// Daniel Shiffman

// http://natureofcode.com

​

// Recursive Tree

// Renders a simple tree-like structure via recursion

// Branching angle calculated as a function of horizontal mouse position

​

let angle;

​

function setup() {

  createCanvas(640, 240);

}

​

function draw() {

  background(255);

  // Mapping the angle between 0 to 90° (HALF_PI) according to mouseX

  angle = map(mouseX, 0, width, 0, HALF_PI);

​

  // Start the tree from the bottom of the canvas

  translate(width / 2, height);

  stroke(0);

  strokeWeight(2);

  branch(80);

}

​

//{!1} Each branch now receives its length as an argument.

function branch(len) {

  line(0, 0, 0, -len);

  translate(0, -len);

​

  //{!1} Each branch’s length shrinks by two-thirds.

  len *= 0.67;

​

  if (len > 2) {

    push();

    rotate(angle);

    //{!1} Subsequent calls to branch() include the length argument.

    branch(len);

    pop();

​

    push();

    rotate(-angle);

    branch(len);

    pop();

  }

}

​