An L-System example

[villares]

I have been teaching this in so many classes over the years, and about 4 times this month 😄. Also, this is perfect for tweaking with the wonderful new Live Coding feature 😉 !

I really like doing L-Systems with Python + Processing, I always felt like my dict approach to the substitution rules was far better than the rules with arrays in Processing Java examples.

import py5

step = 8
axiom = 'F'
rules = {
    'F': 'FF+[+F-F-FO]-[-F+F+FO]',
    }
angle = 22.5
iterations = 4

def setup():
    py5.size(600, 600, py5.P3D)  # canvas 3D
    calculate_sequence()

def calculate_sequence():
    global sequence
    starting_sequence = axiom
    for i in range(iterations):
        sequence = ''
        for symbol in starting_sequence:
            sequence = sequence + rules.get(symbol, symbol)
        starting_sequence = sequence
    print(len(sequence))
    
def draw():
    #global angle
    #angle = py5.mouse_x / 5
    py5.background(240)
    py5.translate(py5.width / 2, py5.height - 50)
    py5.rotate_y(py5.frame_count / 30) # the main rotation on Y
    
    for symbol in sequence:
        if symbol == 'F':
            py5.line(0, 0, 0, -step)
            py5.translate(0, -step)
            py5.rotate_y(py5.radians(angle)) # every line twists
        elif symbol == '+':
            py5.rotate(py5.radians(-angle))
        elif symbol == '-':
            py5.rotate(py5.radians(angle))
        elif symbol == '[':
            py5.push_matrix()
        elif symbol == ']':
            py5.pop_matrix()
        elif symbol == 'O':
            py5.fill(255, 0, 0)
            py5.no_stroke()
            py5.circle(0, 0, step / 2)
            py5.stroke(0)
            
        
py5.run_sketch()

To learn more about L-Systems and related stuff:

• https://en.wikipedia.org/wiki/L-system
• Przemysław Prusinkiewicz and Aristid Lindenmayer. The Algorithmic Beauty of Plants
• http://www.paulbourke.net/fractals/lsys/
• https://www.cgjennings.ca/articles/l-systems/
• A py5 imported mode example
• Inside chapter 8 of Shiffman's Nature of Code

[vsquared]

Nice work. Impressive demo.

[binitshah]

Wow, impressive!

[hx2A]

@villares , this is wonderful, and exactly what I was hoping people would use the Live Coding feature for!

[villares]

Tomorrow I'm going to present an L-System demo, so, to gear up, today I tried to find a nice variation of these rules with the red circles...

import py5

step = 10
axiom = 'F'
rules = {
#    'F': 'FF+[+F-F-FO]-[-F+F+FO]',
   'F': 'F[+F-F+FO]F[-F+F-FO]',
    }
angle = 30
iterations = 4

def setup():
    py5.size(600, 600)
    calculate_sequence()

def calculate_sequence():
    global sequence
    starting_sequence = axiom
    for i in range(iterations):
        sequence = ''
        for symbol in starting_sequence:
            sequence = sequence + rules.get(symbol, symbol)
        starting_sequence = sequence
    print(len(sequence))
    
def draw():
    #global angle
    #angle = py5.mouse_x / 5
    py5.background(0)
    py5.stroke(255)
    py5.translate(py5.width / 2, py5.height - 30)
    
    for symbol in sequence:
        if symbol == 'F':
            py5.line(0, 0, 0, -step)
            py5.translate(0, -step)
        elif symbol == '+':
            py5.rotate(py5.radians(-angle))
        elif symbol == '-':
            py5.rotate(py5.radians(angle))
        elif symbol == '[':
            py5.push_matrix()
        elif symbol == ']':
            py5.pop_matrix()
        elif symbol == 'O':
            with py5.push_style():
                py5.fill(255, 0, 0)
                py5.no_stroke()
                py5.circle(0, 0, step / 2)

def key_pressed():
    py5.save_frame('###.png')
            
        
py5.run_sketch()

[hx2A]

This looks really nice! The red circles are a nice touch.

Did you use live coding to experiment with this?

[villares]

Not this time. But I want to get back to using it more often. I have to test the code snapshot feature and compare with stuff I was also doing (triggering the saving of folders with the code and image result of some variations).