radius = 100.0;

    nSteps = 150; 

    myLoopingNoiseArray = [];

​

var offscreenImg;

​

function setup() {

  createCanvas(300, 400); 

  makeOffscreenImg(); 

}

​

function draw() {

  background(0); 

  image(offscreenImg, 0, 0);

​

  currStep = frameCount % nSteps;

  var t = map(currStep, 0, nSteps, 0, TWO_PI); 

  var px = width/2.0 + radius * cos(t); 

  var py = width/2.0 + radius * sin(t);

  noStroke(); 

  fill(255); 

  ellipse(px, py, 7, 7); 

​

  noiseAtLoc = height - 100.0*noise(myScale*px, myScale*py);

  myLoopingNoiseArray[currStep] = noiseAtLoc;

  noFill(); 

  stroke(255); 

  beginShape(); 

  for (i=0; i<nSteps; i++) {

    nx = map(i, 0, nSteps-1, 0, width); 

    ny = myLoopingNoiseArray[i];

    vertex(nx, ny);

  }

  endShape(); 

​

  noStroke(); 

  fill(255); 

  ex = map(currStep, 0, nSteps-1, 0, width); 

  ellipse(ex, noiseAtLoc, 7, 7);

​

  // Save frames for the purpose of 

  // making an animated GIF loop, 

  // e.g. with http://gifmaker.me/

  // if ((frameCount >= nSteps) && (frameCount < (nSteps*2))) {

  //   saveFrame( "save/"+ nf(currStep, 3)+ ".jpg");

  // }

}

​

// Stash an image of the noise field. 

// Doing so is faster than recomputing it every frame. 

function makeOffscreenImg() {

  offscreenImg = createGraphics(width, width);

  // offscreenImg.beginDraw();

  for (x = 0; x<width; x++) {

    for (y = 0; y<width; y++) {

      offscreenImg.stroke(255.0*noise(myScale*x, myScale*y));

      offscreenImg.point(x, y);

    }

  }

}