let s;

function setup() {

  createCanvas(windowHeight, windowHeight);

  colorMode(HSB);

  s = width/4;

}

​

function draw() {

  background(0);

  stroke(255);

  strokeWeight(10);

  point(0, 2*s);

  point(s, s);

  point(mouseX, mouseY);

  point(3*s, s);

  point(4*s, 2*s);

  strokeWeight(5);

  noFill();

  quarticBezier(0, 2*s, s, s, mouseX, mouseY, 3*s, s, 4*s, 2*s);

  /*stroke(0, 255, 255);

  line(0, 2*s, s, s);

  line(3*s, s, 4*s, 2*s);*/

}

​

p5.Vector.quarterp = function(v1, v2, v3, v4, v5, t) {

  let l1 = p5.Vector.lerp(v1, v2, t);

  let l2 = p5.Vector.lerp(v2, v3, t);

  let l3 = p5.Vector.lerp(v3, v4, t);

  let l4 = p5.Vector.lerp(v4, v5, t);

  let q1 = p5.Vector.lerp(l1, l2, t);

  let q2 = p5.Vector.lerp(l2, l3, t);

  let q3 = p5.Vector.lerp(l3, l4, t);

  let c1 = p5.Vector.lerp(q1, q2, t);

  let c2 = p5.Vector.lerp(q2, q3, t);

  let quar = p5.Vector.lerp(c1, c2, t);

  return quar;

}

​

function quarticBezier(x1, y1, x2, y2, x3, y3, x4, y4, x5, y5) {

  beginShape();

  for(let t = 0; t <= 1.000000001; t += 0.01) {

    let v = p5.Vector.quarterp(createVector(x1, y1), createVector(x2, y2), createVector(x3, y3), createVector(x4, y4), createVector(x5, y5), t);

    vertex(v.x, v.y);

  }

  endShape();

}

​

function quarticBezierVertex(x1, y1, x2, y2, x3, y3, x4, y4, x5, y5) {

  for(let t = 0; t <= 1.000000001; t += 0.01) {

    let v = p5.Vector.quarterp(createVector(x1, y1), createVector(x2, y2), createVector(x3, y3), createVector(x4, y4), createVector(x5, y5), t);

    vertex(v.x, v.y);

  }

}