New to Processing help

Programming Questions

thorpedo31

in Programming Questions • 1 years ago

Hello,

I am new to processing and am looking for some help with arrays.
What I had done originally, is make a ball fall from the top of the screen due to gravity. The ball had to appear at a random x position due to gravity. This was for one ball.
I did this fine.
My next task was to change my code so that you have an array of 100 balls which when you press the mouse on the output window a ball falls from the x position where you click the mouse. The y position will always be the same, since it is falling from the top of the window. The array of 100 balls is so that every time you click the mouse, a ball falls.

So I changed my code to make an array of 100 balls. The array was just going to be called ball1 since that's what the one ball was called in my original code.

I am new to arrays and don't fully understand how to use them in code. So I am trying to learn. If someone could please help me with me code and how to get this to work and explain it if you can, that would be great.

Thanks in advance.

final float acceleration = 0.98; //acceleration due to gravity.
int numBalls = 0; // global var to keep track of how many balls are on the screen.

//initializing the balls to move around.
Ball ball1[100];
//Definition of what a "Ball" actually is.
class Ball {
float r;
float x,y;
float vx,vy;
float direction;

Ball(float p1, float p2, float p3, float p4, float p5, float p6){ // constructor
    r = p1;
    x = p2;
    y = p3;
    vx = p4;
    vy = p5;
    direction = p6;
}
}

void setup(){
size(400,400);
smooth();

}

void draw(){
background(255,255,255);
numBalls++;
if (numBalls >= ball1.length){
   numBalls = 0;} //start array over
//Draw and move the balls
for (int i=0;i<numBalls;i++){
    ball1[i].drawBall();
    ball1[i].moveBall();
    }
}

void mousePressed(){
ball1[numBalls] = new Ball (25, mouseX, 0, 0, 0, -1);

}

void drawBall(Ball aBall){
fill(33,232,23);
ellipse(aBall.x, aBall.y, aBall.r, aBall.r);
}

void moveBall(Ball aBall){
aBall.vy += acceleration;
aBall.y += aBall.vy;
if(aBall.y > height - 2.5){
    aBall.vy *= aBall.direction;}
}

Replies(2)

kritzikra..

Re: New to Processing help

1 years ago

hey!

because it's late you only get a semi-complete answer.

you can find the corrected version of your code here:

http://pastebin.com/JsAPwPHb

here's a quick intro to arrays i just made up:

think about a book.

you don't give each page an individual name.

it's just a lot of pages and each page has a number.

to get any page in any book you need to know the name

of the book and the number of the page.

in programming this is the name of the variable and the

index of the element.

in programming it's very common that you have

to deal with large quantities of things often and

you'll use arrays to store those.

well, this is the abstract view; technical notes are below;

i did remove all parts of your program that were correct.

[.....]
//initializing the balls to move around.
Ball ball1[] = new Ball[100];

you had Ball ball1[100];

which works in other programing languages,

but not in processing.

the left side Ball ball1[] means that you create a new

array variable with the name ball1, and it will hold Ball things as elements.

the right side actually creates the array and says it will have space

for 100 balls.

the equals sign in between is what brings the variable ball1 and the empty space

for the 100 balls together.

note: no balls have been created at this point, just an "empty space" where

you can put up to 100 Ball elements (and nothing else!)

[...]
void setup(){
size(400,400);
smooth();
// create all the balls, this is required!
for( int i = 0; i < ball1.length; i++ ){
ball1[i] = new Ball( 0, 0, 0, 0, 0, 0 );
}

this empty space i was talking about above is actually kind of

annoying and causes all sorts of trouble,

so we create "stupid" balls. they don't move,

they don't show on the screen, but it's better

than nothing :)

[...]
void draw(){
background(255,255,255);
//Draw and move the balls
for (int i=0;i<numBalls;i++){
drawBall( ball1[i] );
moveBall( ball1[i] );

you had ball1[i].draw();

well, i don't want to get into details here,

but the method drawBall() is written outside of

the Ball class and also you wrote it in a way so

that a ball object needs to be passed into it.

this is what we do here.

ball[i] gives us the ball with number i ,

and we pass that ball into the drawBall() and moveBall() functions.

void mousePressed(){
ball1[numBalls] = new Ball (25, mouseX, 0, 0, 0, -1);
numBalls++;
if (numBalls >= ball1.length){
numBalls = 0;} //start array over
}

i am too tired now,

but you can see that i moved this block from your

draw() function down here.

you'll need to figure out by yourself why it wasn't of use up there :)

hope my semi-complete answer helps,

best,

hansi.

thorpedo31

Re: New to Processing help

1 years ago

Thank you so much! I appreciate you taking the time to write that! :) It makes sense! If you or someone else gets a chance, i'd like to know how to do the same as you did but without passing it in the drawBall and moveBall functions.
ie: like I had tried to do before with ball1[i].drawBall(); etc

Thanks again!

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