Non-Parametric version of a parametric L-System

image.png

image2.png

nonparametric_lsystem.rb

# encoding: utf-8

# A non-parametric version of this L-System:
# http://codepen.io/josh_cheek/details/yVoqvO/

# Install deps: $ gem install graphics -v 1.0.0b6
# Run:          $ rsdl thisfile.rb

require 'graphics'

width, height = 800, 600
simulation    = Graphics::Drawing.new width, height, 24
rules         = {'A'=>'F-AA-F', 'F'=>'GG', 'G'=>'F'}
production    = 12.times.reduce('A') { |prod| prod.gsub /#{rules.keys.join '|'}/, rules }
x, y          = width/2, 108
ø, ∆ø         = Math::PI/2, Math::PI/2 # start facing up with right-angle turns
stride        = 3

simulation.register_color :edgy_blue, 50, 150, 255
simulation.clear :black                             # canvas background
simulation.rect 180, 80, 440, 440, :edgy_blue, true # image frame
simulation.rect 190, 90, 420, 420, :gray10,    true # image background

production.each_char do |char|
  case char
  when '-' then ø += ∆ø
  when '+' then ø -= ∆ø
  when 'F', 'G'
    old_x, old_y = x, y
    x += stride*Math.cos(ø).round
    y += stride*Math.sin(ø).round
    simulation.line old_x, old_y, x, y, :edgy_blue
  end
end
simulation.run