Spoon-Intersections

var boolDoRefresh;

const NUM_LINES = 12;

function setup() {

  createCanvas(720, 480);

  background('#FFFFFF');

  strokeWeight(5);

  boolDoRefresh = true;

}

function draw() {

  if(boolDoRefresh) {

    background('#FFFFFF');

    var lines = constructLines();

    findIntersections(lines);

    boolDoRefresh = false;

  }

}

function mousePressed() {

  boolDoRefresh = true;

}

​

function constructLines() {

  const LINE_LENGTH = 250;

  var lines = [];

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

    var x1 = random(720);

    var y1 = random(480);

    var x2 = random(100) > 50 ? x1 - random(LINE_LENGTH) : x1 + random(LINE_LENGTH);

    var y2 = ((random(100) > 50 ? 1 : -1) * sqrt(sq(LINE_LENGTH) - sq(x1 - x2))) + y1;

    line(x1, y1, x2, y2);

    lines[i] = [x1, y1, x2, y2];

  }

  return lines;

}

​

function findIntersections(lines) {

  //uses calculations found at http://paulbourke.net/geometry/pointlineplane/

  //draws circles around any points where lines intersect

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

    for(var j = i + 1; j < NUM_LINES; j++) {

      var x1 = lines[i][0];

      var x2 = lines[i][2];

      var y1 = lines[i][1];

      var y2 = lines[i][3];

​

      var x3 = lines[j][0];

      var x4 = lines[j][2];

      var y3 = lines[j][1];

      var y4 = lines[j][3];

​

      var u1 = (((x4 - x3) * (y1 - y3)) - ((y4 - y3) * (x1 - x3)))

           / (((y4 - y3) * (x2 - x1)) - ((x4 - x3) * (y2 - y1)));

      var u2 = (((x2 - x1) * (y1 - y3)) - ((y2 - y1) * (x1 - x3)))

           / (((y4 - y3) * (x2 - x1)) - ((x4 - x3) * (y2 - y1)));

      if(u1 > 0 && u1 < 1 && u2 > 0 && u2 < 1) {

        var x = x1 + (u1 * (x2 - x1));

        var y = y1 + (u1 * (y2 - y1));

        fill('#FFC600');

        ellipse(x, y, 15);

      }

    }

  }

}