Bezier With Sindy (Ruby version)

bezier_with_sindy.rb

# The JavaScript version is @ http://codepen.io/josh_cheek/pen/VpBJVQ?editors=0010
require 'graphics'

class BezierForSindy < Graphics::Simulation
  def initialize
    super 500, 500, 24
    @initial_points = [
      [50,     h-50],
      [50,     50],
      [w/2-50, h-50],
      [w-50,   h-50],
      [w-50,   50],
    ]
    @bezier_points = []
    @iteration     = 0
    @direction     = 1
    @ticks         = 100
    @radius        = 4
  end

  def draw(n)
    clear :white
    points = @initial_points
    while points.length > 1
      draw_lines_between(points)
      draw_every_endpoint(points)
      points = get_next_points(points, @iteration/@ticks.to_f)
    end

    @bezier_points[@iteration] = points[0]
    crnt_bezier_points = @bezier_points[0, @iteration] # we fill in more points than we need
    draw_lines_between(crnt_bezier_points)
    draw_first_and_last_endpoint(crnt_bezier_points)

    if @iteration === @ticks
      @direction = -1
    elsif @iteration == 0
      @direction = 1
    end
    @iteration = @iteration + @direction
  end


  def draw_lines_between(points)
    points.each_cons 2 do |(x1, y1), (x2, y2)|
      line x1, y1, x2, y2, :black
    end
  end

  def draw_every_endpoint(points)
    points.each { |point| circle point[0], point[1], @radius, :black, true }
  end

  def draw_first_and_last_endpoint(points)
    if points.length > 0
      first_point = points.first
      last_point  = points.last
      circle first_point[0], first_point[1], @radius, :black, true
      circle last_point[0],  last_point[1],  @radius, :black, true
    end
  end

  def get_next_points(points, percentage)
    points.each_cons(2).map do |(x1, y1), (x2, y2)|
      x = (x2 - x1) * percentage + x1
      y = (y2 - y1) * percentage + y1
      [x, y]
    end
  end
end

BezierForSindy.new.run