Why this line drawing animation shows up only when I put my variables on top of my coding?

soonk

Hello yall, I 'd like to draw lines with 20 pixels increments like below.

However, when I put "int x=0" after void draw(), I couldn't see anything.

Why it doesn't show anythiing?

Case one

int x = 0;

void setup() {
  size(400,300);
}

void draw() {
  background(0);
  strokeWeight(2);
  stroke(255);
  line (x,0,x,height);
  x = x+20;
}

case two

void setup() {
  size(400,300);
}

void draw() {
  int x = 0;
  background(0);
  strokeWeight(2);
  stroke(255);
  line (x,0,x,height);
  x = x+20;
}

Respar

I made this for you:

int x = 0; ArrayList<Integer> xHistory = new ArrayList<Integer>();
void setup() {
 size(400,300);
}
void draw() {
 background(0);
 strokeWeight(2);
 stroke(255);
 for (int next : xHistory) {
  line (next, 0, next, height);
 }
 if (x <= width) {
  xHistory.add(x);
  x += 20;
 } else {
  xHistory.clear();
  x = 0;
 }
} 

I apologize for the weird formatting, I'm new to the forums.

koogs

Draw is a loop, it is called repeatedly.

In case 1 it is called repeatedly and X increments because X is global, so you see lots of lines.

In case 2 it is called repeatedly but X is local so it's always 0. You see 1 line at x = 0, lots of times.

koogs

Read the FAQ about setup and draw.

And the one about formatting code.

koogs

And all the others whilst you are there.