Stuff

Author: monkstone

processing_app/topics/lsystems/library/koch/koch.rb

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+# Kochline class
+class KochLine
+  include Propane::Proxy
+  attr_reader :start, :finish
+
+  def initialize(a, b)
+    @start = a.copy
+    @finish = b.copy
+  end
+
+  def display
+    stroke(120)
+    line(start.x, start.y, finish.x, finish.y)
+  end
+
+  # This is easy, just 1/3 of the way
+  def kochleft
+    v = finish - start
+    v /= 3
+    v + start
+  end
+
+  # More complicated, using a little trig to figure out where this vector is!
+  def kochmiddle
+    v = finish - start
+    v /= 3
+    p = start.copy
+    p += v
+    rotate_line(v, -60)
+    p + v
+  end
+
+  # Easy, just 2/3 of the way
+  def kochright
+    v = start - finish
+    v /= 3
+    v + finish
+  end
+
+  private
+
+  def rotate_line(v, theta)
+    xtemp = v.x
+    # Might need to check for rounding errors like with angleBetween function?
+    v.x = v.x * DegLut.cos(theta) - v.y * DegLut.sin(theta)
+    v.y = xtemp * DegLut.sin(theta) + v.y * DegLut.cos(theta)
+  end
+end
+
+# KochFractal class
+class KochFractal
+  attr_reader :count, :start, :finish, :lines
+  def initialize(width, height)
+    @start = Vec2D.new(0, height - 20)
+    @finish = Vec2D.new(width, height - 20)
+    @lines = []
+    restart
+  end
+
+  def next_level
+    # For every line that is in the arraylist
+    # create 4 more lines in a new arraylist
+    @lines = iterate(lines)
+    @count += 1
+  end
+
+  def restart
+    @count = 0      # Reset count
+    lines.clear     # Empty the array list
+    lines << KochLine.new(start, finish)
+  end
+
+  def render
+    lines.each(&:display)
+  end
+
+  # This is where the **MAGIC** happens
+  # Step 1: Create an empty arraylist
+  # Step 2: For every line currently in the arraylist
+  #   - calculate 4 line segments based on Koch algorithm
+  #   - add all 4 line segments into the new arraylist
+  # Step 3: Return the new arraylist and it becomes the list of line segments
+  # for the structure. As we do this over and over again, each line gets broken
+  # into 4 lines, which gets broken into 4 lines, and so on. . .
+  def iterate(before)
+    [].tap do |now|    # Create empty list
+      before.each do |l|
+        # Calculate 5 koch vectors (done for us by the line object)
+        a = l.start
+        b = l.kochleft
+        c = l.kochmiddle
+        d = l.kochright
+        e = l.finish
+        # Make line segments between all the vectors and add them
+        now << KochLine.new(a, b)
+        now << KochLine.new(b, c)
+        now << KochLine.new(c, d)
+        now << KochLine.new(d, e)
+      end
+    end
+  end
+end