shuann-Intersections

var lineNum = 12;//change this number to get more lines 

var lineSets = [];

function setup() {

  createCanvas(720, 480);

  lineGenerator();

}

function draw() {

  background(255);

​

  for (var j = 0; j < lineNum; j++){

    var x1 = lineSets[j][0];

    var y1 = lineSets[j][1];

    var x2 = lineSets[j][2];

    var y2 = lineSets[j][3];

    line(x1, y1, x2, y2);

    for (var s = 0; s < lineNum; s++){

      var x3 = lineSets[s][0];

      var y3 = lineSets[s][1];

      var x4 = lineSets[s][2];

      var y4 = lineSets[s][3];

      if (intersect(x1, y1, x2, y2, x3, y3, x4, y4) != false){

        var cCenter = intersect(x1, y1, x2, y2, x3, y3, x4, y4);

        fill("pink");

        ellipse(round(cCenter[0]), round(cCenter[1]), 10);

      }

    }

  }

  text("Number of Lines:" + lineNum, 10 ,20);

  text("* Up/Down Key to Increase/Decrease *", 10 ,35);

}

function mousePressed() {

  lineGenerator();

}

​

function keyPressed() {

  if (keyCode === UP_ARROW) {

    lineNum += 1;

    lineGenerator();

  } else if (keyCode === DOWN_ARROW) {

    lineNum -= 1;

    lineGenerator();

  }

}

​

function lineGenerator(){

  lineSets = [];

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

    var x1 = round(random(0,width+1));

    var y1 = round(random(0,height+1));

    var x2 = round(random(0,width+1));

    var y2 = round(random(0,height+1));

    lineSets[i] = [x1, y1, x2, y2]

  }

}

​

// taken and modified from http://paulbourke.net/geometry/pointlineplane/javascript.txt

// line intercept math by Paul Bourke http://paulbourke.net/geometry/pointlineplane/

// Determine the intersection point of two line segments

// Return FALSE if the lines don't intersect

function intersect(x1, y1, x2, y2, x3, y3, x4, y4) {

​

  // Check if none of the lines are of length 0

  if ((x1 === x2 && y1 === y2) || (x3 === x4 && y3 === y4)) {

    return false

  }

​

  var denominator = ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))

​

  // Lines are parallel

  if (denominator === 0) {

    return false

  }

​

  var ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denominator

  var ub = ((x2 - x1) * (y1 - y3) - (y2 - y1) * (x1 - x3)) / denominator

​

  // is the intersection along the segments

  if (ua < 0 || ua > 1 || ub < 0 || ub > 1) {

    return false

  }

​

  // Return a object with the x and y coordinates of the intersection

  var x = x1 + ua * (x2 - x1)

  var y = y1 + ua * (y2 - y1)

​

  return [x, y]

}