[Visualpython-users] Fractals

[Michael Katz-H. <mi...@go...>]

A friend and I were remembering the days of LOGO...

He downloaded an implementation of LOGO and wrote a function to
draw the 'dragon' fractal.

I did them same but in VPython...it is attached here.

-Michael

P.S. - I get some weird screen artifacts when using curves to draw the
fractals, I am assuming this is just a bug in the OpenGL implementation (I
have only tried this in Linux)

## The dragon fractal
##
## The arguements to dragon are the iterations and the "size"
## dragon(iterations,size) size has little meaning since vpython
## autoscales

from visual import *

curr = vector(0,0,0)
dir = vector(0,1,0)
colors = [color.red,color.green,color.blue,color.yellow,color.magenta]
col = color.red

def forward(size):
    global curr
    global col
    global drag
    for s in arange(0,size,size/50.):
        drag.append(pos=(curr+dir),color=col)
        curr = curr+dir

def right(ang):
    global dir
    dir = rotate(dir,angle=-ang,axis=(0,0,1))


def left(ang):
    global dir
    dir = rotate(dir,angle=ang,axis=(0,0,1))


def step(iter,size,rev,pc):
    global curr
    global dir
    if iter==0:
        forward(size)
        return
    if rev==0:
        step(iter-1,size,rev,pc)
        right(pi/2)
        step(iter-1,size,1-rev,pc)
    else:
        global col
        if pc==0:
            col = colors[(iter%5)]
        step(iter-1,size,1-rev,1)
        left(pi/2)
        step(iter-1,size,rev,1)

def dragon(iter,size):
    global drag
    drag = curve()
    step(iter,size,0,0)


dragon(11,10)

-- 
/-------------------------------------------------------------\
| Michael Katz-Hyman	                  mz...@an... |
| Pittsburgh, PA USA 	       http://www.andrew.cmu.edu/~mzk |
\-------------------------------------------------------------/