#MonthOfCode day 19 - tree

day_19.py

# this program draws a random TREE-LIKE shape, inspired by L-Systems
import pygame
from time import sleep
import random
import sys
DISP_WIDTH = 640
DISP_HEIGHT = 480

def randPeriod():
    return random.choice((1, 16,  64) ) #determines the slope with wich the emerging branch grows

class MovingPix():
    def __init__(self , x,y, vert_grow=None, period=None ):
        self.x =  x
        self.y =  y
        self.vert_grow = random.choice((True,False)) if vert_grow==None else vert_grow
        self.period =randPeriod() if period==None else period  
    def isOut( self):
        #is it out of bounds?
        return( self.y>=DISP_HEIGHT
            or self.x>=DISP_WIDTH
            or self.x<0
            or self.y<0  )

    def simulateGrowth(self,  i ):
        res = [ self.x, self.y ]
        if self.vert_grow:
            res[1]+=1
            if i%self.period==0:
                res[0]+=1
        else:
            res[0]+=1
            if i%self.period==0:
                res[1]+=1

        return MovingPix( res[0], res[1], self.vert_grow, self.period)

    def letGrowthDirMutate(self):
        if(  random.randint(1,8)==8):
            self.period = randPeriod()

    def display(self, window):
        window.set_at(  (self.x, self.y),  pygame.Color('BLACK') )

def refreshScreen():
    window.fill(  pygame.Color('WHITE') )
    for pix in pixel_list:
        pix.display( window)
    pygame.display.flip() 

# init. pygame libr; create the screen and diplays a help message in the console
pygame.init() 
window = pygame.display.set_mode( (DISP_WIDTH, DISP_HEIGHT) )

# diplays the state and then loops for input handling 
pixel_list = list()
growing_pix = list()
tmp_pix = MovingPix(10,10)
pixel_list.append( tmp_pix)
growing_pix.append( tmp_pix)

counter=0
branch_proba_adjuster = 2
drawing =True
while True: 
    # in case the user wants to abord
    for event in pygame.event.get(): 
        if event.type == pygame.QUIT: 
            pygame.quit()
            sys.exit(0) 
    if not drawing:
        continue

    # simulating growth
    n_growing_pix = list()
    for gpix in growing_pix:
        tmp_pix = gpix.simulateGrowth( counter )
        if( gpix.isOut() ):
            continue
        pixel_list.append( tmp_pix)
        n_growing_pix.append( tmp_pix )
        tmp_pix.letGrowthDirMutate()
    
        #branching possibility
        if( random.randint(1,4+branch_proba_adjuster)==4+branch_proba_adjuster ):  #the more branches, the smaller the probability to branch
            branch_proba_adjuster=branch_proba_adjuster+(4*4)
            branched_pix =MovingPix(tmp_pix.x, tmp_pix.y,not tmp_pix.vert_grow)
            pixel_list.append( branched_pix)
            n_growing_pix.append( branched_pix)
    growing_pix = n_growing_pix 
    counter+=1

    # drawing-halt condition
    if( 0==len(growing_pix )):
        drawing=False
        print "drawing done."

    # display + delay
    refreshScreen()
    sleep(0.001)