yalbert-Intersections

var segs = [];
var intersections = [];
var clicked = false;
var numSegs = 12;
var lineLength = 300;
var dotSize = 20;
 
function setup() {
  angleMode(DEGREES);
  createCanvas(700, 700);
  resetLines();
  findIntersections();
}
 
function draw() {
  background(255);
 
  //creates a new set of segments if the mouse is clicked
  if(clicked){
    resetLines();
    findIntersections();
    clicked = false;
  }
  drawSegs();
  drawIntersections();
}
 
function drawSegs(){
  for(i = 0; i < numSegs; i++){
    segs[i].drawSeg();
  }
}
 
function drawIntersections(){
  for(i = 0; i< intersections.length; i++){
    intersections[i].drawIntersection();
  }
}
 
function mousePressed() {
  clicked = true;
}
 
function Segment(x1, x2, y1, y2){
  this.x1 = x1;
  this.x2 = x2;
  this.y1 = y1;
  this.y2 = y2;
  this.drawSeg = function(){
    stroke(0);
    strokeWeight(2);
    line(this.x1, this.y1, this.x2, this.y2);
  }
}
 
function Intersection(x, y){
  this.xPos = x;
  this.yPos = y;
  this.drawIntersection = function(){
    strokeWeight(0);
    fill(0, 100);
    ellipse(this.xPos, this.yPos, dotSize, dotSize);
  }
}
 
function resetLines(){
  segs = [];
  for(i = 0; i < numSegs; i++){
    var x1 = random(0, width);
    var y1 = random(0, height);
    var secondPoint = setSecondPoint(x1, y1);
    var x2 = secondPoint[0];
    var y2 = secondPoint[1];  
    newSeg = new Segment(x1, x2, y1, y2);
    segs.push(newSeg);
  }
}
 
//Calculates the second point by selecting a point at the edge of a circle
//where the radius is the desired length of the lines and the center
//is the first point
function setSecondPoint(x1, y1){
  var angle = random(0, 360);
  var y2 = sin(angle) * lineLength + y1;
  var x2 = cos(angle) * lineLength + x1; 
 
  //If the second point is outside the canvas, another one is calculated
  while(x2 < 0 || x2 >= width || y2 < 0 || y2 >= height){
    angle = random(0, 360);
    y2 = sin(angle) * lineLength + y1;
    x2 = cos(angle) * lineLength + x1; 
  }
 
  return [x2, y2];
}
 
//iterates through all of the segments to find the intersections
function findIntersections(){
  intersections = [];
  for(firstInd = 0; firstInd < numSegs; firstInd++){
    firstSeg = segs[firstInd];
    for(secInd = 0; secInd < numSegs; secInd++){
      secondSeg = segs[secInd];
      intersection = findIntersection(firstSeg.x1, firstSeg.y1, 
                                      firstSeg.x2, firstSeg.y2,
                                      secondSeg.x1, secondSeg.y1,
                                      secondSeg.x2, secondSeg.y2);
      if(intersectionIsValid(intersection)){
        intersections.push(new Intersection(intersection[0], intersection[1]));
      }
    }
  }
}
 
//check that the intersection exists and hasn't already been discovered
function intersectionIsValid(intersection){
  if(intersection == false){
    return false;
  }
  for(i = 0; i < intersections.length; i++){
    if(intersections[i].xPos == intersection[0] && intersections[i].yPos == intersection[1]){
      return false;
    }
  }
  return true;
}
 
//Paul Bourke's equation for finding the intersection of two lines
//Code courtesy of Leo Bottaro
function findIntersection(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
  }
 
  denominator = ((y4 - y3) * (x2 - x1) - (x4 - x3) * (y2 - y1))
 
  // Lines are parallel
  if (denominator === 0) {
    return false
  }
 
  let ua = ((x4 - x3) * (y1 - y3) - (y4 - y3) * (x1 - x3)) / denominator
  let 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
  let x = x1 + ua * (x2 - x1)
  let y = y1 + ua * (y2 - y1)
 
  return [floor(x), floor(y)]
}