Exercise 13-3: Complete the following code which uses Perlin noise to set the location of a circle. Run the code. Does the circle appear to be moving “naturally”? 
// Noise "time" variables  
// In this sketch, we want to use noise for two different values. So that the output 
// of the noise function is not identical, we start at two different points in time. 
float xtime = 0.0;  
float ytime = 100.0;
float increment = 0.01;  

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

void draw() {   
  background(0);  
  float x = ____________________________________;  
  float y = ____________________________________;  
  ____________________________________;  
  ____________________________________;  
  // Draw the ellipse with position determined by Perlin noise  
  fill(200);  
  ellipse(__________,__________,__________,__________);  
}
Example

exercise_13_3

// Learning Processing
// Daniel Shiffman
// http://www.learningprocessing.com

// Exercise 13-3: Complete the following code which uses Perlin noise to set the location of 
// a circle. Run the code. Does the circle appear to be moving  "naturally"?  

// Noise "time" variables  
// In this sketch, we want to use noise for two different values. So that the output 
// of the noise function is not identical, we start at two different points in time. 
float xtime = 0.0;  
float ytime = 100.0;
float increment = 0.01;  

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

void draw() {   
  background(255);  
  float x = noise(xtime)*width;  
  float y = noise(ytime)*height;  
  xtime += increment;  
  ytime += increment;  
  // Draw the ellipse with size determined by Perlin noise  
  stroke(0);
  fill(175);  
  ellipse(x,y,16,16);  
}

2 Comments
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  1. Should the comment above the fill statement not be “Draw the ellipse with position determined by Perlin noise” rather than “size”?

    Comment by Kit — August 4, 2009 @ 6:48 am

  2. Whoops yes, fixed now!

    Comment by admin — August 5, 2009 @ 1:22 pm

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