sierpinski arrowhead

Author: monkstone

processing_app/topics/lsystems/data/java_args.txt

@@ -0,0 +1,84 @@
+
+load_libraries :grammar
+attr_reader :points
+
+def setup
+  sketch_title 'Sierpinski Arrowhead'
+  sierpinski = SierpinskiArrowhead.new(Vec2D.new(width * 0.15, height * 0.7))
+  production = sierpinski.generate 6 # 6 generations looks OK
+  @points = sierpinski.translate_rules(production)
+  no_loop
+end
+
+def draw
+  background(0)
+  render points
+end
+
+def render(points)
+  no_fill
+  stroke 200.0
+  stroke_weight 3
+  begin_shape
+  points.each_slice(2) do |v0, v1|
+    v0.to_vertex(renderer)
+    v1.to_vertex(renderer)
+  end
+  end_shape
+end
+
+def renderer
+  @renderer ||= GfxRender.new(g)
+end
+
+def settings
+  size(800, 800)
+end
+
+# SierpinskiArrowhead class
+class SierpinskiArrowhead
+  include Processing::Proxy
+  attr_reader :draw_length, :pos, :theta, :axiom, :grammar
+  DELTA = PI / 3 # 60 degrees
+  def initialize(pos)
+    @axiom = 'XF' # Axiom
+    rules = {
+      'X' => 'YF+XF+Y',
+      'Y' => 'XF-YF-X'
+    }
+    @grammar = Grammar.new(axiom, rules)
+    @theta = 0
+    @draw_length = 200
+    @pos = pos
+  end
+
+  def generate(gen)
+    @draw_length = draw_length * 0.6**gen
+    grammar.generate gen
+  end
+
+  def forward(pos)
+    pos + Vec2D.from_angle(theta) * draw_length
+  end
+
+  def translate_rules(prod)
+    [].tap do |pts| # An array to store line vertices as Vec2D
+      prod.scan(/./) do |ch|
+        case ch
+        when 'F'
+          new_pos = forward(pos)
+          pts << pos << new_pos
+          @pos = new_pos
+        when '+'
+          @theta += DELTA
+        when '-'
+          @theta -= DELTA
+        when 'X', 'Y'
+        else
+          puts("character #{ch} not in grammar")
+        end
+      end
+    end
+  end
+end
+