Intersections

//defining constants

const WIDTH = 720;

const HEIGHT = 480;

const BACK_COLOR = 'rgb(172, 230, 230)';

const NUM_LINES = 100;

const LINE_LEN = 250;

const LINE_COLOR = 'rgb(0, 86, 86)';

const LINE_STROKE = 2;

const CIR_CIR = 12;

const CIR_COLOR = 'rgba(11, 140, 140, 0.5)';

​

//global variables

var pointList = [];

var intsecList = [];

​

function setup() 

{

  createCanvas(WIDTH, HEIGHT);

  background(BACK_COLOR);

  angleMode(DEGREES);

}

​

/* Lines functions.

   These are created by generating a random start point and slope and then uses trig 

   to get the end points from that data.*/

​

function drawLine() 

{

  stroke(LINE_COLOR);

  strokeWeight(LINE_STROKE);

  var x1 = random(50, WIDTH-50);

  var y1 = random(50, HEIGHT-50);

  var angle = random(360);

  var endHeight = LINE_LEN*sin(angle);

  var endLength = LINE_LEN*cos(angle);

  var x2 = x1 + endLength;

  var y2 = y1 + endHeight;

  line(x1,y1,x2,y2);  

  var linePoint = [x1,y1,x2,y2];

  pointList.push(linePoint);

} 

​

//source for intersect formulas: http://paulbourke.net/geometry/pointlineplane/

function grabIntersects(points)

{

  var x1 = points[0], y1 = points[1],

      x2 = points[2], y2 = points[3],

      x3 = points[4], y3 = points[5],

      x4 = points[6], y4 = points[7];

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

  if (den != 0)

  {

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

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

    if (0 <= ua && ua <= 1 && 0 <= ub && ub <= 1)

    {

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

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

      intsecList.push([x,y]);

    }

  }

} 

​

function drawCircles()

{

  noStroke();

  fill(CIR_COLOR);

  while (intsecList.length != 0)

  {

    var points = intsecList.shift();

    ellipse(points[0], points[1], CIR_CIR);

  }

}

​

function draw() 

{

  setup();

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

  {

    drawLine();

    for (var j = 0; j < pointList.length-1; j++)

    { 

      grabIntersects(pointList[j].concat(pointList[pointList.length-1]));

    }

  }

  drawCircles();

  pointList = [];

  intsecList = [];

  noLoop();

}

​

function mouseClicked()

{

  redraw();

}