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【フラクタル図形】樹木曲線の書き方

2023/08/30に公開

Ruby

class Broccoli < Base
  def call
    depth = 10                  # 複雑度
    v0    = wh * V[0.5, 1.0]    # 根元
    angle = 270.deg_to_rad      # 方向

    draw(v0, angle, depth)
  end

  def draw(v0, angle, depth)
    if depth <= 0
      return
    end
    stem_size = 9.0 * depth # 幹の長さ (depth を掛けることでだんだん幹が小さくなる)
    v1 = v0 + V.from_angle(angle) * stem_size
    line(v0, v1)
    snapshot
    draw(v1, angle - 20.deg_to_rad, depth - 1) # 左に伸びる幹
    draw(v1, angle + 20.deg_to_rad, depth - 1) # 右に伸びる幹
  end
end

アルゴリズム

v0 から angle の方向に幹を描く
その幹の先から二股に angle をずらして再度幹を描く

パラメータ次第でいろんな木ができる。たとえば、 angle をわずかに右方向にだけ向けるとすすきのようになる。

共通コード

require "#{__dir__}/../../物理/ベクトル/vec2"
require "rmagick"

include Magick

class Base
  include Math

  def call
  end

  def write(path)
    layer.write(path)
    puts path
    open path
  end

  def animation_write(path, delay: 2)
    av = image_list.optimize_layers(Magick::OptimizeLayer)
    av.delay = 100.0 / 60 * delay
    av.write(path)
    puts path
    open path
  end

  private

  def canvas_wh
    V[800, (800 / 1.618033988749895).to_i]
  end

  def wh
    canvas_wh
  end

  def title
    self.class.name.underscore
  end

  def snapshot
    image_list << layer.dup
  end

  def snapshot_counter
    @snapshot_counter ||= 0
    @snapshot_counter += 1
  end

  def open(path)
    system "open -a 'Google Chrome' #{path}"
  end

  def layer
    @layer ||= Image.new(*canvas_wh) do |e|
      e.background_color = background_color
    end
  end

  def image_list
    @image_list ||= ImageList.new
  end

  def background_color
    "white"
  end

  def foreground_color
    "grey30"
  end

  def line_width
    2
  end

  def color_from(iter)
    r = iter % 32 *  8
    b = iter %  8 * 32
    g = iter % 16 * 16
    "#%02x%02x%02x" % [r, g, b]
  end

  def draw_context
    g = Draw.new
    yield g
    g.draw(layer)
  end

  def line(v0, v1)
    draw_context do |g|
      g.stroke_width(line_width)
      g.stroke(foreground_color)
      g.line(*v0, *v1)
    end
  end

  def triangle(v0, v1, v2)
    draw_context do |g|
      g.fill("transparent")
      g.stroke_width(line_width)
      g.stroke(foreground_color)
      g.polygon(*v0, *v1, *v2)
    end
  end

  def pixel(v0, color)
    draw_context do |g|
      g.fill(color)
      g.rectangle(*v0, *v0)
    end
  end

  def rectangle(v0, v1, color: foreground_color)
    draw_context do |g|
      g.fill(color)
      g.rectangle(*v0, *v1)
    end
  end

  def rectangle_border(v0, v1)
    draw_context do |g|
      g.fill("transparent")
      g.stroke_width(1)
      g.stroke(foreground_color)
      g.rectangle(*v0, *v1)
    end
  end
end

if $0 == __FILE__
  require "rspec/autorun"
  RSpec.configure do |config|
    config.expect_with :test_unit
  end

  describe do
    it "works" do
    end
  end
end
# >> .
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アルゴリズム

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