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]
}