ookey-Intersections

var linecount = 12;
var linelen = 200;
var linearray = [];
var circleRad = 15;
var bckgrnd = '#fbd2d7';
 
function setup() { 
  createCanvas(720, 480);
} 
 
function draw() {
 
  background(bckgrnd);
	drawlines(linearray);
  drawintersect(linearray);
}
 
function drawlines(a)
{
  strokeWeight(2);
  stroke('#000000');
  for (i = 0; i < a.length; i++)
  {
    //each element should be an array of four integers
    x1 = a[i][0];
    y1 = a[i][1];
    x2 = a[i][2];
    y2 = a[i][3];
    line(x1,y1,x2,y2);
  }
}
 
function drawintersect(a)
{
  fill(color(50, 55, 100, 90));
  noStroke();
  intersects = calcintersect(a);
  for (i = 0; i < intersects.length; i++)
  {
    ellipse(intersects[i][0], intersects[i][1],
            circleRad, circleRad);
  }
}
 
//using equations from Paul Bourke
function calcintersect(a)
{
  inter = [];
  for (i = 0; i < a.length; i++)
  {
    [x1, y1, x2, y2] = a[i];
    for (j = i + 1; j < a.length; j++)
    {
      	[x3, y3, x4, y4] = a[j];
        ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) /
          ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1));
        ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) /
          ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1));
        if ((0 < ua) && (ua < 1) && (0 < ub) && (ub < 1))
        {
          x = x1 + ua * (x2 - x1);
          y = y1 + ua * (y2 - y1);
          inter.push([x,y]);
        }
    }
  }
  return inter;
}
 
function mouseClicked() {
  linearray = [];
 
  for (i = 0; i < linecount; i++)
  {
    x1 = Math.floor(Math.random() * width);
    y1 = Math.floor(Math.random() * height);
    x2 = (Math.floor(Math.random() * (2 * linelen)) - linelen) + x1;
    y2 = Math.floor(Math.pow((Math.pow(linelen,2) - 
         Math.pow(x2 - x1, 2)), 0.5)) + y1;
    linearray.push([x1, y1, x2, y2]);
  }
}