CSC111 FractalTree.py

--D. Thiebaut (talk) 07:45, 29 April 2014 (EDT)

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Fractal Tree

# practalTree.py
# D. Thiebaut
# Code taken from http://openbookproject.net/thinkcs/python/english3e/recursion.html
# and adapted to work with graphics111.py.
#
# Draws a fractal tree on the graphic window.
#
from graphics111 import *
import math
import time
import random

# dimensions of the window
MAXWIDTH = 800
MAXHEIGHT = 800

# recursive tree-drawing function
# 
def draw_tree(canvas,       # the canvas
              order,        # the level of recursion.  Starts positive.
              theta,        # angle of new branch leaving this trunk
              sz,           # size of this branch
              x, y,         # coordinates of base of this branch
              heading       # angle of direction of this branch
              ):    

   trunk_ratio = 0.29       # How big is the trunk relative to whole tree?
   trunk = sz * trunk_ratio # length of trunk

   # compute x, y of end of the current branch
   delta_x = trunk * math.cos(heading)
   delta_y = trunk * math.sin(heading)
   x2, y2 = x + delta_x, y + delta_y

   # draw current branch
   canvas.setFill( 0,0,0 )
   canvas.drawLine(x, y, x2, y2)

   # if this branch has sub-branches, then recurse
   if order > 0:    
       
      # make the recursive calls to draw the two subtrees
      newsz = sz*(1 - trunk_ratio)
      draw_tree(canvas,
                order-1, theta, newsz, x2, y2, heading-theta )
      draw_tree(canvas,
                order-1, theta, newsz, x2, y2, heading+theta )


# draw 1 tree in the middle of the screen, shooting straight up.
def main():
    win = GraphicsWindow(MAXWIDTH, MAXHEIGHT)
    canvas = win.canvas()
    theta = 0.01      # use 0.02 for tall skinny trees, 0.7 for fat trees
    draw_tree(canvas,
              9,
              theta,
              MAXWIDTH*0.9, MAXWIDTH//2,
              MAXHEIGHT-50,
              -math.pi/2)
        
    win.wait()
    win.close()

main()