Chapter 4: Variables: Exercise 4-4: Recreate screenshots

A)

void setup() {
  size(200,200); 
  smooth();
}

void draw() {
  background(255);
  stroke(0);
  fill(175);
  ellipse(50,50,50,50);
  ellipse(150,50,50,50);
  ellipse(50,150,50,50);
  ellipse(150,150,50,50);
}

B)

void setup() {
  size(200,200); 
  smooth();
}

void draw() {
  background(255);
  stroke(0);
  line(100,0,100,100);
  line(100,100,0,200);
  line(100,100,200,200);
}

C)

void setup() {
  size(200,200); 
  smooth();
}

void draw() {
  background(255);
  stroke(0);
  rectMode(CENTER);
  fill(175);
  rect(100,100,175,175);
  fill(255);
  ellipse(100,100,75,75);
}

Example Step 3 Answer:

float centerX = 100;
float centerY = 100;

void setup() {
  size(200,200); 
  smooth();
}

void draw() {
  background(255);
  stroke(0);
  line(width/2,0,centerX,centerY);
  line(centerX,centerY,0,height);
  line(centerX,centerY,width,height);
  
  centerX += random(-1,1);
  centerY += random(-1,1);
  
  centerX = constrain(centerX,0,width);
  centerY = constrain(centerY,0,height);
}

Comments (2)

2 Comments

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1. Hi I’ve attempted adding variable to A) with the intention of making it track from left to right but nothing is happening. What am I doing wrong?

   int circleX = 50;
   int circleY = 50;
   int circleSize = 50;
   int circleFill = 0;
   int speed = 1;

   // basic setup
   void setup() {
   size(200,200);
   background(255);
   smooth();
   }

   void draw() {
   stroke(0);
   fill(0);
   // circle top left
   ellipse(circleX,circleY,circleSize,circleSize);
   // circle top right
   ellipse(150,50,50,50);
   // circle bottom left
   ellipse(50,150,50,50);
   // circle bottom right
   ellipse(150,150,50,50);
   }

   void move() {
   circleX = circleX + speed;
   if (circleX > width) {
   circleX = 10;
   }
   }

   void display() {
   fill(circleFill);
   ellipse(circleX,circleY,circleSize,circleSize);
   }

   also do you know how I would create the > symbol on a mac because at the moment I can only copy and paste it. I’ve tried alt + every key available but still no joy

   Thank you

   Comment by Dolsign — January 6, 2010 @ 7:26 am

2. You created the move() and display() functions, but never call them anywhere. Only draw() is called automatically by Processing so you’ll need to explicitly call your user-defined functions, i.e.

   void draw() {
     move();
     // etc.
   }
   

   ‘>’ is SHIFT-PERIOD on my mac.

   Comment by Daniel Shiffman — January 7, 2010 @ 9:01 am

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