シェルピンスキー曲線

turtle_sierpinski_curve.rb

require 'oekaki'
require_relative 'turtle'

Width, Height = 600, 600

Oekaki.app width: Width, height: Height, title: "Sierpinski curve" do
  draw do
    clear
    
    depth = 5
    l = 550
    num = 2 ** (depth - 1)
    
    t = Turtle.new(Width, Height, self)
    t.color(0xffff, 0, 0xffff)
    step = l / ((2 * sqrt(2) + 1) * num + num - 1)
    t.move(-l / 2 + step / sqrt(2), l / 2)
    
    drawing = lambda do |depth, angle = 45|
      if depth.zero?
        t.forward(step)
      else
        t.right(angle)
        drawing[depth - 1, -angle]
        t.left(angle)
        t.forward(step)
        t.left(angle)
        drawing[depth - 1, -angle]
        t.right(angle)
      end
    end
    
    4.times do
      drawing[2 * depth - 1]
      t.right(45)
      t.forward(step)
      t.right(45)
    end
  end
end