var boolDoRefresh;

var coll;

​

function setup() {

  createCanvas(640, 480);

  coll = new Array(num);

  for(var p = 0; p < coll.length; p++){

    coll[p] = new Array(4);

  }  

  boolDoRefresh = true;

  num = 12;

}

​

function draw() {

  if (boolDoRefresh) {

    background(220);

    for (var i = 0; i < num; i++) {

      let r1 = random(640);

      let r2 = random(480);

      let r3 = random(640);

      let r4 = random(480);

      fill(0);

      stroke(0);

      line(r1, r2, r3, r4);

      coll[i] = [r1, r2, r3, r4];

      coll[i][1] = r2;

      coll[i][2] = r3;

      coll[i][3] = r4;

    }

    for (var j = 0; j < num - 1; j++) {

      for (var k = j + 1; k < num; k++) {

        let num1 = (coll[k][2] - coll[k][0]) * (coll[j][1] - coll[k][1]) - (coll[k][3] - coll[k][1]) * (coll[j][0] - coll[k][0]);

        let num2 = (coll[j][2] - coll[j][0]) * (coll[j][1] - coll[k][1]) - (coll[j][3] - coll[j][1]) * (coll[j][0] - coll[k][0]);

        let denom = (coll[k][3] - coll[k][1]) * (coll[j][2] - coll[j][0]) - (coll[k][2] - coll[k][0]) * (coll[j][3] - coll[j][1]);

        var u1 = num1/denom;

        var u2 = num2/denom;

        var check = u1 >= 0 && u1 <= 1 && u2 >= 0 && u2 <= 1;

        if (denom != 0 && (num1 != 0 || num2 != 0) && check) {

          var x = coll[j][0] + u1 * (coll[j][2]-coll[j][0]);

          var y = coll[j][1] + u1 * (coll[j][3]-coll[j][1]);

          fill('rgba(10, 255, 180, .5)');

          stroke(10, 255, 180);

          circle(x, y, 15);

        }

      }

    }

  }

  boolDoRefresh = false;

}

​

function mousePressed() {

  boolDoRefresh = true;

}