
if(keyCode === UP_ARROW){ wall1.y = wall1.y - 80;}
if(keyCode === DOWN_ARROW){
wall1.y = wall1.y + 80;
}
}

function setup() {
createCanvas(650, 500);

wall1 = new Wall(20, 20, 20, 120);
wall2 = new Wall(width - 40, 	20, 20, 120);
ball = new Ball(width/2, height/2, 20);
}

function draw() {
background(0);

let aSq = wall1.b * ball.h;
let aCr = PI * ball.r * ball.r;

let d = dist(ball.x, wall1.x, ball.r, wall1.x/2);

if(d < ball.r + wall1.x/2){
Ball.xspeed = Ball.xspeed * -1;
Ball.yspeed = Ball.yspeed * -1;
}

ball.moveBall();
ball.ball();

//wall1.moveSquare();
wall1.showSquare();

wall2.moveSquare();
wall2.showSquare();
}

class Ball{

constructor(x, y, r){
this.x = x;
this.y = y;
this.r = r;
this.xspeed = random(5, 10);
this.yspeed = random(5, 10);
}

ball(){
stroke(255);
strokeWeight(4);
noFill();
ellipse(this.x, this.y, this.r * 2);
}

moveBall(){
if(this.x >= width || this.x <= 0){
this.xspeed = this.xspeed * -1;
}
this.x = this.x + this.xspeed;

if(this.y >= height || this.y <= 0){
this.yspeed = this.yspeed * -1;
}
this.y = this.y + this.yspeed * -1;
}

}

class Wall{
constructor(x, y, b, h){
this.x = x;
this.y = y;
this.b = b;
this.h = h;
this.yspeed = random(5, 8);
}

showSquare(){

rect(this.x, this.y, this.b, this.h);
}

moveSquare(){
if(this.y >= height-this.h || this.y <= 0){
this.yspeed = this.yspeed * -1;
}
this.y = this.y + this.yspeed;
}

}
``````
1 Like

https://editor.p5js.org/julian2/sketches/SJ3E2QdFX

I’ve tried to make ‘minimal changes’ in the sense that you’ll hopefully recognize how I changed your code. I only introduced a new concept of `paddles` (which is only an array of instances of your `wall` class).

I moved the ‘boundary collision’ code into its own function & created a similar function to do ‘paddle/wall collision checking’, and I’m only doing what you could call a ‘simple collision’ between a box & a single point (the center of the circle). for determining the angle the ball will bounce back in (the ball’s yspeed), i decided to go with the 'distance between the ball and the center of the paddle!

Hopefully the code changes help! If you want to do some more ‘true to life’ collision checking between the ball and the paddles, have a look at http://jeffreythompson.org/collision-detection/circle-rect.php

1 Like

thanks a lot julian2. i am trying to understand a piece of code, may you explain it to me please?

this.xspeed = this.xspeed * -1;
}
}

oh yeah, that code definitively isn’t the best, but I’ll try my best to explain it!

`for (let paddle of paddles) {`
`if (this.x >= paddle.x && this.x <= (paddle.x + paddle.b) && this.y >= paddle.y && this.y <= (paddle.y + paddle.h)) {`
`this.xspeed = this.xspeed * -1;`
`this.yspeed = (this.y - (paddle.y + paddle.h / 2)) / 10;`
and set the y-speed to the ‘y difference’ of the ball and the center of the paddle (hence `paddle.y + paddle.h / 2`). The 10 is a magic number that ‘felt right’ since the ‘pixel distance’ given by the y-difference calculation was a bit too much, so I wanted to scale that down a bit.