let iterationAmt;

​

function setup() {

  createCanvas(640, 480);

  refresh = true;

  iterationAmt = createSlider(2, 100, 12);

}

​

function draw() {

  if (refresh) {

    const iterations = iterationAmt.value();

    let startpointsx = createPoints(iterations, width);

    let startpointsy = createPoints(iterations, height);

    let endpointsx = createPoints(iterations, width);

    let endpointsy = createPoints(iterations, height);

    let intpts = [];

    for (let i = 0; i < iterations; i++) {

​

      let pt;

      for (let j = 0; j < iterations; j++) {

        if (j != i) {

          pt = intersect(startpointsx[i], startpointsy[i], endpointsx[i], endpointsy[i], startpointsx[j], startpointsy[j], endpointsx[j], endpointsy[j]);

​

          if (pt.x > -1 || pt.y > -1) {

            intpts.push(pt);

          }

        }

      }

      stroke(200);

      line(

        startpointsx[i], startpointsy[i],

        endpointsx[i], endpointsy[i]

      );

    }

    // So white circles are on top

    for (let i = 0; i < intpts.length; i++)

    {

      stroke(50);

      ellipse(intpts[i].x, intpts[i].y, 10, 10);

    }

    refresh = false;

  }

}

​

function createPoints(iterations, max) {

  let points = [];

  for (let i = 0; i < iterations; i++) {

    points[i] = random(0, max);

  }

  return points;

}

​

// line intercept math by Paul Bourke 

// small modification to return -1 instead of false to stick with numbers (since the domain and range of the project is [0, width] [0, height]) by Lukas Hermannrespectively

//http://paulbourke.net/geometry/pointlineplane/

// Determine the intersection point of two line segments

// Return -1 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 -1

  }

​

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

​

  // Lines are parallel

  if (denominator === 0) {

    return -1

  }

​

  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 -1

  }

​

  // 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 {

    x,

    y

  }

}

​

function mouseClicked() {

  refresh = true;

  console.log(iterationAmt.value());

  background(255);

}