title: Perlin noise not working (p5js)
body: <p>I'm using P5.js and the Perlin <code>noise()</code> function to try and draw a circle with Perlin noise generated <code>x</code> and <code>y</code> coordinates. I don't get any error messages but nothing is drawn on the canvas. What am I doing wrong?</p>
  
  <pre class="lang-js prettyprint-override"><code>let width;
  let height;
  
  function setup() {
      createCanvas(windowWidth, windowHeight);
      width = windowWidth;
      height = windowHeight;
  }
  
  var Circle = function () {
      this.x = width / 2;
      this.y = height / 2;
      this.tx = 0;
      this.ty = 0;
  };
  
  Circle.prototype.display = function () {
      stroke(0);
      ellipse(this.x, this.y, 200, 200);
  };
  
  Circle.prototype.walk = function () {
      this.x = map(noise(this.x), 0, 1, 0, width);
      this.y = map(noise(this.y), 0, 1, 0, height);
      this.tx += 0.01;
      this.ty += 0.01;
  };
  
  var c = new Circle();
  
  function draw() {
      c.walk();
      c.display();
  }
  </code></pre>
  
  <pre class="lang-html prettyprint-override"><code>&lt;html&gt;
  
  &lt;head&gt;
      &lt;meta charset="UTF-8"&gt;
      &lt;script language="javascript" type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/p5.js/0.6.1/p5.js"&gt;&lt;/script&gt;
  
      &lt;script language="javascript" type="text/javascript" src="sketch.js"&gt;&lt;/script&gt;
  
      &lt;style&gt;
          body {
              padding: 0;
              margin: 0;
          }
  
      &lt;/style&gt;
  &lt;/head&gt;
  
  &lt;/html&gt;
  </code></pre>