// by sampling a circle into many segments, 

// and then locally averaging each point with its neighbors, 

// except for the three special corner vertices.

// Golan Levin, January 2017

​

var radius;

var cx, cy;

var nCirclePoints = 120;

var circlePoints = [];

​

//-----------------------------------------

function setup() {

  createCanvas(400, 400);

  radius = width / 2 * 0.75;

  cx = width / 2;

  cy = height / 2;

​

  for (var i = 0; i < nCirclePoints; i++) {

    var t = map(i, 0, nCirclePoints, 0, TWO_PI) - HALF_PI;

    var x = cx + radius * cos(t);

    var y = cy + radius * sin(t);

    circlePoints[i] = {

      x, y

    };

  }

}

​

//-----------------------------------------

function draw() {

  background(255);

  noFill();

  stroke(0);

  strokeWeight(3);

​

  beginShape();

  for (var i = 0; i < nCirclePoints; i++) {

    if (i % (nCirclePoints / 3) !== 0) {

      var h = (i - 1 + nCirclePoints) % nCirclePoints;

      var j = (i + 1 + nCirclePoints) % nCirclePoints;

      circlePoints[i].x = (circlePoints[h].x + circlePoints[i].x + circlePoints[j].x) / 3.0;

      circlePoints[i].y = (circlePoints[h].y + circlePoints[i].y + circlePoints[j].y) / 3.0;

    }

    vertex(circlePoints[i].x, circlePoints[i].y);

  }

  endShape(CLOSE);

}

​